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Sample records for ion-induced structural modification

  1. Swift Heavy Ion Induced Modification of Aliphatic Polymers

    OpenAIRE

    Hossain, Umme Habiba

    2015-01-01

    In this thesis, the high energy heavy ion induced modification of aliphatic polymers is studied. Two polymer groups, namely polyvinyl polymers (PVF, PVAc, PVA and PMMA) and fluoropolymers (PVDF, ETFE, PFA and FEP) were used in this work. Polyvinyl polymers were investigated since they will be used as insulating materials in the superconducting magnets of the new ion accelerators of the planned International Facility for Antiproton and Ion Research (FAIR) at the GSI Helmholtz-Centre of Heavy I...

  2. Ag{sup +12} ion induced modifications of structural and optical properties of ZnO-PMMA nanocomposite films

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Sarla; Vijay, Y. K. [Department of Physics, University of Rajasthan, Jaipur-302055 (India); Vyas, Rishi [Department of Physics, Malaviya National Institute of Technology, Jaipur-302017 (India)

    2013-02-05

    The influence of swift heavy ion (SHI) irradiation on structural and photoluminescence (PL) properties of ZnO-PMMA nanocomposite films, prepared by solution casting method, was studied. The ZnO-PMMA nanocomposite films were irradiated using 120 MeV Ag{sup +12} ions at different fluences varying from 1 Multiplication-Sign 10{sup 11} to 1 Multiplication-Sign 10{sup 13} ions/cm{sup 2}. The intensity of the X-ray diffraction peaks is increased at the high fluence, without evolution of any new peak. A shift in absorption edge (i.e. shift in optical band gap) towards higher wavelength was observed after irradiation and PL from ZnO-PMMA nanocomposite films is found to increase up to a critical fluence and then found to be suppressed for higher fluence (1 Multiplication-Sign 10{sup 12} ion/cm{sup 2}). The change in photoluminescence after irradiation can be attributed to the change in microstructure of PMMA matrix as well as the agglomeration of ZnO nanoparticles.

  3. Ag+12 ion induced modifications of structural and optical properties of ZnO-PMMA nanocomposite films

    International Nuclear Information System (INIS)

    Sharma, Sarla; Vijay, Y. K.; Vyas, Rishi

    2013-01-01

    The influence of swift heavy ion (SHI) irradiation on structural and photoluminescence (PL) properties of ZnO-PMMA nanocomposite films, prepared by solution casting method, was studied. The ZnO-PMMA nanocomposite films were irradiated using 120 MeV Ag +12 ions at different fluences varying from 1×10 11 to 1×10 13 ions/cm 2 . The intensity of the X-ray diffraction peaks is increased at the high fluence, without evolution of any new peak. A shift in absorption edge (i.e. shift in optical band gap) towards higher wavelength was observed after irradiation and PL from ZnO-PMMA nanocomposite films is found to increase up to a critical fluence and then found to be suppressed for higher fluence (1×10 12 ion/cm 2 ). The change in photoluminescence after irradiation can be attributed to the change in microstructure of PMMA matrix as well as the agglomeration of ZnO nanoparticles.

  4. Swift heavy ion induced modification of aliphatic polymers

    International Nuclear Information System (INIS)

    Hossain, Umme Habiba

    2015-01-01

    In this thesis, the high energy heavy ion induced modification of aliphatic polymers is studied. Two polymer groups, namely polyvinyl polymers (PVF, PVAc, PVA and PMMA) and fluoropolymers (PVDF, ETFE, PFA and FEP) were used in this work. Polyvinyl polymers were investigated since they will be used as insulating materials in the superconducting magnets of the new ion accelerators of the planned International Facility for Antiproton and Ion Research (FAIR) at the GSI Helmholtz-Centre of Heavy Ion Research (GSI) in Darmstadt. In order to study ion-beam induced degradation, all polymer foils were irradiated at the GSI linear accelerator UNILAC using several projectiles (U, Au, Sm, Xe) and experimentation sites (beam lines X0 and M3) over a large fluence regime (1 x 10 10 - 5 x 10 12 ions/cm 2 ). Five independent techniques, namely infrared (FT-IR) and ultraviolet-visible (UV-Vis) spectroscopy, residual gas analysis (RGA), thermal gravimetric analysis (TGA), and mass loss analysis (ML), were used to analyze the irradiated samples. FT-IR spectroscopy revealed that ion irradiation led to the decrease of characteristic band intensities showing the general degradation of the polymers, with scission of side groups and the main backbone. As a consequence of the structural modification, new bands appeared. UV-Vis transmission analysis showed an absorption edge shift from the ultraviolet region towards the visible region indicating double bond and conjugated double bond formation. On-line massspectrometric residual gas analysis showed the release of small gaseous fragment molecules. TGA analysis gave evidence of a changed thermal stability. With ML analysis, the considerable mass loss was quantified. The results of the five complementary analytical methods show how heavy ion irradiation changes the molecular structure of the polymers. Molecular degradation mechanisms are postulated. The amount of radiation damage is found to be sensitive to the used type of ionic species. While

  5. On-line and post irradiation analysis of swift heavy ion induced modification of PMMA (polymethyl-methacrylate)

    Energy Technology Data Exchange (ETDEWEB)

    Hossain, U.H., E-mail: u.h.hossain@gsi.de [Technische Universität Darmstadt, Department of Materials Sciences, Materials Analysis, Alarich-Weiss-Str. 2, 64287 Darmstadt (Germany); GSI Helmholtz Centre for Heavy Ion Research, Materials Research, Planckstr.1, 64291 Darmstadt (Germany); Lima, V. [Technische Universität Darmstadt, Department of Materials Sciences, Materials Analysis, Alarich-Weiss-Str. 2, 64287 Darmstadt (Germany); GSI Helmholtz Centre for Heavy Ion Research, Materials Research, Planckstr.1, 64291 Darmstadt (Germany); Baake, O. [Technische Universität Darmstadt, Department of Materials Sciences, Materials Analysis, Alarich-Weiss-Str. 2, 64287 Darmstadt (Germany); Severin, D.; Bender, M. [GSI Helmholtz Centre for Heavy Ion Research, Materials Research, Planckstr.1, 64291 Darmstadt (Germany); Ensinger, W. [Technische Universität Darmstadt, Department of Materials Sciences, Materials Analysis, Alarich-Weiss-Str. 2, 64287 Darmstadt (Germany)

    2014-05-01

    The present work is part of a research program studying the swift heavy ion induced modification of aliphatic polymers with some comparable side groups, here polymethyl-methacrylate (PMMA). This paper presents a study on Fourier-transform-infrared spectroscopy (FTIR), residual gas analysis (RGA), and Ultraviolet–Visible (UV–Vis) spectroscopy of the transformations of a PMMA film under gold (Au) and uranium (U) ion irradiation in the MeV/u range in vacuum to fluences up to 3 × 10{sup 11} ions per cm{sup 2}. The results show a general ion induced degradation of the polymer, with release of volatile fragments, scission of side chains and polymeric backbone, formation of conjugated double bonds, and the resulting increased absorption of the UV part in the UV–Vis spectral region. A molecular scission mechanism which explains the main degradation products is proposed.

  6. Ion induced millimetre-scale structures growth on metal surfaces

    Science.gov (United States)

    Girka, O.; Bizyukov, O.; Balkova, Y.; Myroshnyk, M.; Bizyukov, I.; Bogatyrenko, S.

    2018-04-01

    Polished polycrystalline Plansee tungsten (W) sample with purity 99.99 wt% and 0.75 mm thickness has been exposed to intense argon (Ar) ion beam with average energy of 2 keV and etched through in the centre. As a result, castle-like structures with strong asymmetry and with the height of >200 μm have been formed. Structures can be observed by naked eyes and with scanning-electron microscopy (SEM). It has been revealed, that the structures have been formed not immediately, but at the later stages of irradiation. Primary factors favouring the formation for the structures are relaxation of the surface stresses and activated surface mobility of atoms.

  7. Ion induced changes in the structure of bordered pit membranes

    Directory of Open Access Journals (Sweden)

    Jinkee eLee

    2012-03-01

    Full Text Available Xylem hydraulic resistance varies with ion concentration in sap solution. It is assumed that this variation in resistance results from hydrogel like properties of pectins located in bordered pit membranes separating adjacent vessels. Although kinetics of the resistance change suggests swelling/deswelling behavior of the pectins, there is no direct evidence of this activity. In this report we provide evidence of structural changes in bordered pit membranes responding to variation in ionic concentration of solute around it using atomic force microscopy (AFM. AFM revealed bordered pit membranes as relatively smooth, soft and lacking any sharp edges surface when submerged in de-ionized water, in contrast to pictures from scanning electron microscope (SEM or AFM performed on air dry material. Exposure of the bordered pit membranes to 50 mM KCl solution resulted in significant changes in both surface physical properties with and elevation features as bordered pit membrane became harder, with visible edges of fibers and collapsed, while no change in porosity was observed. Analysis suggests a need for a major shift in our understanding to the physical bases of variable xylem resistance from change in porosity to change in pathway length. Findings support the role of actuating properties of hybrid hydrogel-cellulose materials in water redistribution and embolism resistance.

  8. Swift heavy ion induced modifications in optical and electrical properties of cadmium selenide thin films

    Science.gov (United States)

    Choudhary, Ritika; Chauhan, Rishi Pal

    2017-07-01

    The modification in various properties of thin films using high energetic ion beam is an exciting area of basic and applied research in semiconductors. In the present investigations, cadmium selenide (CdSe) thin films were deposited on ITO substrate using electrodeposition technique. To study the swift heavy ion (SHI) induced effects, the deposited thin films were irradiated with 120 MeV heavy Ag9+ ions using pelletron accelerator facility at IUAC, New Delhi, India. Structural phase transformation in CdSe thin film from metastable cubic phase to stable hexagonal phase was observed after irradiation leading to decrease in the band gap from 2.47 eV to 2.12 eV. The phase transformation was analyzed through X-ray diffraction patterns. During SHI irradiation, Generation of high temperature and pressure by thermal spike along the trajectory of incident ions in the thin films might be responsible for modification in the properties of thin films.[Figure not available: see fulltext.

  9. 60 MeV Ni ion induced modifications in nano-CdS/polystyrene composite films

    Science.gov (United States)

    Kumar, Satyendra; Singh, Paramjit; Sonkawade, R. G.; Awasthi, Kamlendra; Kumar, Rajesh

    2014-01-01

    The cadmium sulfide (CdS) nanoparticles of size in the range 50-60 nm were synthesized by micro-emulsion method. The polystyrene/CdS (PS/CdS) nanocomposites were doped with Ni and Cu metals. The pristine and doped samples were irradiated with 60 MeV Ni ions. The effect of doping of metals and ion irradiation was studied for modifications in structural, optical and chemical properties of PS/CdS nanocomposites. The decrease in peak width of XRD spectra of irradiated PS indicated the decrease in the amorphous nature at higher fluences. The optical absorption peaks of the irradiated and doped samples shifted towards visible region. The shift in case of metal doped samples was more pronounced than those of pure polystyrene and PS/CdS matrix samples. The increase in absorption was attributed to the generation of a conjugated system of bonds. The decrease in band gap energy value in case of Ni doped PS/CdS was greater than that of Cu doped PS/CdS and the ion irradiation further decreased the band gap energy value. The vibrational absorption peak of the Cd-S bond was observed at 405 cm-1 in FTIR spectra of metal doped PS/CdS composites. The intensity of styrene absorption lines decreased in all irradiated samples.

  10. In situ analysis of ion-induced polymer surface modification using secondary ion mass spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Okuji, Shigeto, E-mail: s-okuji@post.lintec.co.jp [Lintec Corporation, 5-14-42 Nishiki-cho, Warabi, Saitama 335-0005 (Japan); Quantum Beam Unit, National Institute for Materials Science, 3-13 Sakura, Tsukuba, Ibaraki 305-0003 (Japan); University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan); Kitazawa, Hideaki [Quantum Beam Unit, National Institute for Materials Science, 3-13 Sakura, Tsukuba, Ibaraki 305-0003 (Japan); Takeda, Yoshihiko, E-mail: TAKEDA.Yoshihiko@nims.go.jp [Quantum Beam Unit, National Institute for Materials Science, 3-13 Sakura, Tsukuba, Ibaraki 305-0003 (Japan); University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577 (Japan)

    2016-06-15

    We have investigated the surface modification process consisting of ion irradiation immediately followed by exposure to ambient gas for three types of polymers having the same main chain, −C−C−, but different atoms bound to the main chain, using in situ secondary ion mass spectroscopy. The polymers’ surface was irradiated with 30 keV Au ions at a total fluence for up to 1 × 10{sup 17} cm{sup −2} and exposed to ambient gas in a ultra-high-vacuum chamber (1 × 10{sup −6} Pa) for 30 min after the ion irradiation. Low density polyethylene mainly exhibited a hydrogen dissociation during the ion irradiation and a recombination with hydrogen atoms by the exposure, polytetrafluoroethylene mainly showed a main chain scission and no recombination during the exposure, and polyvinylidene difluoride lost hydrogen and fluorine atoms by the ion irradiation and partially recombined with hydrogen and fluorine atoms upon the exposure. The deposited energy density on the polymer surfaces reflects the dependence of the modification on the incident ion species, Au or Ga ions.

  11. Structural dynamic modification

    Indian Academy of Sciences (India)

    In this paper, the direct problem of determing the new response of a system, after some modifications are introduced into the sestem, is analysed using two different databases: the modal database and the frequency response function database. The limitaions of the modal database are discussed. Structural modifications ...

  12. Structural dynamic modification

    Indian Academy of Sciences (India)

    for are lumped masses, springs, dampers and dynamic absorbers. Keywords. Structural dynamic modification; structural design; dynamic design; SDM using FRF. 1. Introduction. The problem of varying the dynamic behaviour of structures to reduce the vibration response or control the noise radiated by vibrating surfaces is ...

  13. Structural dynamic modification

    Indian Academy of Sciences (India)

    5th Int. Modal Anal. Conf. (London) 2: 1538±1544. Sestieri A, D'Ambrogio W 1988 Why be model: i.e. how to avoid the use of modes in the modification of vibrating systems. Proc. 6th Int. Modal Anal. Conf. (Orlando) 2: 1100±1106. Sestieri A, D'Ambrogio W 1989 A modification method for vibration control of structures. Mech.

  14. Swift heavy ions induced surface modifications in Ag-polypyrrole composite films synthesized by an electrochemical route

    International Nuclear Information System (INIS)

    Kumar, Vijay; Ali, Yasir; Sharma, Kashma; Kumar, Vinod; Sonkawade, R.G.; Dhaliwal, A.S.; Swart, H.C.

    2014-01-01

    Highlights: • Two steps electrochemical synthesis for the fabrication of Ag-polypyrrole composite films. • Surface modifications by swift heavy ion beam. • SEM image shows the formation of craters and humps after irradiation. • Detailed structural analysis by Raman spectroscopy. - Abstract: The general aim of this work was to study the effects of swift heavy ions on the properties of electrochemically synthesized Ag-polypyrrole composite thin films. Initially, polypyrrole (PPy) films were electrochemically synthesized on indium tin oxide coated glass surfaces using a chronopotentiometery technique, at optimized process conditions. The prepared PPy films have functioned as working electrodes for the decoration of submicron Ag particles on the surface of the PPy films through a cyclicvoltammetry technique. Towards probing the effect of swift heavy ion irradiation on the structural and morphological properties, the composite films were subjected to a 40 MeV Li 3+ ion beam irradiation for various fluences (1 × 10 11 , 1 × 10 12 and 1 × 10 13 ions/cm 2 ). Comparative microstructural investigations were carried out after the different ion fluences using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy and micro-Raman spectroscopy techniques. Raman and SEM studies revealed that the structure of the films became disordered after irradiation. The SEM studies of irradiated composite films show significant changes in their surface morphologies. The surface was smoother at lower fluence but craters were observed at higher fluence

  15. Swift heavy ions induced surface modifications in Ag-polypyrrole composite films synthesized by an electrochemical route

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Vijay, E-mail: vijays_phy@rediffmail.com [Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA 9300 (South Africa); Ali, Yasir [Department of Physics, Sant Longowal Institute of Engineering and Technology, Longowal, District Sangrur 148106, Punjab (India); Sharma, Kashma [Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA 9300 (South Africa); Department of Chemistry, Shoolini University of Biotechnology and Management Sciences, Solan 173212 (India); Kumar, Vinod [Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA 9300 (South Africa); Sonkawade, R.G. [Inter University Accelerator Center, Aruna Asif Ali Marg, New Delhi 110067 (India); Dhaliwal, A.S. [Department of Physics, Sant Longowal Institute of Engineering and Technology, Longowal, District Sangrur 148106, Punjab (India); Swart, H.C., E-mail: swarthc@ufs.ac.za [Department of Physics, University of the Free State, P.O. Box 339, Bloemfontein ZA 9300 (South Africa)

    2014-03-15

    Highlights: • Two steps electrochemical synthesis for the fabrication of Ag-polypyrrole composite films. • Surface modifications by swift heavy ion beam. • SEM image shows the formation of craters and humps after irradiation. • Detailed structural analysis by Raman spectroscopy. - Abstract: The general aim of this work was to study the effects of swift heavy ions on the properties of electrochemically synthesized Ag-polypyrrole composite thin films. Initially, polypyrrole (PPy) films were electrochemically synthesized on indium tin oxide coated glass surfaces using a chronopotentiometery technique, at optimized process conditions. The prepared PPy films have functioned as working electrodes for the decoration of submicron Ag particles on the surface of the PPy films through a cyclicvoltammetry technique. Towards probing the effect of swift heavy ion irradiation on the structural and morphological properties, the composite films were subjected to a 40 MeV Li{sup 3+} ion beam irradiation for various fluences (1 × 10{sup 11}, 1 × 10{sup 12} and 1 × 10{sup 13} ions/cm{sup 2}). Comparative microstructural investigations were carried out after the different ion fluences using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy and micro-Raman spectroscopy techniques. Raman and SEM studies revealed that the structure of the films became disordered after irradiation. The SEM studies of irradiated composite films show significant changes in their surface morphologies. The surface was smoother at lower fluence but craters were observed at higher fluence.

  16. Ion induced modification of polymers at energies between 100 keV and 1 GeV applied for optical waveguides and improved metal adhesion

    International Nuclear Information System (INIS)

    Rueck, D.M.

    2000-01-01

    Polymers are a class of materials widely used for a broad field of applications. Ion irradiation ranging from several eV to GeV is a quite efficient tool to modify the properties of polymers like wettability, optical properties, adhesion between metal and polymer surfaces. In this paper ion induced chemical changes of polymers will be discussed in relation to the modified macroscopic properties. In the field of optical telecommunication, polymers are discussed as a new class of materials for the fabrication of passive optical devices. Ion irradiation is a promising method to generate structures with a modified index of refraction, which is necessary for the guidance of light with different wavelengths in optical devices. Modified optical properties of different polymers under ion irradiation will be discussed. Analytical investigations like infrared measurements and measurement of the outgassing reaction products during irradiation will be discussed to interpret the chemical changes of the polymers. Metallization of polymers is of interest in several fields of application like for multilayer systems in microtechnology or casings for radiation shielding for example. Ion beam mixing at low energies is a promising method to improve the metal/polymer adhesion. Also ion irradiation at high energies applied to a metal/polymer multilayer can improve the adhesion of a metal layer to a polymer surface, if not sufficient. Different metal/polymer systems will be presented as well as specific applications

  17. Structural changes of DNA in heavy ion-induced mutants on Arabidopsis

    Energy Technology Data Exchange (ETDEWEB)

    Tano, S.; Shikazono, N.; Tanaka, A.; Yokota, Y.; Watanabe, H. [Japan Atomic Research Research Inst., Watanuki, Takasaki (Japan). Advanced Science Research Center

    1997-09-01

    In order to investigate the frequency of structural changes induced by high LET radiation in plants, a comparison was made between DNA fragments amplified by the polymerase chain reaction (PCR) from C ion- and electron-induced Arabidopsis mutants at GL and TT loci. (orig./MG)

  18. Structural changes of DNA in heavy ion-induced mutants on Arabidopsis

    International Nuclear Information System (INIS)

    Tano, S.; Shikazono, N.; Tanaka, A.; Yokota, Y.; Watanabe, H.

    1997-01-01

    In order to investigate the frequency of structural changes induced by high LET radiation in plants, a comparison was made between DNA fragments amplified by the polymerase chain reaction (PCR) from C ion- and electron-induced Arabidopsis mutants at GL and TT loci. (orig./MG)

  19. Structural dynamic modifications via models

    Indian Academy of Sciences (India)

    2nd Int. Modal Analysis Conference (Orlando) 2: 930±936. Natke H G (ed.) 1982 Identification of vibrating structures (New York: Springer Verlag, Wein). Rao S S 1989 Optimum design of structures under shock and vibration environment. Shock Vibr. Dig. 21(7):. Ravi S S A 1994 Structural dynamic modifications and design ...

  20. Photothermal modification of plasmonic structures

    DEFF Research Database (Denmark)

    2016-01-01

    at least a portion of each of the plasmonic structures within the second plurality of plasmonic structures by irradiating, the plasmonic structures with incident electromagnetic radiation having an incident intensity in a plane of the second plurality of plasmonic structures, wherein said incident...

  1. Structural dynamic modifications via models

    Indian Academy of Sciences (India)

    of structural dynamic optimization techniques. A review of structural optimization in vibratory environments is given by Rao (1989). 2. SDM techniques. SDM methods may be broadly divided into two groups. Those which employ a model of the structure and those that use dynamic test data directly. The model used by the ...

  2. Structural dynamic modification using additive damping

    Indian Academy of Sciences (India)

    In order to control dynamic response in structures and machines, modofications using additive viscoelastic damping materials are highlighted. The techniques described for analysis include analytical methods for structural elements, FEM and perturbation methods for reanalysis or structural dynamic modifications for ...

  3. Ion-induced surface modification of alloys

    International Nuclear Information System (INIS)

    Wiedersich, H.

    1983-11-01

    In addition to the accumulation of the implanted species, a considerable number of processes can affect the composition of an alloy in the surface region during ion bombardment. Collisions of energetic ions with atoms of the alloy induce local rearrangement of atoms by displacements, replacement sequences and by spontaneous migration and recombination of defects within cascades. Point defects form clusters, voids, dislocation loops and networks. Preferential sputtering of elements changes the composition of the surface. At temperatures sufficient for thermal migration of point defects, radiation-enhanced diffusion promotes alloy component redistribution within and beyond the damage layer. Fluxes of interstitials and vacancies toward the surface and into the interior of the target induce fluxes of alloying elements leading to depth-dependent compositional changes. Moreover, Gibbsian surface segregation may affect the preferential loss of alloy components by sputtering when the kinetics of equilibration of the surface composition becomes competitive with the sputtering rate. Temperature, time, current density and ion energy can be used to influence the individual processes contributing to compositional changes and, thus, produce a rich variety of composition profiles near surfaces. 42 references

  4. Structural modifications leading to changes in supramolecular ...

    Indian Academy of Sciences (India)

    1347–1356. c Indian Academy of Sciences. Structural modifications leading to changes in supramolecular aggregation of thiazolo[3, 2-a]pyrimidines: Insights into their conformational features. H NAGARAJAIAH and NOOR SHAHINA BEGUM. ∗. Department of Studies in Chemistry, Bangalore University, Bangalore 560 001, ...

  5. Ion-induced nuclear radiotherapy

    Science.gov (United States)

    Horn, K.M.; Doyle, B.L.

    1996-08-20

    Ion-induced Nuclear Radiotherapy (INRT) is a technique for conducting radiosurgery and radiotherapy with a very high degree of control over the spatial extent of the irradiated volume and the delivered dose. Based upon the concept that low energy, ion induced atomic and nuclear reactions can be used to produce highly energetic reaction products at the site of a tumor, the INRT technique is implemented through the use of a conduit-needle or tube which conducts a low energy ion beam to a position above or within the intended treatment area. At the end of the conduit-needle or tube is a specially fabricated target which, only when struck by the ion beam, acts as a source of energetic radiation products. The inherent limitations in the energy, and therefore range, of the resulting reaction products limits the spatial extent of irradiation to a pre-defined volume about the point of reaction. Furthermore, since no damage is done to tissue outside this irradiated volume, the delivered dose may be made arbitrarily large. INRT may be used both as a point-source of radiation at the site of a small tumor, or as a topical bath of radiation to broad areas of diseased tissue. 25 figs.

  6. Progress on nuclear modifications of structure functions

    Directory of Open Access Journals (Sweden)

    Kumano S.

    2016-01-01

    Full Text Available We report progress on nuclear structure functions, especially on their nuclear modifications and a new tensor structure function for the deuteron. To understand nuclear structure functions is an important step toward describing nuclei and QCD matters from low to high densities and from low to high energies in terms of fundamental quark and gluon degrees of freedom beyond conventional hadron and nuclear physics. It is also practically important for understanding new phenomena in high-energy heavy-ion collisions at RHIC and LHC. Furthermore, since systematic errors of current neutrinooscillation experiments are dominated by uncertainties of neutrino-nucleus interactions, such studies are valuable for finding new physics beyond current framework. Next, a new tensor-polarized structure function b1 is discussed for the deuteron. There was a measurement by HERMES; however, its data are inconsistent with the conventional convolution estimate based on the standard deuteron model with D-state admixture. This fact suggests that a new hadronic phenomenon should exist in the tensor-polarized deuteron at high energies, and it will be experimentally investigated at JLab from the end of 2010’s.

  7. Ion induced dipole clusters H(n)- (3 ≤ n-odd ≤ 13): density functional theory calculations of structure and energy.

    Science.gov (United States)

    Huang, Lulu; Matta, Chérif F; Massa, Lou

    2011-11-17

    We investigate anew the possible equilibrium geometries of ion induced dipole clusters of hydrogen molecular ions, of molecular formula H(n)(-) (3 ≤ n-odd ≤ 13). Our previous publications [Sapse, A. M.; et al. Nature 1979, 278, 332; Rayez, J. C.; et al., J. Chem. Phys. 1981, 75, 5393] indicated these molecules would have a shallow minimum and adopt symmetrical geometries that accord with the valence shell electron pair repulsion (VSEPR) rules for geometries defined by electron pairs surrounding a central point of attraction. These earlier calculations were all based upon Hartree-Fock (HF) calculations with a fairly small basis of atomic functions, except for the H3(-) ion for which configuration interaction (CI) calculations were carried out. A related paper [Hirao, K.; et al., Chem. Phys. 1983, 80, 237] carried out similar calculations on the same clusters, finding geometries similar to our earlier calculations. However, although that paper argued that the stabilization energy of negative ion clusters H(n)(-) is small, vibration frequencies for the whole set of clusters was not reported, and so a definitive assertion of a true equilibrium was not present. In this paper we recalculate the energetics of the ion induced dipole clusters using density function theory (DFT) B3LYP method calculations in a basis of functions (6-311++G(d,p)). By calculating the vibration frequencies of the VSEPR geometries, we prove that in general they are not true minima because not all the resulting frequencies correspond to real values. By searching the energy surface of the B3LYP calculations, we find the true minimum geometries, which are surprising configurations and are perhaps counterintuitive. We calculate the total energy and binding energy of the new geometries. We also calculate the bond paths associated with the quantum theory of atoms in molecules (QTAIM). The B3LYP/6-311++G(d,p) results, for each molecule, deliver bond paths that radiate between each polarized H2

  8. Structural modifications of spinels under radiation

    International Nuclear Information System (INIS)

    Quentin, A.

    2010-12-01

    This work is devoted to the study of spinel structure materials under radiation. For that purpose, samples of polycrystalline ZnAl 2 O 4 and monocrystalline MgAl 2 O 4 were irradiated by different heavy ions with different energies. Samples of ZnAl 2 O 4 were studied par electron transmission microscopy, and by grazing incidence X-Ray diffraction and Rietveld analysis. Samples of MgAl 2 O 4 were studied by optical spectroscopy. Most of the results concern amorphization and crystalline structure modification of ZnAl 2 O 4 especially the inversion. We were able to determine a stopping power threshold for amorphization, between 11 keV/nm and 12 keV/nm, and also the amorphization process, which is a multiple impacts process. We studied the evolution of the amorphous phase by TEM and showed a nano-patterning phenomenon. Concerning the inversion, we determined that it did happen by a single impact process, and the saturation value did not reach the random cation distribution value. Inversion and amorphization have different, but close, stopping power threshold. However, amorphization seems to be conditioned by a pre-damage of the material which consists in inversion. (author)

  9. A study of the physical mechanisms responsible for heavy ion-induced latent defects in gate oxides

    International Nuclear Information System (INIS)

    Portier, M.

    2010-01-01

    Heavy ions naturally present in the radiation environment of space is a constraint to take into account for embedded electronics. It was observed that heavy ions induce nano-scale structural modifications in the oxide of the SiO 2 -Si structures. SiO 2 -Si structures were representative of the MOS devices embedded. These structural modifications induced by heavy ions can play the role of latent defects in embedded MOSFETs observed by the premature breakdown in the gate oxide of MOS power transistors during function, thus reducing their lifetime. From a statistical study of our topographic structures irradiated, we seek to highlight the parameters to take into account to better understand the physical mechanisms behind the formation of the latent defects. We would to give a full account of reality relating to the probability of formation in order to establish a full evaluation of the risks linked to these defects. It is with a better knowledge of training criteria. (author)

  10. Ion-induced effects on metallic nanoparticles

    International Nuclear Information System (INIS)

    Klimmer, Andreas

    2010-01-01

    This work deals with the ion-irradiation of metallic nanoparticles in combination with various substrates. Particle diameters were systematically varied within the range of 2.5-14 nm, inter-particle distances range from 30-120 nm. Irradiations were performed with various inert gas ions with energies of 200 keV, resulting in an average ion range larger than the particle dimensions and therefore the effects of irradiation are mainly due to creation of structural defects within the particles and the underlying substrate as well. The main part of this work deals with ion-induced burrowing of metallic nanoparticles into the underlying substrate. The use of micellar nanoparticles with sharp size distribution combined with AFM and TEM analysis allows a much more detailed look at this effect than other works on that topic so far. With respect to the particle properties also a detailed look on the effect of irradiation on the particle structure would be interesting, which might lead to a deliberate influence on magnetic properties, for example. Within the context of this work, first successful experiments were performed on FePt particles, showing a significant reduction of the ordering temperature leading to the magnetically interesting, ordered L1 0 phase. (orig.)

  11. The role of ammonia in sulfuric acid ion induced nucleation

    Directory of Open Access Journals (Sweden)

    I. K. Ortega

    2008-06-01

    Full Text Available We have developed a new multi-step strategy for quantum chemical calculations on atmospherically relevant cluster structures that makes calculation for large clusters affordable with a good accuracy-to-computational effort ratio. We have applied this strategy to evaluate the relevance of ternary ion induced nucleation; we have also performed calculations for neutral ternary nucleation for comparison. The results for neutral ternary nucleation agree with previous results, and confirm the important role of ammonia in enhancing the growth of sulfuric acid clusters. On the other hand, we have found that ammonia does not enhance the growth of ionic sulfuric acid clusters. The results also confirm that ion-induced nucleation is a barrierless process at high altitudes, but at ground level there exists a barrier due to the presence of a local minimum on the free energy surface.

  12. Assembling Metal Ions Induced Cyanide-Bridged Heterometallic 1D and Ion-Pair Complexes: Synthesis, Crystal Structures and Magnetic Properties

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Lingqian [Liaocheng Univ., Liaocheng (China); Zhao, Zengdian; Chen, Kexun; Wang, Ping; Zhang, Daopeng [Shandong Univ. of Technology, Zibo (China)

    2013-07-15

    We obtained a heterobimetallic one-dimensional cyanide-bridged Mn(II)-Ni(II) complex and an Co(III)-Ni(II) ion-pair complex with [Ni(CN){sub 4}]{sup 2-} as building block and M(II)-phenanthroline (M = Mn, Co) compounds as assembling segment. The different structural types of complexes 1 and 2 indicate that the property of the metal ions the assembling segment contained have obvious influence on the structure of the cyanide-bridged complex. Investigation over the magnetic properties of complex 1 reveals an overall weak antiferromagnetic coupling between the adjacent Mn(II) ions bridged by the antiferromagnetic [-NC-Ni-CN-] unit. Among of all the molecular magnetism systems, for the well known reasons, cyanide-containing complexes have been widely employed as bridges to assemble homo/hetero-metallic molecular magnetic materials by using the cyanide bridge transferring magnetic coupling between the neighboring paramagnetic ions, in whichsome showed interesting magnetic properties, such as high-Tc magnets, spin crossover materials, single-molecule magnets (SMMs) and single-chain magnets (SCMs)

  13. Structural studies of the melibiose permease of Escherichia coli by fluorescence resonance energy transfer. I. Evidence for ion-induced conformational change.

    Science.gov (United States)

    Maehrel, C; Cordat, E; Mus-Veteau, I; Leblanc, G

    1998-12-11

    Further insight into the cosubstrate-induced structural change of the melibiose permease (MelB) of Escherichia coli has been sought by investigating the binding and spectroscopic properties of the fluorescent sugar 2'-(N-5-dimethylaminonaphthalene-1-sulfonyl)aminoethyl 1-thio-beta-D-galactopyranoside (Dns2-S-Gal) and related analogs (Dns3-S-Gal or Dns6-S-Gal with a propyl or hexyl instead of an ethyl linker, respectively) interacting with MelB in membrane vesicles or in proteoliposomes. The three analogs efficiently inhibit melibiose transport and bind to MelB in a sodium-dependent fashion. Their dissociation constants (Kd) are in the micromolar range in the presence of NaCl and an order of magnitude higher in its absence. In the presence of NaCl and Dns2-S-Gal, sample excitation at 335 or 297 nm gives rise to a fluorescent signal at around 465 nm, whereas Dns3-S-Gal or Dns6-S-Gal emits a fluorescence light at 490 or 506 nm, respectively. Detailed study of the Dns2-S-Gal signal elicited by a 297 nm illumination indicates that a tryptophan-mediated fluorescence resonance energy transfer phenomenon is involved in the response. All fluorescence signals below 500 nm are prevented by addition of melibiose in excess, and the kinetic constants describing their dependence on the probe or NaCl concentrations closely correlate with the probe binding constants. Finally, the Dns2-S-Gal signal recorded in sodium-free medium is red shifted by up to 25 nm from that recorded in the presence of NaCl. Taken together, these results suggest (i) that the fluorescence signals below 500 nm arise from Dns-S-Gal molecules bound to MelB, (ii) the presence of a highly hydrophobic environment close to or at the sugar-binding site, the polarity of which increases on moving away from the sugar-binding site, and (iii) that the interaction of sodium ions with MelB enhances the hydrophobicity of this environment. These results are consistent with the induction of a cooperative change of the

  14. Genetic modification and its impact on industry structure and performance

    NARCIS (Netherlands)

    Vlaar, P.W.L.; van Beek, P.; Visser, R.G.F.

    2007-01-01

    Genetic modification has led to fierce debates around the world. Nevertheless, scientific evidence for its potential effects on the structure and performance of industries has hitherto remained rather meagre. In this article, we take some preliminary steps towards closing this gap by exploring the

  15. The effect of structured counselling on lifestyle modification ...

    African Journals Online (AJOL)

    Aim: The study was undertaken to determine the effect of structured counseling on lifestyle modification measures among adult hypertensive patients. Methods: The study was a randomized controlled trial involving hypertensive adults aged 20 years and above presenting in GOPC of JUTH. Participants were consecutively ...

  16. Investigation of ion induced bending mechanism for nanostructures

    Science.gov (United States)

    Rajput, Nitul S.; Tong, Zhen; Luo, Xichun

    2015-01-01

    Ion induced bending is a promising controlled technique for manipulating nanoscale structures. However, the underlying mechanism of the process is not well understood. In this letter, we report a detailed study of the bending mechanism of Si nanowires (NWs) under Ga+ irradiation. The microstructural changes in the NW due to ion beam irradiation are studied and molecular dynamics simulations are used to explore the ion-NW interaction processes. The simulation results are compared with the microstructural studies of the NW. The investigations inform a generic understanding of the bending process in crystalline materials, which we suggest to be feasible as a versatile manipulation and integration technique in nanotechnology.

  17. Chemical modification of citrus pectin: Structural, physical and rheologial implications.

    Science.gov (United States)

    Fracasso, Aline Francielle; Perussello, Camila Augusto; Carpiné, Danielle; Petkowicz, Carmen Lúcia de Oliveira; Haminiuk, Charles Windson Isidoro

    2018-04-01

    The present study aimed to investigate the physical, structural and rheological modifications caused by the chemical modification process of citrus pectin. Therefore, three commercial citrus pectins with different degree of esterification were chemically modified by sequential alkali and acidic hydrolytic process to produce modified citrus pectins (MCP) with special properties. The molar mass (M w ), degree of esterification (DE), monosaccharide composition, 13 C NMR spectra, homogeneity, morphology (SEM) and rheological behavior of both native and modified citrus pectins (MCP) were investigated. The chemical modification reduced the acid uronic content (up to 28.3%) and molar mass (up to 29.98%), however, showed little influence on the degree of esterification of native pectins. Modified citrus pectins presented higher amounts of neutral monosaccharides, mainly galactose, arabinose and rhamnose, typical of the Ramnogalacturonana-I (RG-I) region. Rheological tests indicated that the native and modified citrus pectins presented pseudoplastic behavior, however, the MCP samples were less viscous, compared to the native ones. Modified samples presented better dissolution in water and less strong gels, with good stability during oscillatory shearing at 25°C. This study aims to better understand the implications that chemical modifications may impose on the structure of citrus pectins. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Heavy-ion induced fission reactions

    International Nuclear Information System (INIS)

    Britt, H.C.; Fowler, M.M.; Fraenkel, Z.; Gavron, A.; Plicht, J.; Wilhelmy, J.B.; Plasil, F.; Awes, T.; Young, G.

    1983-01-01

    Heavy-ion induced fission reactions are investigated. The problem of obtaining a representative set of fission-cross section data, so that it would be possible to test both the mass and angular momentum dependence of fission barriers in the mass region 150 9 Be through 64 Ni. The experimental data clearly show the qualitative effects of angular momentum, excitation energy and fissility on the fission cross section. They provide an ideal testing ground for theoretical models of fission in this mass region

  19. Fouling Kinetics and Associated Dynamics of Structural Modifications

    DEFF Research Database (Denmark)

    Jacob, Jerome; Prádanos, Pedro; Calvo, J. I.

    1998-01-01

    It is shown that the fouling behaviour of microfiltration membranes does not agree within all the time ranges of any of the commonly used membrane blocking models (i.e. complete, standard, intermediate or cake blocking). The resulting experimental kinetics of flux decline do not fit to only one...... of these models, but according to a successive or simultaneous coexistence of two or more of them. This is studied by analysing the structural modifications associated with the fouling kinetics. To achieve this goal, here we analyse the dynamical changes on the structure of four microporous membranes made...... by Sartorius (ST02 and ST045, neutral) and Spectrum (SP02 and SP045, positively charged) when fouled by permeating a protein aqueous solution (bovine serum albumin (BSA) at 1 g l(-1)) under 10 kPa in a dead-end device. The structure after different fouling times is obtained by using an extended bubble point...

  20. Strengthening, modification and repair techniques’ prioritization for structural integrity control of ageing offshore structures

    International Nuclear Information System (INIS)

    Samarakoon, Samindi M.K.; Ratnayake, R.M. Chandima

    2015-01-01

    Structural integrity control is vital for existing ageing as well as newly built offshore and onshore structures. Structural integrity control becomes highly sensitive to interventions under a potential loss of structural integrity when it comes to offshore oil and gas production and process facilities. This is mainly due to the inherent constraints present in carrying out engineering work in the offshore atmosphere. It has been further exacerbated by the ageing offshore structures and the necessity of carrying out life extension toward the end of their design service lives. Local and international regulations demand the implementation of appropriate strengthening, modification and repair plans when significant changes in the structural integrity are revealed. In this context, strengthening, modification and repair techniques such as welding, member removal/reduction of loading, mechanical clamping and grouted repairs play a vital role. This manuscript presents an approach for prioritizing the strengthening, modification and repair techniques using a multi-criteria analysis approach. An analytic hierarchy process has been selected for the analysis via an illustrative case. It also provides a comprehensive overview of currently existing; strengthening, modification and repair techniques and their comparative pros and cons. - Highlights: • Structural integrity control (SIC) of ageing and intact offshore structures. • Strengthening, modification and/or repair (SMR) techniques have been explained. • Application of multi-criteria analysis conserving SI has been illustrated. • SMR techniques prioritization and sensitivity analysis has been performed

  1. Characterization of carbon ion-induced mutations in Arabidopsis thaliana

    International Nuclear Information System (INIS)

    Shikazono, N.; Suzuki, C.; Kitamura, S.; Watanabe, H.; Tano, S.; Tanaka, A.

    2003-01-01

    Full text: Irradiation of Arabidopsis thaliana by carbon ions was carried out to investigate the mutational effect of ion particles in higher plants. The averaged mutation rate of carbon ions was 2.0 X 10 -6 / Gy, which was 18-fold higher than that of electrons. PCR analysis of the carbon ion-induced mutants showed that, out of 28 mutant alleles, 14 had point-like mutations within the gene, while 14 contained large structural alterations. In the case of 12 electron-induced mutants, 9 had point-like mutations within the gene, while 3 contained large structural alterations. These results suggest that carbon ions are more likely to induce large structural alterations compared with electrons. Further sequence analysis revealed that most of the point-like mutations induced by carbon ions were short deletions. In the case of rearrangements, DNA strand breaks were found to be rejoined using, if present, short homologous sequences for both types of radiation. After carbon ion-irradiation, small deletions were frequently observed around the breakpoints, whereas duplications of terminal sequence were found after electron-irradiation. These results suggest that non-homologous end joining (NHEJ) pathway operates after plant cells are exposed to both ion particles and electrons but that different mode of rejoining deals with the broken ends produced by each radiation. From the present results, it seems reasonable to assume that carbon ions could predominantly induce null mutations in Arabidopsis. The fact that the molecular nature of carbon ion-induced mutation was different from that of electrons and that the molecular mechanisms of cells to induce mutations appeared to be also different implicates that ion particle is not only valuable as a new mutagen but also useful as a new tool to study repair mechanisms of certain types of DNA damage

  2. Heavy-ion induced current through an oxide layer

    International Nuclear Information System (INIS)

    Takahashi, Yoshihiro; Ohki, Takahiro; Nagasawa, Takaharu; Nakajima, Yasuhito; Kawanabe, Ryu; Ohnishi, Kazunori; Hirao, Toshio; Onoda, Shinobu; Mishima, Kenta; Kawano, Katsuyasu; Itoh, Hisayoshi

    2007-01-01

    In this paper, the heavy-ion induced current in MOS structure is investigated. We have measured the transient gate current in a MOS capacitor and a MOSFET induced by single heavy-ions, and found that a transient current can be observed when the semiconductor surface is under depletion condition. In the case of MOSFET, a transient gate current with both positive and negative peaks is observed if the ion hits the gate area, and that the total integrated charge is almost zero within 100-200 ns after irradiation. From these results, we conclude that the radiation-induced gate current is dominated by a displacement current. We also discuss the generation mechanism of the radiation-induced current through the oxide layer by device simulation

  3. Ions-induced nanostructuration: effect of specific ionic adsorption on hydrophobic polymer surfaces.

    Science.gov (United States)

    Siretanu, Igor; Chapel, Jean-Paul; Bastos-González, Delfi; Drummond, Carlos

    2013-06-06

    The effect of surface charges on the ionic distribution in close proximity to an interface has been extensively studied. On the contrary, the influence of ions (from dissolved salts) on deformable interfaces has been barely investigated. Ions can adsorb from aqueous solutions on hydrophobic surfaces, generating forces that can induce long-lasting deformation of glassy polymer films, a process called ion-induced polymer nanostructuration, IPN. We have found that this process is ion-specific; larger surface modifications are observed in the presence of water ions and hydrophobic and amphiphilic ions. Surface structuration is also observed in the presence of certain salts of lithium. We have used streaming potential and atomic force microscopy to study the effect of dissolved ions on the surface properties of polystyrene films, finding a good correlation between ionic adsorption and IPN. Our results also suggest that the presence of strongly hydrated lithium promotes the interaction of anions with polystyrene surfaces and more generally with hydrophobic polymer surfaces, triggering then the IPN process.

  4. Modification of nanofibrillated cellulose using amphiphilic block-structured galactoglucomannans.

    Science.gov (United States)

    Lozhechnikova, Alina; Dax, Daniel; Vartiainen, Jari; Willför, Stefan; Xu, Chunlin; Österberg, Monika

    2014-09-22

    Nanofibrillated cellulose (NFC) and hemicelluloses have shown to be highly promising renewable components both as barrier materials and in novel biocomposites. However, the hydrophilic nature of these materials restricts their use in some applications. In this work, the usability of modified O-acetyl galactoglucomannan (GGM) for modification of NFC surface properties was studied. Four GGM-block-structured, amphiphilic derivatives were synthesized using either fatty acids or polydimethylsiloxane as hydrophobic tails. The adsorption of these GGM derivatives was consecutively examined in aqueous solution using a quartz crystal microbalance with dissipation monitoring (QCM-D). It was found that the hydrophobic tails did not hinder adsorption of the GGM derivatives to cellulose, which was concluded to be due to the presence of the native GGM-block with high affinity to cellulose. The layer properties of the adsorbed block-co-polymers were discussed and evaluated. Self-standing NFC films were further prepared and coated with the GGM derivatives and the effect of the surface modification on wetting properties and oxygen permeability (OP) of the modified films was assessed. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Structural modification in the formation of starch – silver nanocomposites

    International Nuclear Information System (INIS)

    Begum, S. N. Suraiya; Ramasamy, Radha Perumal; Aswal, V. K.

    2016-01-01

    Polymer based nanocomposites have gained wide applications in field of battery technology. Starch is a naturally occurring polysaccharide with sustainable properties such as biodegradable, non toxic, excellent film forming capacity and it also act as reducing agent for the metal nanoparticles. In our research various concentration of silver nitrate (AgNO 3 ) was added to the starch solution and films were obtained using solution casting method. Surface electron microscope (SEM) of the films shows modifications depending upon the concentration of AgNO 3 . Small angle neutron scattering (SANS) analysis showed that addition of silver nitrate modifies the starch to disc like structures and with increasing the AgNO 3 concentration leads to the formation of fractals. This research could benefit battery technology where solid polymer membranes using starch is used.

  6. Structural modification in the formation of starch – silver nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Begum, S. N. Suraiya; Ramasamy, Radha Perumal, E-mail: perumal.ramasamy@gmail.com [Department of Applied Science and Technology, A.C.Tech. Campus, Anna University, Chennai – 600 025 (India); Aswal, V. K. [Solid State Physics Division, Bhabha Atomic Research Center, Trombay, Mumbai (India)

    2016-05-23

    Polymer based nanocomposites have gained wide applications in field of battery technology. Starch is a naturally occurring polysaccharide with sustainable properties such as biodegradable, non toxic, excellent film forming capacity and it also act as reducing agent for the metal nanoparticles. In our research various concentration of silver nitrate (AgNO{sub 3}) was added to the starch solution and films were obtained using solution casting method. Surface electron microscope (SEM) of the films shows modifications depending upon the concentration of AgNO{sub 3}. Small angle neutron scattering (SANS) analysis showed that addition of silver nitrate modifies the starch to disc like structures and with increasing the AgNO{sub 3} concentration leads to the formation of fractals. This research could benefit battery technology where solid polymer membranes using starch is used.

  7. Structural modification in the formation of starch - silver nanocomposites

    Science.gov (United States)

    Begum, S. N. Suraiya; Aswal, V. K.; Ramasamy, Radha Perumal

    2016-05-01

    Polymer based nanocomposites have gained wide applications in field of battery technology. Starch is a naturally occurring polysaccharide with sustainable properties such as biodegradable, non toxic, excellent film forming capacity and it also act as reducing agent for the metal nanoparticles. In our research various concentration of silver nitrate (AgNO3) was added to the starch solution and films were obtained using solution casting method. Surface electron microscope (SEM) of the films shows modifications depending upon the concentration of AgNO3. Small angle neutron scattering (SANS) analysis showed that addition of silver nitrate modifies the starch to disc like structures and with increasing the AgNO3 concentration leads to the formation of fractals. This research could benefit battery technology where solid polymer membranes using starch is used.

  8. Ion-induced damage and amorphization in Si

    International Nuclear Information System (INIS)

    Holland, O.W.; White, C.W.

    1990-01-01

    Ion-induced damage growth in high-energy, self-ion irradiated Si was studied using electron microscopy and Rutherford backscattering spectroscopy. The results show that there is a marked variation in the rate of damage growth, as well as the damage morphology, along the path of the ion. Near the ion end-of-range (eor), damage increases monotonically with ion fluence until a buried amorphous layer is formed, while damage growth saturates at a low level in the region ahead. The morphology of the damage in the saturated region is shown to consist predominantly of simple defect clusters such as the divacancy. Damage growth remains saturated ahead of the eor until expansion of the buried amorphous layer encroaches into the region. A homogeneous growth model is presented which accounts for damage saturation, and accurately predicts the dose-rate dependence of the saturation level. Modifications of the model are discussed which are needed to account for the rapid growth in the eor region and near the interface of the buried amorphous layer. Two important factors contributing to rapid damage growth are identified. Spatial separation of the Frenkel defect pairs (i.e. interstitials and vacancies) due to the momentum of the interstitials is shown to greatly impact damage growth near the eor, while uniaxial strain in the interfacial region of the amorphous layer is identified as an important factor contributing to growth at that location. 20 refs., 10 figs

  9. Conformational impact of structural modifications in 2-fluorocyclohexanone

    Directory of Open Access Journals (Sweden)

    Francisco A. Martins

    2017-08-01

    Full Text Available 2-Haloketones are building blocks that combine physical, chemical and biological features of materials and bioactive compounds, while organic fluorine plays a fundamental role in the design of performance organic molecules. Since these features are dependent on the three-dimensional chemical structure of a molecule, simple structural modifications can affect its conformational stability and, consequently, the corresponding physicochemical/biological property of interest. In this work, structural changes in 2-fluorocyclohexanone were theoretically studied with the aim at finding intramolecular interactions that induce the conformational equilibrium towards the axial or equatorial conformer. The interactions evaluated were hydrogen bonding, hyperconjugation, electrostatic and steric effects. While the gauche effect, originated from hyperconjugative interactions, does not appear to cause some preferences for the axial conformation of organofluorine heterocycles, more classical effects indeed rule the conformational equilibrium of the compounds. Spectroscopic parameters (NMR chemical shifts and coupling constants, which can be useful to determine the stereochemistry and the interactions operating in the series of 2-fluorocyclohexanone derivatives, were also calculated.

  10. Cell and tissue structural modifications in hibernating dormice

    Directory of Open Access Journals (Sweden)

    Manuela Malatesta

    2005-06-01

    Full Text Available Abstract Tissues and cells of hibernating mammals undergo striking seasonal modifications of their activity through a quiescence-reactivation cycle. During winter, the temperature drastically decreases, the cell timing greatly slows down, the mitotic index sharply falls, DNA, RNA and protein synthesis are drastically reduced; however, upon arousal, all metabolic and physiological activities are quickly restored at the euthermic levels. The physiological, biochemical and behavioural aspects of hibernation have been extensively studied, but data on the morpho-functional relationships of cell and tissue components during the euthermia-hibernation-arousal cycle are rare. In this review, an overview of cell and tissue structural modifications so far reported in hibernating dormice is given and the possible role in the adaptation to the hypometabolic state as well as in the rapid resumption of activities upon arousal is discussed. Riassunto Modificazioni strutturali di cellule e tessuti in Gliridi ibernanti I tessuti e le cellule dei mammiferi ibernanti subiscono profonde modificazioni stagionali della loro attività attraverso un ciclo di quiescenza-riattivazione. Durante l'inverno, la temperatura corporea si abbassa a valori vicini a quelli ambientali, il ciclo cellulare rallenta, l'indice mitotico si riduce notevolmente e la sintesi di DNA, RNA e proteine è drasticamente ridotta. Tuttavia, al risveglio, tutte le attività metaboliche e fisiologiche sono rapidamente ristabilite ai livelli eutermici. Mentre gli aspetti fisiologici, biochimici e comportamentali dell'ibernazione sono stati ampiamenti studiati, i dati sulle relazioni morfo-funzionali dei componenti cellulari e tessutali durante il ciclo eutermia-ibernazione-risveglio sono piuttosto rari. In questo articolo vengono riassunte le attuali conoscenze sulle modificazioni strutturali di cellule e tessuti nei Gliridi ibernanti e viene discusso

  11. Structural Modification in Carbon Nanotubes by Boron Incorporation

    Directory of Open Access Journals (Sweden)

    Handuja Sangeeta

    2009-01-01

    Full Text Available Abstract We have synthesized boron-incorporated carbon nanotubes (CNTs by decomposition of ferrocene and xylene in a thermal chemical vapor deposition set up using boric acid as the boron source. Scanning and transmission electron microscopy studies of the synthesized CNT samples showed that there was deterioration in crystallinity and improvement in alignment of the CNTs as the boron content in precursor solution increased from 0% to 15%. Raman analysis of these samples showed a shift of ~7 cm−1in wave number to higher side and broadening of the G band with increasing boron concentration along with an increase in intensity of the G band. Furthermore, there was an increase in the intensity of the D band along with a decrease in its wave number position with increase in boron content. We speculate that these structural modifications in the morphology and microstructure of CNTs might be due to the charge transfer from boron to the graphite matrix, resulting in shortening of the carbon–carbon bonds.

  12. Advanced ion beam analysis of materials using ion-induced fast electron

    Energy Technology Data Exchange (ETDEWEB)

    Kudo, Hiroshi; Tanabe, Atsushi; Ishihara, Toyoyuki [Tsukuba Univ., Ibaraki (Japan)] [and others

    1997-03-01

    Recent progress in the study of high-energy shadowing effect using ion-induced electron spectroscopy is reported with emphasis on a possibility of determination of local electronic structure in solids, which has been a difficult problem to approach with other experimental techniques. We demonstrate real-space determination of covalent-bond electron distribution in Si crystal. The analysis technique may provide a new field of ion beam analysis of solids. (author)

  13. Structure modification of UHMWPE used for total joint replacements

    Czech Academy of Sciences Publication Activity Database

    Nevoralová, Martina; Baldrian, Josef; Pospíšil, Jan; Chodák, I.; Horák, Zdeněk

    74B, č. 2 (2005), s. 800-807 ISSN 1552-4973 R&D Projects: GA AV ČR IBS4050009 Institutional research plan: CEZ:AV0Z40500505 Keywords : UHMWPE * modification * gamma radiation Subject RIV: CD - Macromolecular Chemistry Impact factor: 1.621, year: 2005

  14. Heavy-ion-induced, gate-rupture in power MOSFETs

    International Nuclear Information System (INIS)

    Fischer, T.A.

    1987-01-01

    A new, heavy-ion-induced, burnout mechanism has been experimentally observed in power metal-oxide-semiconductor field-effect transistors (MOSFETs). This mechanism occurs when a heavy, charged particle passes through the gate oxide region of n- or p-channel devices having sufficient gate-to-source or gate-to-drain bias. The gate-rupture leads to significant permanent degradation of the device. A proposed failure mechanism is discussed and experimentally verified. In addition, the absolute immunity of p-channel devices to heavy-ion-induced, semiconductor burnout is demonstrated and discussed along with new, non-destructive, burnout testing methods

  15. Structural modifications under reactive atmosphere of cobalt catalysts; Modifications structurales sous atmospheres reactionnelles de catalyseurs a base de cobalt

    Energy Technology Data Exchange (ETDEWEB)

    Ducreux, O.

    1999-11-23

    The purpose of this work was to develop in situ methods under reactive dynamic conditions (XRD and Fourier transform infrared spectroscopy) to describe the active phase structure in order to understand Fischer-Tropsch catalyst behaviour and improve the natural gas conversion process performance. Experiments were designed to correlate structural modifications with catalytic results. The effect of ruthenium used as a promoter has also been studied. The impregnation process increases cobalt-support interaction. The presence of ruthenium promoter reduces this effect. Interactions between Co{sub 3}O{sub 4} oxide and support play an important role in the reducibility of cobalt and in the resulting metal structure. This in turn strongly influences the catalytic behaviour. Our results show a close correlation between structure modification and reactivity in the systems studied. Cobalt metal and CO can react to form a carbide Co{sub 2}C under conditions close to those of the Fischer-Tropsch synthesis. This carbide formation seems to be related to a deactivation process. The presence of interstitial carbon formed by dissociation of CO is proposed as a key to understanding the mechanism of the Fischer-Tropsch reaction. A specific catalyst activation treatment was developed to increase the catalytic activity. This work permits correlation of materials structure with their chemical properties and demonstrates the contribution of in situ physico-chemical characterisation methods to describe solids under reactive atmosphere. (author)

  16. New particle formation by ion-induced nucleation during dissipation ...

    Indian Academy of Sciences (India)

    ticle formation. Cluster ions can grow to form new particles and rate of such new particle forma- tion will be proportional to ion concentration or the ionization rate in the atmosphere (Dickinson. 1975). Later, many studies have identified ion- induced nucleation (IIN) as one of the most important source of atmospheric particles ...

  17. New particle formation by ion-induced nucleation during dissipation ...

    Indian Academy of Sciences (India)

    jess/120/05/0843-0850. Keywords. New particle formation; ion-induced nucleation; lightning intensity and rain. Abstract. A case of new particle formation observed during dissipation stage of a thunderstorm at a tropical station, Pune, India on 3 ...

  18. Structure modification design for bellow assembly of safety valve

    International Nuclear Information System (INIS)

    Zhou Yuan; Zheng Lanjiang; Zhang Donglin; Jiang Shenghan

    2010-01-01

    The welding and mechanical performance original welding structure of the bellow assembly of pilot operated safety valve was analyzed. The welding structure of the bellow assembly was modified with the Ω-ring. Both of the original and the new welding structure stress distribution were calculated with the method of thermal-structure multi-physics coupling. The result indicated that the compressive strength of the new structure can be improved. The qualification of welding procedure for the new structure has been down with the vacuum electron beam welding. The new assembly has passed the hydraulic pressure test. The reliability of the bellow assembly has been improved. (authors)

  19. [Lead compound optimization strategy (3)--Structure modification strategies for improving water solubility].

    Science.gov (United States)

    Li, Zeng; Wang, Jiang; Zhou, Yu; Liu, Hong

    2014-09-01

    Water solubility is an essential physical chemistry property of organic small molecule drug and is also a very important issue in drug discovery. Good water solubility often leads to a good drug potency and pleasant pharmacokinetic profiles. To improve water solubility, structure modification is a straight and effective way based on the theory of water solubility. This review summarized valid structure modification strategies for improving water solubility including salt formation, polar group introduction, liposolubility reduction, conformation optimization and prodrug.

  20. Moessbauer and positron annihilation studies of structural modifications of hemoglobin in solution

    International Nuclear Information System (INIS)

    Oshtrakh, M.I.; Kopelyan, E.A.; Semionkin, V.A.

    1995-01-01

    Structural modifications of human adult oxyhemoglobin in concentrated solution were studied by Moessbauer and positron life-time spectroscopies. The effects of non-sterile degradation and irradiation by γ-rays were compared by both techniques. It was found that positron annihilation parameters were sensitive to the structural modifications of hemoglobin molecules in solution and could be related with the conformational states of hemoglobin. (author)15 refs.; 3 tabs

  1. PTFE-nanocomposites structure and wear-resistance changing in various methods of structural modification

    Science.gov (United States)

    Mashkov, Yu K.; Ruban, A. S.; Rogachev, E. A.; Chemisenko, O. V.

    2018-01-01

    Conditions of polymer materials usage containing nanoelements as modifiers significantly affect the requirements for their physic-mechanical and tribological properties. However, the mechanisms of nanoparticles effect to the polymers tribotechnical properties have not been studied enough. The article aim is to analyze the results of studying polytetrafluoroethylene modified with cryptocrystalline graphite and silicon dioxide and to determine the effectiveness of the modification methods used and methods for further improving filled PTFE mechanical and tribotechnical properties. The effect of modifiers to PCM supramolecular structure was analyzed with SEM methods. The results of modifying the PCM samples surface by depositing a copper film with ion-vacuum deposition methods and changing the structural-phase composition and tribological characteristics are considered. The findings make possible to characterize the physicochemical processes under frictional interaction in metal polymer tribosystems.

  2. Strain-induced modification of magnetic structure and new magnetic ...

    Indian Academy of Sciences (India)

    of a metastable phase, i.e. to the growth of a film with a crystallographic structure different from the bulk one in normal temperature and pressure conditions. Both exchange and crystal field effects being very sensitive to the crystal structure, the ...... [15] M K Wilkinson, W C Koelher, E O Wollan and J W Cable, J. Appl. Phys.

  3. Investigations on structural disorder-induced modifications in the ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 39; Issue 4. Investigations on structural disorder-induced ... Structural studies using X-ray diffraction (XRD) measurements confirmed the single phasic nature of all the samples without any detectable impurities. The A-site size disorder ( σ 2 A) increased from 3.81 × 10 ...

  4. Maximum likelihood density modification by pattern recognition of structural motifs

    Science.gov (United States)

    Terwilliger, Thomas C.

    2004-04-13

    An electron density for a crystallographic structure having protein regions and solvent regions is improved by maximizing the log likelihood of a set of structures factors {F.sub.h } using a local log-likelihood function: (x)+p(.rho.(x).vertline.SOLV)p.sub.SOLV (x)+p(.rho.(x).vertline.H)p.sub.H (x)], where p.sub.PROT (x) is the probability that x is in the protein region, p(.rho.(x).vertline.PROT) is the conditional probability for .rho.(x) given that x is in the protein region, and p.sub.SOLV (x) and p(.rho.(x).vertline.SOLV) are the corresponding quantities for the solvent region, p.sub.H (x) refers to the probability that there is a structural motif at a known location, with a known orientation, in the vicinity of the point x; and p(.rho.(x).vertline.H) is the probability distribution for electron density at this point given that the structural motif actually is present. One appropriate structural motif is a helical structure within the crystallographic structure.

  5. Organic modification of glass structure : new glasses or new polymers?

    OpenAIRE

    Schmidt, Helmut K.

    1989-01-01

    The introduction of organic components into glass structures is possible by sol-gel techniques and leads to hybrid materials. The question whether these materials are more likely glasses or organic polymers is discussed. Different data show that the inorganic network structure governs important properties such as brittleness, hardness, or homogeneity. Other properties, such as density, free volume, or thermal stability depend on the organic groupings. Summarizing one can say that organically ...

  6. Structure modification of natural zeolite for waste removal application

    Science.gov (United States)

    Widayatno, W. B.

    2018-03-01

    Tremendous industrialization in the last century has led to the generation of huge amount of waste. One of the recent hot research topics is utilizing any advance materials and methods for waste removal. Natural zeolite as an inexpensive porous material with a high abundance holds a key for efficient waste removal owing to its high surface area. However, the microporous structure of natural zeolite hinders the adsorption of waste with a bigger molecular size. In addition, the recovery of natural zeolite after waste adsorption into its pores should also be considered for continuous utilization of this material. In this study, the porosity of natural zeolite from Tasikmalaya, Indonesia, was hydrothermally-modified in a Teflon-lined autoclave filled with certain pore directing agent such as distilled water, KOH, and NH4OH to obtain hierarchical pore structure. After proper drying process, the as-treated natural zeolite is impregnated with iron cation and heat-treated at specified temperature to get Fe-embedded zeolite structure. XRD observation is carried out to ensure the formation of magnetic phase within the zeolite pores. The analysis results show the formation of maghemite phase (γ-Fe2O3) within the zeolite pore structure.

  7. Swift heavy ion irradiation induced modification of structure and ...

    Indian Academy of Sciences (India)

    rovskite structure with space group R3c (Michel et al 1969). The unit cell parameters are a = 0·396 nm and α = 89◦. 28 (Blaauw and van der Woude 1973). Besides the robust multiferroic properties, BFO has been considered as a poten- tial candidate for enhancement of piezoelectric coefficients with doping (Fujino et al ...

  8. Structural modification of tantalum crystal induced by nitrogen ion ...

    Indian Academy of Sciences (India)

    resistance [28], chemical inertness and high mechanical hardness [29,30]. In this study, the results of nitrogen ion implantation into tantalum samples are discussed. The structural, composi- tional changes of modified surfaces as a function of ion dose are studied as well. The aim of this work is to find the optimum condition ...

  9. Ion-beam induced chemical and structural modification in polymers

    Czech Academy of Sciences Publication Activity Database

    Guenther, M.; Gerlach, G.; Suchaneck, G.; Sahre, K.; Eichorn, K. J.; Wolf, B.; Deineka, Alexander; Jastrabík, Lubomír

    158-159, - (2002), s. 108-113 ISSN 0257-8972 Grant - others:Ge(DE) 779/6-1 Institutional research plan: CEZ:AV0Z1010914 Keywords : polyimide * polyethersulfone- hardness * conductivity * polymer structure * ion implantation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.267, year: 2002

  10. Structural modification of tantalum crystal induced by nitrogen ion ...

    Indian Academy of Sciences (India)

    X-ray diffraction analysis (XRD) was applied for both the metallic Ta substrate and the study of new structures that have been created through the nitrogen ion implantation. Atomic force microscopy (AFM) was also used tocheck the roughness variations prior to and also after the implantation phase. The experimental results ...

  11. Structural modification of tantalum crystal induced by nitrogen ion ...

    Indian Academy of Sciences (India)

    Abstract. This paper investigates the effect of nitrogen ion implantation on tantalum surface structure. In this experiment, nitrogen ions which had an energy of 30 keV and doses of 1 × 10 17 to 10 × 10 17 ions cm − 2 were used. X-ray diffraction analysis (XRD) was applied for both the metallic Ta substrate and the study of ...

  12. Study of structural modification of PVA by incorporating Ag nanoparticles

    DEFF Research Database (Denmark)

    Saini, I.; Sharma, A.; Rozra, J.

    2016-01-01

    Nanocomposites of PVA with Ag nanoparticles dispersed in it were synthesized using solution casting method. The morphology and size distribution of Ag nanoparticles embedded in PVA matrix were obtained by transmission electron microscopy (TEM) and Field emission scanning electron microscopy (FE......-SEM). Raman spectroscopy was used to examine structural changes taking place inside polyvinyl alcohol (PVA) matrix due to incorporation of Ag nanoparticle. Raman analysis indicates that Ag nanoparticles interact with PVA through H-bonding. © 2016 Author(s)....

  13. Study of structural modification of PVA by incorporating Ag nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Saini, Isha; Sharma, Annu, E-mail: asharma@kuk.ac.in; Rozra, Jyoti; Aggarwal, Sanjeev [Department of Physics, Kurukshetra University, Kurukshetra 136119 (India); Dhiman, Rajnish [Department of Physics and Chemistry, University of Southern Denmark, Campusvej 55, DK-5230 Odense M (Denmark); Sharma, Pawan K. [Department of Chemistry, Kurukshetra University, Kurukshetra 136119 (India)

    2016-05-23

    Nanocomposites of PVA with Ag nanoparticles dispersed in it were synthesized using solution casting method. The morphology and size distribution of Ag nanoparticles embedded in PVA matrix were obtained by transmission electron microscopy (TEM) and Field emission scanning electron microscopy (FE-SEM). Raman spectroscopy was used to examine structural changes taking place inside polyvinyl alcohol (PVA) matrix due to incorporation of Ag nanoparticle. Raman analysis indicates that Ag nanoparticles interact with PVA through H-bonding.

  14. Structural modification of silica glass by laser scanning

    International Nuclear Information System (INIS)

    Zhao Jian; Sullivan, James; Zayac, John; Bennett, Ted D.

    2004-01-01

    The thermophysical nature of rapid CO 2 laser heating of silica glass is explored using a numerical simulation that considers the structural state of the glass, as characterized by the fictive temperature. The fictive temperature reflects the thermodynamic temperature at which the glass structure would be in equilibrium. To demonstrate that the thermophysical model can accurately predict the structural change in the glass, the fictive temperature is measured experimentally utilizing the fact that the fictive temperature change corresponds to a change of glass properties that can be revealed through wet chemical etching. The relationship between the etch rate and the fictive temperature is determined by preparing and etching samples of known fictive temperature. Wet chemical etching is used to measure the fictive temperature over the entire laser affected zone and the results are found to compare favorably with the results of the thermophysical model. The model and experimental measurements demonstrate that rapid laser processing results in an increased fictive temperature near the surface of the glass. The fictive temperature increase is about 1000 K and is uniform to within 5% over the laser affected zone. Near the boundary of this zone, the fictive temperature transitions abruptly to the value of the surrounding untreated glass

  15. Glycosphingolipid Modification: Structural Diversity, Functional and Mechanistic Integration of Diabetes

    Directory of Open Access Journals (Sweden)

    Tadashi Yamashita

    2011-08-01

    Full Text Available Glycosphingolipids (GSLs are present in all mammalian cell plasma membranes and intracellular membrane structures. They are especially concentrated in plasma membrane lipid domains that are specialized for cell signaling. Plasma membranes have typical structures called rafts and caveola domain structures, with large amounts of sphingolipids, cholesterol, and sphingomyelin. GSLs are usually observed in many organs ubiquitously. However, GSLs, including over 400 derivatives, participate in diverse cellular functions. Several studies indicate that GSLs might have an effect on signal transduction related to insulin receptors and epidermal growth factor receptors. GSLs may modulate immune responses by transmitting signals from the exterior to the interior of the cell. Guillain-Barré syndrome is one of the autoimmune disorders characterized by symmetrical weakness in the muscles of the legs. The targets of the immune response are thought to be gangliosides, which are one group of GSLs. Other GSLs may serve as second messengers in several signaling pathways that are important to cell survival or programmed cell death. In the search for clear evidence that GSLs may play critical roles in various biological functions, many researchers have made genetically engineered mice. Before the era of gene manipulation, spontaneous animal models or chemical-induced disease models were used.

  16. Thermally induced structural modification in the Al/Zr multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Qi; Zhang, Zhong; Ma, Shuang; Qi, Runze; Li, Jia [MOE Key Laboratory of Advanced Micro-Structured Materials, Institute of Precision Optical Engineering, Department of Physics, Tongji University, Shanghai 200092 (China); Wang, Zhanshan, E-mail: wangzs@tongji.edu.cn [MOE Key Laboratory of Advanced Micro-Structured Materials, Institute of Precision Optical Engineering, Department of Physics, Tongji University, Shanghai 200092 (China); Jonnard, Philippe; Le Guen, Karine; André, Jean-Michel [Laboratoire de Chimie Physique – Matière Rayonnement, UPMC Univ Paris 06, CNRS UMR 7614, 11 rue Pierre et Marie Curie, F-75231 Paris cedex 05 (France)

    2013-08-15

    The effect of increasing temperature on the structural stability and interactions of two kinds of Al/Zr (Al(1%wtSi)/Zr and Al(Pure)/Zr) multilayer mirrors are investigated. All Al/Zr multilayers annealed from 200 °C to 500 °C were deposited on Si wafers by using direct-current magnetron sputtering technology. A detailed and consistent picture of the thermally induced changes in the microstructure is obtained using an array of complementary measurements including grazing incidence X-ray reflectometry, atomic force microscopy, X-ray diffraction and high-resolution transmission electron microscopy. The first significant structural changes of two systems are observed at 250 °C, characterized by asymmetrical interlayers appearing at interface. At 290 °C, the interface consisting of amorphous Al–Zr alloy is transformed to amorphous Al–Zr alloy and cubic ZrAl{sub 3} in both systems. At 298 °C for Al(1%wtSi)/Zr and 295 °C for Al(Pure)/Zr multilayers, the interfacial phases of Al–Zr alloy transform into polycrystalline mixtures of hcp-ZrAl{sub 2} and cubic-ZrAl{sub 3}, which smooth the interface boundary and lower the surface roughness in the multilayers. Up to 500 °C, the multilayer structure still exists in both systems, and the differences between the asymmetrical interlayers are much larger in the multilayers. Finally, we discuss the transformation from symmetrical to asymmetrical in the annealing process for other multilayer systems.

  17. Modifications of the Mesoscopic Structure of Cellulose in Paper Degradation

    International Nuclear Information System (INIS)

    Missori, Mauro; Bicchieri, Marina; Mondelli, Claudia; De Spirito, Marco; Arcovito, Giuseppe; Papi, Massimiliano; Castellano, Carlo; Castellano, Agostina Congiu; Schweins, Ralf

    2006-01-01

    Paper is the main component of a huge quantity of cultural heritage. It is primarily composed of cellulose that undergoes significant degradation with the passage of time. By using small angle neutron scattering (SANS), we investigated cellulose's supramolecular structure, which allows access to degradation agents, in ancient and modern samples. For the first time, SANS data were interpreted in terms of water-filled pores, with their sizes increasing from 1.61 nm up to 1.97 nm in natural and artificially aged papers. The protective effect of gelatine sizing was also observed

  18. JEWEL predictions for Jet structure modifications at RHIC

    Science.gov (United States)

    Verma, Aditya; Kunnawalkam Elayavalli, Raghav; Salur, Sevil

    2017-09-01

    RHIC is ideally suited to investigate transport and tomographic properties of the quark gluon plasma in heavy ion collisions using fully reconstructed jets as hard probes. In this poster, we present predictions for inclusive di-jet and jet structure observables sensitive to jet-medium interactions. This is accomplished by harnessing JEWEL, a Monte Carlo event generator for heavy ion collisions with its updated medium recoil information. With JEWEL's successful record of predictions at the LHC, studying its performance at RHIC energies can precipitate an improved understanding of the jet quenching phenomena.

  19. YOGHURT STRUCTURE MODIFICATION WITH AMARANTH EXTRACT AND TRANGLUTAMINASE ADDITION

    Directory of Open Access Journals (Sweden)

    A. G. Shleikin

    2015-01-01

    Full Text Available To obtain functional dairy products is an important issue to improve the diet of the population. This article is devoted to development of yoghurt with transglutaminase enzyme. Transglutaminase (EC 2.3.2.13 performs cross-linking of proteins, strengthening the structure of the product. The concentration of transglutaminase used was 4 U/g of protein (0.1 %. Amaranth extract prepared from amaranth flour weighed in 5 % concentration per fermented samples volume was used as a vegetable additive to get yogurt. Yogurt was prepared a thermostately method. Milk was warmed up to 37 °C, amaranth extract and a transglutaminase was added. Study of samples of different compoundings is carried out. 1 – yogurt with amaranth extract (200 ml of milk + 100 ml of amaranth extract, 2 – the yogurt with amaranth extract prepared with adding of a transglutaminase (200 ml of milk + 100 ml of amaranth extract + 0.3 g of a transglutaminase and a control sample (300 ml of milk. Amaranth is composed of a variety of nutrients, valuable proteins, vitamins, squalene with antitumor activity. Influence of used additives on the fermented product structure and organoleptic properties was investigated. Results showed that durability of amaranth yogurt of high strength control for 6%, and durability of amaranth yogurt from the transglutaminase is 18% higher, than durability of the control. It was found consistence, viscosity and organoleptic properties had been improved.

  20. Effect of hydrothermal modification on the structure of REY zeolite studied by PAS

    International Nuclear Information System (INIS)

    Zhu Jun; Wang Shaojie

    2003-01-01

    The effect of temperature of the hydrothermal modification on the structure of Rare-earth Y zeolite (REY) was studied by positron annihilation spectroscopy. We measured the positron lifetime spectrum as a function of the temperature (300-800 degree C) of one hour hydrothermal modification for the REY zeolite after through pre-heated dehydration at 150 degree C. All lifetime spectra could be resolved into five components. The fifth lifetime component and its intensity were found to be related to the size and number of the secondary pores. The experimental results showed that the secondary pore in REY zeolite was produced by hydrothermal modification in some temperature range, and the largest size and the greatest quantity of the secondary pores were observed in the sample treated at 500 degree C for 1 hour. The effect of hydrothermal modification on REY zeolite without pre-heated dehydration was also discussed

  1. Cu nanoparticles induced structural, optical and electrical modification in PVA

    DEFF Research Database (Denmark)

    Rozra, J.; Saini, I.; Sharma, A.

    2012-01-01

    Cu nanoparticles were synthesized in PVA matrix by chemical reduction of cupric nitrate with hydrazine hydrate. Structural characterization of synthesized Cu-PVA nanocomposite was carried out using UV-Visible Spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission...... electron microscopy (TEM). Appearance of characteristic surface plasmon resonance peak of Cu nanoparticles at 591 nm in absorption spectra of Cu-PVA colloidal solution confirms the formation of Cu nanoparticles. TEM investigation indicates that Cu nanoparticles of size 16 nm are formed in PVA matrix which...... are in agreement with the size obtained using X-ray diffraction. Morphology of Cu-PVA nanocomposite was further confirmed using SEM. Analysis of UV-Visible absorption and reflection data indicates towards the reduction in optical band gap and increase in refractive index of the resulting nanocomposite...

  2. Ice cream structure modification by ice-binding proteins.

    Science.gov (United States)

    Kaleda, Aleksei; Tsanev, Robert; Klesment, Tiina; Vilu, Raivo; Laos, Katrin

    2018-04-25

    Ice-binding proteins (IBPs), also known as antifreeze proteins, were added to ice cream to investigate their effect on structure and texture. Ice recrystallization inhibition was assessed in the ice cream mixes using a novel accelerated microscope assay and the ice cream microstructure was studied using an ice crystal dispersion method. It was found that adding recombinantly produced fish type III IBPs at a concentration 3 mg·L -1 made ice cream hard and crystalline with improved shape preservation during melting. Ice creams made with IBPs (both from winter rye, and type III IBP) had aggregates of ice crystals that entrapped pockets of the ice cream mixture in a rigid network. Larger individual ice crystals and no entrapment in control ice creams was observed. Based on these results a model of ice crystals aggregates formation in the presence of IBPs was proposed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Structure modification of Mg-Nb films under hydrogen sorption cycles

    Energy Technology Data Exchange (ETDEWEB)

    Mengucci, P., E-mail: p.mengucci@univpm.it [Dipartimento di Fisica e Ingegneria dei Materiali e del Territorio, Universita Politecnica delle Marche, Via Brecce Bianche, I-60131 Ancona (Italy); Barucca, G.; Majni, G. [Dipartimento di Fisica e Ingegneria dei Materiali e del Territorio, Universita Politecnica delle Marche, Via Brecce Bianche, I-60131 Ancona (Italy); Bazzanella, N.; Checchetto, R.; Miotello, A. [Dipartimento di Fisica, Universita di Trento, Via Sommarive, I-38123 Povo (Italy)

    2011-09-15

    Research highlights: > Influence of Nb additions on the hydrogen kinetics of Mg layers. > Structure modification of the Mg matrix during hydrogen cycling. > Lattice strains induced by Nb tends to decrease during hydrogen cycling. > Nb nanoparticles form during hydrogen cycling. > Nb enhances the porous structure of the Mg layer formed during hydrogen cycling. - Abstract: In the present work we focus our attention on the structural modifications induced by repeated absorption/desorption cycles on Mg-Nb layers. Samples consisting of a 30 {mu}m thick pure Mg or Mg-5 at.% Nb doped films, coated with a 20 nm thick Pd layer were submitted to repeated H{sub 2} sorption cycles in a volumetric apparatus. Isothermal desorption analysis at 350 deg. C was performed to evaluate the amount of absorbed hydrogen. X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and electron microscopy techniques (SEM and TEM) were used for the structural characterisation of the samples. Analyses show a deep modification of the material upon cycling. The presence of Nb enhances the structural modifications and induces an initial lattice contraction of the Mg matrix that tends to decrease on cycling via the formation of Nb nanoparticles (with average size of {approx}10 nm). SEM and TEM observations performed in cross section evidenced the formation of a porous structure.

  4. Modification of C60/C70+Pd film structure under electric field influence during electron emission

    International Nuclear Information System (INIS)

    Czerwosz, E.; Dluzewski, P.; Kozlowski, M.

    2001-01-01

    We investigated the modification of structure of C 60 /C 70 +Pd films during cold electron emission from these films. Films were obtained by vacuum thermal deposition from two sources and were characterised before and after electron emission measurements by transmission electron microscopy and electron diffraction. Films were composed of nanocrystalline Pd objects dispersed in carbon/fullerenes matrix. I-V characteristics for electron emission were obtained in diode geometry with additionally applied voltage along the film surface. The modification of film structure occurred under applied electric field and the grouping of Pd nano crystals into bigger objects was observed

  5. Modification of LDPE molecular structure by gamma irradiation for bioapplications

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, L.M. [ITN, Nuclear and Technological Institute, EN 10, 2686-953 Sacavem (Portugal)]. E-mail: ferreira@itn.pt; Falcao, A.N. [ITN, Nuclear and Technological Institute, EN 10, 2686-953 Sacavem (Portugal); Gil, M.H. [Department of Chemical Engineering, Faculty of Science and Technology, University of Coimbra, Polo II - Pinhal de Marrocos, 3030-290 Coimbra (Portugal)

    2005-07-01

    The surface properties of low-density polyethylene (LDPE) can be modified by the grafting of 2-hydroxyethyl methacrylate (HEMA). This was done aiming at the production of new materials suitable for bioapplications. Samples with different monomer concentrations were prepared from LDPE particles by gamma irradiation, following different irradiation protocols, including irradiation in presence and absence of air. The samples were characterized by thermal analysis techniques (DSC and TGA) and by Fourier transform infrared spectroscopy (FTIR). The results obtained show a decrease in the crystallinity of the supporting matrix for copolymers with high yields of grafting. However, the new materials prepared maintain good structural order resulting from the protective effect of polyHEMA grafted onto LDPE backbone. These effects can improve the diffusion of other species deeper inside the matrix and increase the material hydrophilicity. The studies performed made possible the selection of experimental protocols adequate for the production of new copolymeric materials with high grafting yield. These were used in the production of new LDPE films with enhanced hydrophilic properties.

  6. Reduction and structural modification of zirconolite on He+ ion irradiation

    Science.gov (United States)

    Gupta, Merry; Kulriya, P. K.; Shukla, Rishabh; Dhaka, R. S.; Kumar, Raj; Ghumman, S. S.

    2016-07-01

    The immobilization of minor actinides and alkaline-earth metal is a major concern in nuclear industry due to their long-term radioactive contribution to the high level waste (HLW). Materials having zirconolite, pyrochlore, and perovskite structure are promising candidates for immobilization of HLW. The zirconolite which exhibits high radiation stability and corrosion resistance behavior is investigated for its radiation stability against alpha particles in the present study. CaZrTi2O7 pellets prepared using solid state reaction techniques, were irradiated with 30 keV He+ ions for the ion fluence varying from 1 × 1017 to 1 × 1021 ions/m2. Scanning electron microscopy (SEM) images of the un-irradiated sample exhibited well separated grains with average size of about 6.8 μm. On the ion irradiation, value of the average grains size was about 7.1 μm, and change in the microstructure was insignificant. The X-ray photoelectron spectroscopy (XPS) studies showed a shift in the core level peak position (of Ca 2p, Ti 2p and Zr 3d) towards lower binding energy with respect to pristine sample as well as loss of oxygen was also observed for sample irradiated with the ion fluence of 1 × 1020 ions/m2. These indicate a decrease in co-ordination number and the ionic character of Msbnd O bond. Moreover, core level XPS signal was not detected for sample irradiated with ion fluence of 1 × 1021 ions/m2, suggesting surface damage of the sample at this ion fluence. However, X-ray diffraction (XRD) studies showed that zirconolite was not amorphized even on irradiation up to a fluence order of 1 × 1021 ion/m2. But, significant decrease in peak intensity due to creation of defects and a marginal positive peak shift due to tensile strain induced by irradiation, were observed. Thus, XRD along with XPS investigation suggests that reduction, decrease in co-ordination number, and increase in covalency are responsible for the radiation damage in zirconolite.

  7. Effect of silver ion-induced disorder on morphological, chemical and optical properties of poly (methyl methacrylate)

    Energy Technology Data Exchange (ETDEWEB)

    Arif, Shafaq, E-mail: sarif2005@gmail.com [Department of Physics, Lahore College for Women University, Lahore 54000 (Pakistan); Saleemi, Farhat [Department of Physics, Lahore College for Women University, Lahore 54000 (Pakistan); Rafique, M. Shahid [Department of Physics, University of Engineering & Technology, Lahore 54000 (Pakistan); Naab, Fabian; Toader, Ovidiu [Department of Nuclear Engineering and Radiological Sciences, Michigan Ion Beam Laboratory, University of Michigan, MI 48109-2104 (United States); Mahmood, Arshad; Aziz, Uzma [National Institute of Lasers & Optronics (NILOP), P.O. Nilore, Islamabad (Pakistan)

    2016-11-15

    Ion implantation is a versatile technique to tailor the surface properties of polymers in a controlled manner. In the present study, samples of poly (methyl methacrylate) (PMMA) have been implanted with 400 keV silver (Ag{sup +}) ion beam to various ion fluences ranging from 5 × 10{sup 13} to 5 × 10{sup 15} ions/cm{sup 2}. The effect of Ag{sup +} ion-induced disorder on morphological, chemical and optical properties of PMMA is analyzed using Atomic Force Microscope (AFM), Fourier transform infrared spectroscopy (FTIR) and ultraviolet–visible (UV–Vis) spectroscopy. Furthermore, the electrical conductivity of pristine and implanted PMMA is measured using four probe apparatus. The AFM images revealed the growth of nano-sized grainy structures and hillocks above the surface of implanted PMMA. The FTIR spectra confirmed the modifications in chemical structure of PMMA along with the formation of −C=C− carbon contents. The refractive index, extinction coefficient and photoconductivity of implanted PMMA have been found to increase as a function of ion fluence. Simultaneously, indirect optical band gap is reduced from 3.13 to 0.81 eV at a relatively high fluence (5 × 10{sup 15} ions/cm{sup 2}). A linear correlation has been established between the band gap and Urbach energies. Moreover, the electrical conductivity of Ag{sup +} implanted PMMA has increased from 2.14 × 10{sup −10} (pristine) to 9.6 × 10{sup −6} S/cm.

  8. Evaluating response modification factor (R for some types of steel structure

    Directory of Open Access Journals (Sweden)

    Doralba Valencia Restrepo

    2008-01-01

    Full Text Available Response modification factor (R, tabulated in the Colombian Design Code as NSR-98, is used in this paper for eva-luating internal member forces produced by design earthquake action on steel structures and the inconsistencies pre-sent when designing structures when 1% drift limits must be complied with. The article presents the design of 45 frames corresponding to the seismic resistance system of 5 buildings: 15 special moment frames (SMF, 15 special concentrically-braced frames (CBF and 15 eccentrically-braced frames (EBF. External loads and their combination were used in estimating internal loads and rigidity demands (1% drift were evaluated in line with NSR-98 requi-rements. Member strength requirements were evaluated by using the AISC-2005 seismic provisions for steel structu-red buildings. Modal pushover analysis was used for evaluating the response modification factor for the 45 given frames at different structural performance levels. It was found that this factor was not constant for any of the three structural systems (SMF, CBF and EBF suggested by NSR-98 and that the values of the response modification factor found in the present investigation were smaller than those tabulated in this design code governing everyday structural design. This would lead to significant errors being made in evaluating design forces, not only in the structures but in the support elements (base-plates, foundations, shear walls and any structures attached to buildings constructed in line with the seismic resistance system.

  9. Characterization of Chromatin Structure-associated Histone Modifications in Breast Cancer Cells

    Directory of Open Access Journals (Sweden)

    Chang Pyo Hong

    2012-09-01

    Full Text Available Chromatin structure and dynamics that are influenced by epigenetic marks, such as histone modification and DNA methylation, play a crucial role in modulating gene transcription. To understand the relationship between histone modifications and regulatory elements in breast cancer cells, we compared our chromatin immunoprecipitation sequencing (ChIP-Seq histone modification patterns for histone H3K4me1, H3K4me3, H3K9/16ac, and H3K27me3 in MCF-7 cells with publicly available formaldehyde-assisted isolation of regulatory elements (FAIRE-chip signals in human chromosomes 8, 11, and 12, identified by a method called FAIRE. Active regulatory elements defined by FAIRE were highly associated with active histone modifications, like H3K4me3 and H3K9/16ac, especially near transcription start sites. The H3K9/16ac-enriched genes that overlapped with FAIRE signals (FAIRE-H3K9/14ac were moderately correlated with gene expression levels. We also identified functional sequence motifs at H3K4me1-enriched FAIRE sites upstream of putative promoters, suggesting that regulatory elements could be associated with H3K4me1 to be regarded as distal regulatory elements. Our results might provide an insight into epigenetic regulatory mechanisms explaining the association of histone modifications with open chromatin structure in breast cancer cells.

  10. Unique Structural Modifications Are Present in the Lipopolysaccharide from Colistin-Resistant Strains of Acinetobacter baumannii

    Science.gov (United States)

    2013-10-01

    SECURITY CLASSIFICATION OF: Acinetobacter baumannii is a nosocomial opportunistic pathogen that can cause severe infections, including hospital-acquired...distribution is unlimited. Unique Structural Modifications Are Present in the Lipopolysaccharide from Colistin-Resistant Strains of Acinetobacter baumannii ...from Colistin-Resistant Strains of Acinetobacter baumannii Report Title Acinetobacter baumannii is a nosocomial opportunistic pathogen that can cause

  11. Model Modification in Covariance Structure Modeling: A Comparison among Likelihood Ratio, Lagrange Multiplier, and Wald Tests.

    Science.gov (United States)

    Chou, Chih-Ping; Bentler, P. M.

    1990-01-01

    The empirical performance under null/alternative hypotheses of the likelihood ratio difference test (LRDT); Lagrange Multiplier test (evaluating the impact of model modification with a specific model); and Wald test (using a general model) were compared. The new tests for covariance structure analysis performed as well as did the LRDT. (RLC)

  12. Golgi structure formation, function, and post-translational modifications in mammalian cells.

    Science.gov (United States)

    Huang, Shijiao; Wang, Yanzhuang

    2017-01-01

    The Golgi apparatus is a central membrane organelle for trafficking and post-translational modifications of proteins and lipids in cells. In mammalian cells, it is organized in the form of stacks of tightly aligned flattened cisternae, and dozens of stacks are often linked laterally into a ribbon-like structure located in the perinuclear region of the cell. Proper Golgi functionality requires an intact architecture, yet Golgi structure is dynamically regulated during the cell cycle and under disease conditions. In this review, we summarize our current understanding of the relationship between Golgi structure formation, function, and regulation, with focus on how post-translational modifications including phosphorylation and ubiquitination regulate Golgi structure and on how Golgi unstacking affects its functions, in particular, protein trafficking, glycosylation, and sorting in mammalian cells.

  13. Optimization of ribosome structure and function by rRNA base modification.

    Directory of Open Access Journals (Sweden)

    Jennifer L Baxter-Roshek

    2007-01-01

    Full Text Available Translating mRNA sequences into functional proteins is a fundamental process necessary for the viability of organisms throughout all kingdoms of life. The ribosome carries out this process with a delicate balance between speed and accuracy. This work investigates how ribosome structure and function are affected by rRNA base modification. The prevailing view is that rRNA base modifications serve to fine tune ribosome structure and function.To test this hypothesis, yeast strains deficient in rRNA modifications in the ribosomal peptidyltransferase center were monitored for changes in and translational fidelity. These studies revealed allele-specific sensitivity to translational inhibitors, changes in reading frame maintenance, nonsense suppression and aa-tRNA selection. Ribosomes isolated from two mutants with the most pronounced phenotypic changes had increased affinities for aa-tRNA, and surprisingly, increased rates of peptidyltransfer as monitored by the puromycin assay. rRNA chemical analyses of one of these mutants identified structural changes in five specific bases associated with the ribosomal A-site.Together, the data suggest that modification of these bases fine tune the structure of the A-site region of the large subunit so as to assure correct positioning of critical rRNA bases involved in aa-tRNA accommodation into the PTC, of the eEF-1A.aa-tRNA.GTP ternary complex with the GTPase associated center, and of the aa-tRNA in the A-site. These findings represent a direct demonstration in support of the prevailing hypothesis that rRNA modifications serve to optimize rRNA structure for production of accurate and efficient ribosomes.

  14. Evaluating response modification factor (R) for some types of steel structure

    OpenAIRE

    Doralba Valencia Restrepo; Gabriel F. Valencia Clement

    2008-01-01

    Response modification factor (R), tabulated in the Colombian Design Code as NSR-98, is used in this paper for eva-luating internal member forces produced by design earthquake action on steel structures and the inconsistencies pre-sent when designing structures when 1% drift limits must be complied with. The article presents the design of 45 frames corresponding to the seismic resistance system of 5 buildings: 15 special moment frames (SMF), 15 special concentrically-braced frames (CBF) and 15...

  15. A vastly increased chemical variety of RNA modifications that includes a thioacetal structure.

    Science.gov (United States)

    Dal Magro, Christina; Keller, Patrick; Kotter, Annika; Werner, Stephan; Duarte, Victor; Marchand, Virginie; Ignarski, Michael; Freiwald, Anja; Müller, Roman-Ulrich; Dieterich, Christoph; Motorin, Yuri; Butter, Falk; Atta, Mohammed; Helm, Mark

    2018-04-06

    Recently discovered new chemical entities in RNA modifications have provided surprises with respect to functional groups that enlarge the chemical space of RNA. Using LC-MS, we found over one hundred signals of RNA constituents that contained a ribose moiety in tRNAs from E. coli. Feeding experiments with variegated stable isotope labeled compounds identified 37 compounds, representing new structures of RNA modifications. One structure was elucidated by deuterium exchange and high resolution mass spectrometry. The structure of msms2i6A (2-methylthiomethylenethio-N6-isopentenyl-adenosine) was confirmed by methione-D3 feeding experiments and finally by synthesis of the nucleobase. The msms2i6A contains a thioacetal, which we demonstrated in vitro to be biosynthetically derived from ms2i6A by the action of the radical-SAM enzyme MiaB. This enzyme performs thiomethylation, forming ms2i6A from i6A in a first turnover. The newly discovered thioacetal is formed by a second turnover, now involving hydrogen abstraction from the previously introduced methyl group. Not only are thioacetals extremely rare in natural product chemistry, but also does this constitute a novel enzymatic mechanism for their formation. In conjunction with the pool of 36 new modification, this work describes a new layer of RNA modification chemistry. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. MeV ion-induced strain at nanoisland-semiconductor surface and interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Ghatak, J. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Satpati, B. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Umananda, M. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India); Satyam, P.V. [Institute of Physics, Sachivalaya Marg, Bhubaneswar 751005 (India)]. E-mail: satyam@iopb.res.in; Akimoto, K. [Department of Quantum Engineering, Nagoya University, Nagoya 464-8603 (Japan); Ito, K. [Department of Quantum Engineering, Nagoya University, Nagoya 464-8603 (Japan); Emoto, T. [Toyota National College of Technology, 2-1, Toyota, Aichi 471-8525 (Japan)

    2006-03-15

    Strain at surfaces and interfaces play an important role in the optical and electronic properties of materials. MeV ion-induced strain determination in single crystal silicon substrates and in Ag (nanoisland)/Si(1 1 1) at surface/interfaces has been carried out using transmission electron microscopy (TEM) and surface-sensitive X-ray diffraction. Irradiation has been carried out with 1.5 MeV Au{sup 2+} ions at various fluences and impact angles. Selected area electron diffraction (SAED) and lattice imaging (using TEM) has been used to determine the strain at surface and interfaces. Preliminary results on the use of surface-sensitive asymmetric X-ray Bragg reflection method have been discussed. The TEM results directly indicate a contraction in the silicon lattice due to ion-induced effects. The nanoislands have shadowed the ion beam resulting in lesser strain beneath the island structures in silicon substrates. High-resolution lattice imaging has also been used to determine the strain in and around amorphization zones caused by the ion irradiation.

  17. Decay of Plutonium isotopes via spontaneous and heavy-ion induced fission paths

    Science.gov (United States)

    Sharma, Kanishka; Sawhney, Gudveen; Sharma, Manoj K.; Gupta, Raj K.

    2018-04-01

    Based on the collective clusterization approach, we have extended our earlier study on α-decay, exotic cluster-decay, and heavy particle radioactivity, to the phenomenon of spontaneous fission (SF) in the ground-state (g.s.) decays of even mass 234-246Pu parents. The calculations for the SF half-lives of these Pu-isotopes have been made within the framework of preformed cluster model (PCM), both for spherical as well as β2-deformed choices of shapes, and a comparison is made with the relevant available experimental data, which prefer spherical shapes. The importance of the orientation degree of freedom (hot compact or cold elongated configurations) is also explored. Next, in order to look for the exclusive role of heavy-ion induced fission, the dynamics of 6He + 238U reaction forming 244Pu* is studied over the center of mass energy range of E c . m . = 15.0- 28.8MeV, using the dynamical cluster-decay model (DCM), an extension of the PCM with temperature T- and angular momentum ℓ-effects included. The β2-deformed fragments of 244Pu* in the mass range A2 = 106- 113 (plus their complementary heavy fragments), corresponding to asymmetric fission peaks, are found contributing towards the fission cross-section. Finally, the potential energy surfaces and barrier modification effects are presented for the relative comparison of spontaneous and the heavy-ion induced fission processes. Both are found to behave similar with respect to the probable emission of fragments and hence point out to the shell closure property of the decay fragments.

  18. Plant Sterols: Chemical and Enzymatic Structural Modifications and Effects on Their Cholesterol-Lowering Activity.

    Science.gov (United States)

    He, Wen-Sen; Zhu, Hanyue; Chen, Zhen-Yu

    2018-03-28

    Plant sterols have attracted increasing attention due to their excellent cholesterol-lowering activity. However, free plant sterols have some characteristics of low oil solubility, water insolubility, high melting point, and low bioavailability, which greatly limit their application in foods. Numerous studies have been undertaken to modify their chemical structures to improve their chemical and physical properties in meeting the needs of various applications. The present review is to summarize the literature and update the progress on structural modifications of plant sterols in the following aspects: (i) synthesis of plant sterol esters by esterification and transesterification with hydrophobic fatty acids and triacylglycerols to improve their oil solubility, (ii) synthesis of plant sterol derivatives by coupling with various hydrophilic moieties to enhance their water solubility, and (iii) mechanisms by which plant sterols reduce plasma cholesterol and the effect of structural modifications on plasma cholesterol-lowering activity of plant sterols.

  19. Electronic excitation induced structural and optical modifications in InGaN/GaN quantum well structures grown by MOCVD

    Energy Technology Data Exchange (ETDEWEB)

    Prabakaran, K.; Ramesh, R.; Jayasakthi, M.; Surender, S.; Pradeep, S. [Crystal Growth Centre, Anna University, Chennai (India); Balaji, M. [National Centre for Nanoscience and Nanotechnology, University of Madras, Guindy Campus, Chennai (India); Asokan, K. [Inter-University Accelerator Centre, New Delhi (India); Baskar, K., E-mail: drbaskar2009@gmail.com [Crystal Growth Centre, Anna University, Chennai (India); Manonmaniam Sundaranar University, Tirunelveli (India)

    2017-03-01

    Highlights: • Effects on InGaN/GaN QW structures by Au{sup 7+} (100 MeV) ion have been investigated. • Structural defects of the irradiated InGaN/GaN QW structures are determined. • The intermixing effect in irradiated InGaN/GaN QW structures were understood. • Modified luminescence was observed in the PL spectra due to heavy ion irradiation. • Surface modification was observed due to the heavy ion irradiation. - Abstract: The present study focuses on the electronic excitation induced structural and optical properties of InGaN/GaN quantum well (QW) structures grown by metal organic chemical vapor deposition technique. These excitations were produced using Au{sup 7+} ion irradiation with 100 MeV energy. The X-ray rocking curves intensity and full width at half-maximum values corresponding to the planes of (0 0 0 2) and (1 0 −1 5) of the irradiated QW structures show the modifications in the screw and edge-type dislocation densities vary with the ion fluences. The structural characteristics using the reciprocal space mapping indicate the intermixing effects in InGaN/GaN QW structures. Atomic force microscopy images confirmed the presence of nanostructures and the surface modification due to heavy ion irradiation. The irradiated QW structures exhibited degraded photoluminescence intensity and a subsequent decrease in the yellow luminescence band intensity with the fluences of 1 × 10{sup 11} and 5 × 10{sup 12} ions/cm{sup 2} compared to the pristine QW structures.

  20. Structure-guided sequence specificity engineering of the modification-dependent restriction endonuclease LpnPI.

    Science.gov (United States)

    Sasnauskas, Giedrius; Zagorskaitė, Evelina; Kauneckaitė, Kotryna; Tamulaitiene, Giedre; Siksnys, Virginijus

    2015-07-13

    The eukaryotic Set and Ring Associated (SRA) domains and structurally similar DNA recognition domains of prokaryotic cytosine modification-dependent restriction endonucleases recognize methylated, hydroxymethylated or glucosylated cytosine in various sequence contexts. Here, we report the apo-structure of the N-terminal SRA-like domain of the cytosine modification-dependent restriction enzyme LpnPI that recognizes modified cytosine in the 5'-C(mC)DG-3' target sequence (where mC is 5-methylcytosine or 5-hydroxymethylcytosine and D = A/T/G). Structure-guided mutational analysis revealed LpnPI residues involved in base-specific interactions and demonstrated binding site plasticity that allowed limited target sequence degeneracy. Furthermore, modular exchange of the LpnPI specificity loops by structural equivalents of related enzymes AspBHI and SgrTI altered sequence specificity of LpnPI. Taken together, our results pave the way for specificity engineering of the cytosine modification-dependent restriction enzymes. © The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.

  1. Procedure for developing biological input for the design, location, or modification of water-intake structures

    Energy Technology Data Exchange (ETDEWEB)

    Neitzel, D.A.; McKenzie, D.H.

    1981-12-01

    To minimize adverse impact on aquatic ecosystems resulting from the operation of water intake structures, design engineers must have relevant information on the behavior, physiology and ecology of local fish and shellfish. Identification of stimulus/response relationships and the environmental factors that influence them is the first step in incorporating biological information in the design, location or modification of water intake structures. A procedure is presented in this document for providing biological input to engineers who are designing, locating or modifying a water intake structure. The authors discuss sources of stimuli at water intakes, historical approaches in assessing potential/actual impact and review biological information needed for intake design.

  2. MWW-type titanosilicate synthesis, structural modification and catalytic applications to green oxidations

    CERN Document Server

    Wu, Peng; Xu, Le; Liu, Yueming; He, Mingyuan

    2013-01-01

    This book provides a comprehensive review of a new generation of selective oxidation titanosilicate catalysts with the MWW topology (Ti-MWW) based on the research achievements of the past 12 years. It gives an overview of the synthesis, structure modification and catalytic properties of Ti-MWW. Ti-MWW can readily be prepared by means of direct hydrothermal synthesis with crystallization-supporting agents, using dual-structure-directing agents and a dry-gel conversion technique. It also can be post-synthesized through unique reversible structure transformation and liquid-phase isomorphous subst

  3. Probabilistic Structural Analysis of the Solid Rocket Booster Aft Skirt External Fitting Modification

    Science.gov (United States)

    Townsend, John S.; Peck, Jeff; Ayala, Samuel

    2000-01-01

    NASA has funded several major programs (the Probabilistic Structural Analysis Methods Project is an example) to develop probabilistic structural analysis methods and tools for engineers to apply in the design and assessment of aerospace hardware. A probabilistic finite element software code, known as Numerical Evaluation of Stochastic Structures Under Stress, is used to determine the reliability of a critical weld of the Space Shuttle solid rocket booster aft skirt. An external bracket modification to the aft skirt provides a comparison basis for examining the details of the probabilistic analysis and its contributions to the design process. Also, analysis findings are compared with measured Space Shuttle flight data.

  4. Structural and morphological modifications of polymer thin film in the presence of nonsolvent

    Energy Technology Data Exchange (ETDEWEB)

    Talukdar, Hrishikesh, E-mail: hiasst@yahoo.in; Kundu, Sarathi [Physical Sciences Division, Institute of Advanced Study in Science and Technology, Vigyan Path, Paschim Boragaon, Garchuk, Guwahati, Assam 781035 (India)

    2016-05-23

    Thin films of sodium poly(acrylic acid) salt (Na-PAA) have been investigated to obtain the modification of the out-of-plane structure and surface morphology in the presence of toluene which is considered as nonsolvent for Na-PAA. X-ray reflectivity analysis show that the out-of-plane thickness of the Na-PAA film increases if the film is kept for longer time inside the toluene. For the thicker film the effect of toluene is more pronounced than the thinner one. Surface morphology obtained from the atomic force microscopy shows that the top surface becomes relatively rough after the dipping of the Na-PAA film inside toluene. Although toluene is nonsolvent for Na-PAA molecules, however, the effect of restructuring of the nanometer-thick polymer film cannot be ignored. The reason for such structural modification has been proposed.

  5. Structural and morphological modifications of polymer thin film in the presence of nonsolvent

    Science.gov (United States)

    Talukdar, Hrishikesh; Kundu, Sarathi

    2016-05-01

    Thin films of sodium poly(acrylic acid) salt (Na-PAA) have been investigated to obtain the modification of the out-of-plane structure and surface morphology in the presence of toluene which is considered as nonsolvent for Na-PAA. X-ray reflectivity analysis show that the out-of-plane thickness of the Na-PAA film increases if the film is kept for longer time inside the toluene. For the thicker film the effect of toluene is more pronounced than the thinner one. Surface morphology obtained from the atomic force microscopy shows that the top surface becomes relatively rough after the dipping of the Na-PAA film inside toluene. Although toluene is nonsolvent for Na-PAA molecules, however, the effect of restructuring of the nanometer-thick polymer film cannot be ignored. The reason for such structural modification has been proposed.

  6. Stability and symmetry of ion-induced surface patterning

    Science.gov (United States)

    Matthes, Christopher S. R.; Ghoniem, Nasr M.; Walgraef, Daniel

    2017-12-01

    We present a continuum model of ion-induced surface patterning. The model incorporates the atomic processes of sputtering, re-deposition and surface diffusion, and is shown to display the generic features of the damped Kuramoto-Sivashinsky (KS) equation of non-linear dynamics. Linear and non-linear stability analyses of the evolution equation give estimates of the emerging pattern wavelength and spatial symmetry. The analytical theory is confirmed by numerical simulations of the evolution equation with the Fast Fourier Transform method, where we show the influence of the incident ion angle, flux, and substrate surface temperature. It is shown that large local geometry variations resulting in quadratic non-linearities in the evolution equation dominate pattern selection and stability at long time scales.

  7. Ion induced optical emission for surface and depth profile analysis

    International Nuclear Information System (INIS)

    White, C.W.

    1977-01-01

    Low-energy ion bombardment of solid surfaces results in the emission of infrared, visible, and ultraviolet radiation produced by inelastic ion-solid collision processes. The emitted optical radiation provides important insight into low-energy particle-solid interactions and provides the basis for an analysis technique which can be used for surface and depth profile analysis with high sensitivity. The different kinds of collision induced optical radiation emitted as a result of low-energy particle-solid collisions are reviewed. Line radiation arising from excited states of sputtered atoms or molecules is shown to provide the basis for surface and depth profile analysis. The spectral characteristics of this type of radiation are discussed and applications of the ion induced optical emission technique are presented. These applications include measurements of ion implant profiles, detection sensitivities for submonolayer quantities of impurities on elemental surfaces, and the detection of elemental impurities on complex organic substrates

  8. Electron and ion induced electron emission from metals and insulators

    CERN Document Server

    Steinbatz, M

    2001-01-01

    gradually exposed to oxygen as an experimental probe. The experimental data are fitted with an analytical model, that is able to describe the observed kinetics. The fit parameters give absolute values of sticking probabilities and of surface reaction rates. During oxidation of aluminum and magnesium also spontaneous emission of electrons (exoelectrons) is observed. This effect is quantitatively studied for different oxygen partial pressures. The experimental data also indicate a significant influence of the surface morphology on the exoemission process. An important consequence of atomic collisions in solids is ionization leading to electron ejection from the target atoms with subsequent migration through the solid. A certain fraction of these electrons finally reaches the surface and is ejected into vacuum. A standard measurement of this phenomenon is the observation of the particle (electron, ion) induced electron emission yield g, defined as the average number of ejected electrons per incoming projectile. ...

  9. Receptance based structural modification in a simple brake-clutch model for squeal noise suppression

    Science.gov (United States)

    Zarraga, Ondiz; Ulacia, Ibai; Abete, José Manuel; Ouyang, Huajiang

    2017-06-01

    Unlike brake squeal, brake-clutch squeal has rarely been studied, even though the cause of squeal noise is identical - dry friction acting at the contact interface. In this paper, a combined theoretical and experimental study is reported on squeal noise of a brake-clutch. On the theoretical side, a receptance-based inverse dynamic method is adopted to identify the mass or stiffness required to split the coupled modes of a brake-clutch model to achieve noise suppression. On the experimental side, the theoretically identified stiffness is implemented on the brake-clutch test rig in the form of a grounded spring and it is thus shown that the actual structural modification has removed the squeal noise. This is the first time that a theoretically derived structural modification is made on a brake-clutch model and shown to be able of completely suppressing actual squeal noise. This study establishes a way of suppressing friction-induced high-frequency noise through structural modification.

  10. Asymptomatic Independence and Separability in Convariance Structure Models: Implications for Specification Error, Power, and Model Modification.

    Science.gov (United States)

    Kaplan, D; Wenger, R N

    1993-10-01

    This article presents a didactic discussion on the role of asymptotically independent test statistics and separable hypotheses as they pertain to issues of specification error, power, and model modification in the covariance structure modeling framework. Specifically, it is shown that when restricting two parameter estimates on the basis of the multivariate Wald test, the condition of asymptotic independence is necessary but not sufficient for the univariate Wald test statistics to sum to the multivariate Wald test. Instead, what is required is mutual asymptotic independence (MAI) among the univariate tests. This result generalizes to sets of multivariate tests as well. When MA1 is lacking, hypotheses can exhibit transitive relationships. It is also shown that the pattern of zero and non-zero elements of the covariance matrix of the estimates are indicative of mutually asymptotically independent test statistics, separable and transitive hypotheses. The concepts of MAI, separability, and transitivity serve as an explanatory framework for how specification errors are propagated through systems of equations and how power analyses are differentially affected by specification errors of the same magnitude. A small population study supports the major findings of this article. The question of univariate versus multivariate sequential model modification is also addressed. We argue that multivariate sequential model modification strategies do not take into account the typical lack of MA1 thus inadvertently misleading substantive investigators. Instead, a prudent approach favors univariate sequential model modification.

  11. 200 MeV Ag+15 ion irradiation-induced modifications in structural, magnetic and dielectric properties of nanoparticles of Cu0.2Zn0.8Fe2O4 ferrite

    Science.gov (United States)

    Dolia, S. N.; Sharma, P. K.; Samariya, Arvind; Pareek, S. P.; Prasad, Arun S.; Dhawan, M. S.; Kumar, Sudhish; Asokan, K.

    2013-08-01

    The present investigation aims at studying the effect of swift heavy ion irradiation on the structural, magnetic and dielectric properties of the nanocrystalline Cu0.2Zn0.8Fe2O4 spinel ferrite. The sample was synthesised using the sol-gel technique and then irradiated with the 200 MeV Ag+15 ion beam. The Rietveld profile refinement of the X-ray diffraction patterns confirmed the cubic spinel structure of samples. The spherical morphology revealed through transmission electron microscopy images was consistent with the crystalline diameter. The overall magnetic behaviour pointed towards superparamagnetic relaxation at room temperature along with the significant increase in saturation magnetisation, coercivity and blocking temperature after irradiation. This could be attributed to the slight increase in the particle size and ion-induced modifications on the surface states of the nanoparticles. The enhancement in dielectric constant and loss tangent after irradiation could be attributed to the available Fe+2 ↔ Fe+3 and/or Zn+2 ↔ Zn+3 ion polarisation at the octahedral site, especially on grain boundaries of the sample.

  12. Investigation of orexin-2 selective receptor antagonists: Structural modifications resulting in dual orexin receptor antagonists.

    Science.gov (United States)

    Skudlarek, Jason W; DiMarco, Christina N; Babaoglu, Kerim; Roecker, Anthony J; Bruno, Joseph G; Pausch, Mark A; O'Brien, Julie A; Cabalu, Tamara D; Stevens, Joanne; Brunner, Joseph; Tannenbaum, Pamela L; Wuelfing, W Peter; Garson, Susan L; Fox, Steven V; Savitz, Alan T; Harrell, Charles M; Gotter, Anthony L; Winrow, Christopher J; Renger, John J; Kuduk, Scott D; Coleman, Paul J

    2017-03-15

    In an ongoing effort to explore the use of orexin receptor antagonists for the treatment of insomnia, dual orexin receptor antagonists (DORAs) were structurally modified, resulting in compounds selective for the OX 2 R subtype and culminating in the discovery of 23, a highly potent, OX 2 R-selective molecule that exhibited a promising in vivo profile. Further structural modification led to an unexpected restoration of OX 1 R antagonism. Herein, these changes are discussed and a rationale for selectivity based on computational modeling is proposed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Structural landscape of base pairs containing post-transcriptional modifications in RNA.

    Science.gov (United States)

    Seelam, Preethi P; Sharma, Purshotam; Mitra, Abhijit

    2017-06-01

    Base pairs involving post-transcriptionally modified nucleobases are believed to play important roles in a wide variety of functional RNAs. Here we present our attempts toward understanding the structural and functional role of naturally occurring modified base pairs using a combination of X-ray crystal structure database analysis, sequence analysis, and advanced quantum chemical methods. Our bioinformatics analysis reveals that despite their presence in all major secondary structural elements, modified base pairs are most prevalent in tRNA crystal structures and most commonly involve guanine or uridine modifications. Further, analysis of tRNA sequences reveals additional examples of modified base pairs at structurally conserved tRNA regions and highlights the conservation patterns of these base pairs in three domains of life. Comparison of structures and binding energies of modified base pairs with their unmodified counterparts, using quantum chemical methods, allowed us to classify the base modifications in terms of the nature of their electronic structure effects on base-pairing. Analysis of specific structural contexts of modified base pairs in RNA crystal structures revealed several interesting scenarios, including those at the tRNA:rRNA interface, antibiotic-binding sites on the ribosome, and the three-way junctions within tRNA. These scenarios, when analyzed in the context of available experimental data, allowed us to correlate the occurrence and strength of modified base pairs with their specific functional roles. Overall, our study highlights the structural importance of modified base pairs in RNA and points toward the need for greater appreciation of the role of modified bases and their interactions, in the context of many biological processes involving RNA. © 2017 Seelam et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.

  14. Structural modifications induced by ion irradiation and temperature in boron carbide B{sub 4}C

    Energy Technology Data Exchange (ETDEWEB)

    Victor, G., E-mail: g.victor@ipnl.in2p3.fr [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69622 Villeurbanne Cedex (France); Pipon, Y.; Bérerd, N. [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69622 Villeurbanne Cedex (France); Institut Universitaire de Technologie (IUT) Lyon-1, Université Claude Bernard Lyon 1, 69622 Villeurbanne Cedex (France); Toulhoat, N. [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69622 Villeurbanne Cedex (France); CEA-DEN, Saclay, 91191 Gif-sur-Yvette (France); Moncoffre, N. [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69622 Villeurbanne Cedex (France); Djourelov, N. [Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, 72 Tzarigradsko chaussee blvd, BG-1784 Sofia (Bulgaria); ELI-NP, IFIN-HH, 30 Reactorului Str, MG-6 Bucharest-Magurele (Romania); Miro, S. [CEA-DEN, Service de Recherches de Métallurgie Physique, Laboratoire JANNUS, F-91191 Gif-sur-Yvette (France); Baillet, J. [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69622 Villeurbanne Cedex (France); Pradeilles, N.; Rapaud, O.; Maître, A. [SPCTS, UMR CNRS 7315, Centre Européen de la céramique, University of Limoges (France); Gosset, D. [CEA, Saclay, DMN-SRMA-LA2M, 91191 Gif-sur-Yvette (France)

    2015-12-15

    Already used as neutron absorber in the current French nuclear reactors, boron carbide (B{sub 4}C) is also considered in the future Sodium Fast Reactors of the next generation (Gen IV). Due to severe irradiation conditions occurring in these reactors, it is of primary importance that this material presents a high structural resistance under irradiation, both in the ballistic and electronic damage regimes. Previous works have shown an important structural resistance of boron carbide even at high neutron fluences. Nevertheless, the structural modification mechanisms due to irradiation are not well understood. Therefore the aim of this paper is to study structural modifications induced in B{sub 4}C samples in different damage regimes. The boron carbide pellets were shaped and sintered by using spark plasma sintering method. They were then irradiated in several conditions at room temperature or 800 °C, either by favoring the creation of ballistic damage (between 1 and 3 dpa), or by favoring the electronic excitations using 100 MeV swift iodine ions (S{sub e} ≈ 15 keV/nm). Ex situ micro-Raman spectroscopy and Doppler broadening of annihilation radiation technique with variable energy slow positrons were coupled to follow the evolution of the B{sub 4}C structure under irradiation.

  15. Quantification of ion-induced molecular fragmentation of isolated 2-deoxy-D-ribose molecules

    NARCIS (Netherlands)

    Alvarado Chacon, F.; Bari, S.; Hoekstra, R.A.; Schlathölter, T.A.

    2006-01-01

    Recent experiments on low energy ion-induced damage to DNA building blocks indicate that ion induced DNA damage is dominated by deoxyribose disintegration (Phys. Rev. Lett., 2005, 95, 153201). We have studied interactions of keV H+ and Heq+ with isolated deoxyribose molecules by means of high

  16. Surface modification technique of structural ceramics: ion implantation-assisted multi-arc ion plating

    International Nuclear Information System (INIS)

    Peng Zhijian; Miao Hezhuo; Si Wenjie; Qi Longhao; Li Wenzhi

    2003-01-01

    Through reviewing the advantages and disadvantages of the existed surface modification techniques, a new technique, ion implantation-assisted multi-arc ion plating, was proposed. Using the proposed technique, the surfaces of silicon nitride ceramics were modified by Ti ion implantation, and then three kinds of ternary coatings, (Ti,Al)N, (Ti,Zr)N and (Ti,Cr)N, were deposited on the as-implanted ceramics. The coatings prepared by this technique are of high-hardness and well adhesive to the ceramic substrates. The maximal hardness measured by nanoindentation tests is more than 40 GPa. The maximal critical load by nanoscratch tests is more than 60 mN. The cutting tools prepared by this technique with the presented coatings are of excellent performance in industrial applications. The technique may be promising for the surface modification of structural ceramics. (orig.)

  17. Crystalline modifications and structural phase transitions of NaOH and NaOD

    International Nuclear Information System (INIS)

    Bleif, H.-J.; Dachs, H.

    1982-01-01

    Structural work on the three modifications of sodium hydroxide is reviewed. The monoclinic and cubic modifications were determined with neutron and X-ray diffraction, respectively. The phase-transition temperatures were determined by specific-heat measurements. The cubic to monoclinic transition is a first-order transition with a freezing of the rotational motion of the OH (and OD) groups. The monoclinic axes a, b and c* tend to be oriented parallel to the original cubic directions [-1-12], [1-10] and [111], respectively. The orthorhombic to monoclinic transition is a nearly continuous displacive phase transition with a soft acoustic shear mode. The order parameter is the homogeneous shear of the crystal in the a direction. Its temperature dependence is described within Landau theory. (Auth.)

  18. Iterative model-building, structure refinement, and density modification with the PHENIX AutoBuild Wizard

    Energy Technology Data Exchange (ETDEWEB)

    Los Alamos National Laboratory, Mailstop M888, Los Alamos, NM 87545, USA; Lawrence Berkeley National Laboratory, One Cyclotron Road, Building 64R0121, Berkeley, CA 94720, USA; Department of Haematology, University of Cambridge, Cambridge CB2 0XY, England; Terwilliger, Thomas; Terwilliger, T.C.; Grosse-Kunstleve, Ralf Wilhelm; Afonine, P.V.; Moriarty, N.W.; Zwart, P.H.; Hung, L.-W.; Read, R.J.; Adams, P.D.

    2007-04-29

    The PHENIX AutoBuild Wizard is a highly automated tool for iterative model-building, structure refinement and density modification using RESOLVE or TEXTAL model-building, RESOLVE statistical density modification, and phenix.refine structure refinement. Recent advances in the AutoBuild Wizard and phenix.refine include automated detection and application of NCS from models as they are built, extensive model completion algorithms, and automated solvent molecule picking. Model completion algorithms in the AutoBuild Wizard include loop-building, crossovers between chains in different models of a structure, and side-chain optimization. The AutoBuild Wizard has been applied to a set of 48 structures at resolutions ranging from 1.1 {angstrom} to 3.2 {angstrom}, resulting in a mean R-factor of 0.24 and a mean free R factor of 0.29. The R-factor of the final model is dependent on the quality of the starting electron density, and relatively independent of resolution.

  19. Iterative model building, structure refinement and density modification with the PHENIX AutoBuild wizard

    International Nuclear Information System (INIS)

    Terwilliger, Thomas C.; Grosse-Kunstleve, Ralf W.; Afonine, Pavel V.; Moriarty, Nigel W.; Zwart, Peter H.; Hung, Li-Wei; Read, Randy J.; Adams, Paul D.

    2008-01-01

    The highly automated PHENIX AutoBuild wizard is described. The procedure can be applied equally well to phases derived from isomorphous/anomalous and molecular-replacement methods. The PHENIX AutoBuild wizard is a highly automated tool for iterative model building, structure refinement and density modification using RESOLVE model building, RESOLVE statistical density modification and phenix.refine structure refinement. Recent advances in the AutoBuild wizard and phenix.refine include automated detection and application of NCS from models as they are built, extensive model-completion algorithms and automated solvent-molecule picking. Model-completion algorithms in the AutoBuild wizard include loop building, crossovers between chains in different models of a structure and side-chain optimization. The AutoBuild wizard has been applied to a set of 48 structures at resolutions ranging from 1.1 to 3.2 Å, resulting in a mean R factor of 0.24 and a mean free R factor of 0.29. The R factor of the final model is dependent on the quality of the starting electron density and is relatively independent of resolution

  20. BioJava-ModFinder: identification of protein modifications in 3D structures from the Protein Data Bank.

    Science.gov (United States)

    Gao, Jianjiong; Prlic, Andreas; Bi, Chunxiao; Bluhm, Wolfgang F; Dimitropoulos, Dimitris; Xu, Dong; Bourne, Philip E; Rose, Peter W

    2017-07-01

    We developed a new software tool, BioJava-ModFinder, for identifying protein modifications observed in 3D structures archived in the Protein Data Bank (PDB). Information on more than 400 types of protein modifications were collected and curated from annotations in PDB, RESID, and PSI-MOD. We divided these modifications into three categories: modified residues, attachment modifications, and cross-links. We have developed a systematic method to identify these modifications in 3D protein structures. We have integrated this package with the RCSB PDB web application and added protein modification annotations to the sequence diagram and structure display. By scanning all 3D structures in the PDB using BioJava-ModFinder, we identified more than 30 000 structures with protein modifications, which can be searched, browsed, and visualized on the RCSB PDB website. BioJava-ModFinder is available as open source (LGPL license) at ( https://github.com/biojava/biojava/tree/master/biojava-modfinder ). The RCSB PDB can be accessed at http://www.rcsb.org . pwrose@ucsd.edu. © The Author 2017. Published by Oxford University Press.

  1. Swift heavy ion induced modifications of single walled carbon nanotube thin films

    Energy Technology Data Exchange (ETDEWEB)

    Vishalli, E-mail: vishalli_2008@yahoo.com [Department of Physics, Panjab University, Chandigarh 160014 (India); Raina, K.K. [Materials Research Laboratory, School of Physics and Materials Science, Thapar University, P.O. Box 32, Patiala 147004, Punjab (India); Avasthi, D.K. [Materials Science Group, Inter University Accelerator Centre, Aruna Asaf Ali Marg, P.O. Box 10502, New Delhi 110067 (India); Srivastava, Alok [Department of Chemistry, Panjab University, Chandigarh 160014 (India); Dharamvir, Keya [Department of Physics, Panjab University, Chandigarh 160014 (India)

    2016-04-15

    Thin films of single walled carbon nanotubes (SWCNTs) were prepared by Langmuir–Blodgett method and irradiated with swift heavy ions, carbon and nickel each of energy 60 MeV. The ion beams have different electronic energy loss (S{sub e}) values and the samples were exposed to various irradiation doses. The irradiated films were characterized using Raman and optical absorption spectroscopy. Raman spectroscopy results indicate the competing processes of defect creation and healing (annealing) of SWCNTs at lower fluences, while at higher fluences defect creation or damage dominates. In UV–Vis–NIR spectroscopy we find that there is decrease in the intensity of characteristic peaks with every increasing fluence, indicating decrease in the optically active states with irradiation.

  2. Measurements of corona ion induced atmospheric electricity modification near to HV power lines

    Energy Technology Data Exchange (ETDEWEB)

    Matthews, J C; Buckley, A J; Keitch, P A; Wright, M D; Henshaw, D L [H H Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL (United Kingdom)], E-mail: J.C.Matthews@Bristol.ac.uk

    2008-12-01

    Corona ions emitted from high voltage power lines and propagated by the wind can attach at a given rate to atmospheric aerosols and will create disturbances in the Earth's DC electric field. Local electric field variations have been measured using field meters upwind and downwind of power lines and a fixed site monitoring station has been built to enable space charge near a power line to be continuously recorded. At similar sites, the high resolution mobility spectra of atmospheric ions and charged small aerosols have been ascertained using two custom-built mobility spectrometers. These measurement techniques have indicated an increase in the charge state of small aerosols at ground level and an increase in space charge with high variability downwind of high voltage power lines.

  3. Swift heavy ion induced modification in polycarbonate membrane for gas separation

    International Nuclear Information System (INIS)

    Rajesh Kumar; Prasad, Rajendra; Vijay, Y.K.; Das, D.

    2003-01-01

    Polymeric membranes are extensively used for commercial gas separation applications. Makrofol-KG (polycarbonate) is a glassy polymer. 40 μm thick sheet of Makrofol-KG was irradiated with 40 Ar (14.9 MeV/n) of fluence 10 3 ions/cm 2 and 20 μm thick sheet with 5.3 MeV α-particles of fluence 10 7 ions/cm 2 . The permeability of these polycarbonate membranes for H 2 and CO 2 was measured and also after etching in 6 N NaOH at 60 degC for different periods. Permeability is found to be increased with etching time. At a definite time, critical etching time, the permeability rapidly increases in PC. Positron annihilation lifetimes for unirradiated and irradiated membranes were measured with fast fast coincidence system to study the correlation of free volume hole concentration with gas separation properties. (author)

  4. Vocal Modification Abilities and Brain Structures in Parrots – how do they Correlate?

    DEFF Research Database (Denmark)

    Harpøth, Solveig Walløe

    .e. the oval nucleus of the mesopallium, MO and 3) investigate the effect of long-­term social and sound-isolation on the vocal modification ability and on the contact call of the peach-­fronted conure, Aratinga aurea. Article 1: The social complexity hypothesis states that with a complex social structure......Behavioral capability and related brain structures has been linked many times. It is a relationship that may vary between individuals and species, depending on for example the level of sociality. This PhD-­thesis investigates this relationship using parrots as experimental subjects. Parrots...... to have the least complex social structure and it was also the species that showed the least change to the contact call. The cockatiel and the peach-faced lovebird both show intermediary social complexity, and they also showed intermediary changes to their contact call, compared to the peach...

  5. High Hydrostatic Pressure (HHP-Induced Structural Modification of Patatin and Its Antioxidant Activities

    Directory of Open Access Journals (Sweden)

    Rizwan Elahi

    2017-03-01

    Full Text Available Patatin represents a group of homologous primary storage proteins (with molecular weights ranging from 40 kDa to 45 kDa found in Solanum tuberosum L. This group comprises 40% of the total soluble proteins in potato tubers. Here, patatin (40 kDa was extracted from potato fruit juice using ammonium sulfate precipitation (ASP and exposed to high hydrostatic pressure (HHP treatment (250, 350, 450, and 550 MPa. We investigated the effect of HHP treatment on the structure, composition, heat profile, and antioxidant potential, observing prominent changes in HHP-induced patatin secondary structure as compared with native patatin (NP. Additionally, significant (p < 0.05 increases in β-sheet content along with decreases in α-helix content were observed following HHP treatment. Thermal changes observed by differential scanning calorimetry (DSC also showed a similar trend following HHP treatment; however, the enthalpy of patatin was also negatively affected by pressurization, and free sulfhydryl content and surface hydrophobicity significantly increased with pressurization up to 450 MPa, although both interactions progressively decreased at 550 MPa. The observed physicochemical changes suggested conformational modifications in patatin induced by HHP treatment. Moreover, our results indicated marked enhancement of antioxidant potential, as well as iron chelation activities, in HHP-treated patatin as compared with NP. These results suggested that HHP treatment offers an effective and green process for inducing structural modifications and improving patatin functionality.

  6. Multicharged Ion-induced simple molecule fragmentation dynamics

    International Nuclear Information System (INIS)

    Tarisien, M.

    2003-10-01

    The aim of this work is to study the dynamics of swift multicharged ion-induced fragmentation of diatomic (CO) and triatomic (CO 2 ) molecules. Performed at the GANIL facility, this study used the Recoil Ion Momentum Spectroscopy technique (RIMS), which consists of a time-of-flight mass spectrometer, coupled with a multi-hit capability position sensitive detector (delay line anode). The high-resolution measurement of the kinetic energy distribution released (KER) during the CO fragmentation points out the limitation of the Coulomb Explosion Model, revealing, for example, the di-cation CO 2 + electronic state contribution in the case of C + /O + fragmentation pathway. Furthermore, the multi-ionization cross section dependence with the orientation of the internuclear axis of CO is compared with a geometrical model calculation. Finally, different behaviours are observed for the dissociation dynamics of a triatomic molecule (CO 2 ). While triple ionization leads mainly to a synchronous concerted fragmentation dynamics, a weak fraction of dissociating molecule follows a sequential dynamics involving CO 2 + metastable states. In the case of double ionization, (CO 2 ) 2+ di-cation dissociation dynamics is asynchronously concerted and has been interpreted using a simple model involving an asymmetrical vibration of the molecule. (author)

  7. Hydrogen ion induced ultralow wear of PEEK under extreme load

    Science.gov (United States)

    Yan, Shuai; Wang, Anying; Fei, Jixiong; Wang, Zhenyang; Zhang, Xiaofeng; Lin, Bin

    2018-03-01

    As a high-performance engineering polymer, poly(ether ether ketone) (PEEK) is a perfect candidate material for applications under extreme working conditions. However, its high wear rate greatly shortens its service life. In this study, ultralow friction and wear between PEEK and silicon nitride (Si3N4) under extreme-load conditions (with a mean contact pressure above 100 MPa) are found in acid lubricating solutions. Both friction and wear decrease sharply with decreasing pH. At pH = 1, the friction coefficient decreases by an order of magnitude and the wear rate of the PEEK decreases by two orders of magnitude compared to the results with water lubrication. These reductions in friction and wear occur for different speed, load, and surface roughness conditions. The underlying mechanism can be attributed to the formation of hydrogen-ion-induced electrical double layers on the surfaces of PEEK and Si3N4. The combined effect of the resulting repulsive force, electro-viscosity, and low shear strength of the water layer dramatically reduces both friction and wear.

  8. Heavy-ion induced genetic changes and evolution processes

    Science.gov (United States)

    Yang, C. H.; Craise, L. M.; Durante, M.; Mei, M.

    1994-01-01

    On Moon and Mars, there will be more galactic cosmic rays and higher radiation doses than on Earth. Our experimental studies showed that heavy ion radiation can effectively cause mutation and chromosome aberrations and that high Linear Energy Transfer (LET) heavy-ion induced mutants can be irreversible. Chromosome translocations and deletions are common in cells irradiated by heavy particles, and ionizing radiations are effective in causing hyperploidy. The importance of the genetic changes in the evolution of life is an interesting question. Through evolution, there is an increase of DNA content in cells from lower forms of life to higher organisms. The DNA content, however, reached a plateau in vertebrates. By increasing DNA content, there can be an increase of information in the cell. For a given DNA content, the quality of information can be changed by rearranging the DNA. Because radiation can cause hyperploidy, an increase of DNA content in cells, and can induce DNA rearrangement, it is likely that the evolution of life on Mars will be effected by its radiation environment. A simple analysis shows that the radiation level on Mars may cause a mutation frequency comparable to that of the spontaneous mutation rate on Earth. To the extent that mutation plays a role in adaptation, radiation alone on Mars may thus provide sufficient mutation for the evolution of life.

  9. Probabilistic Structural Analysis of the SRB Aft Skirt External Fitting Modification

    Science.gov (United States)

    Townsend, John S.; Peck, J.; Ayala, S.

    1999-01-01

    NASA has funded several major programs (the PSAM Project is an example) to develop Probabilistic Structural Analysis Methods and tools for engineers to apply in the design and assessment of aerospace hardware. A probabilistic finite element design tool, known as NESSUS, is used to determine the reliability of the Space Shuttle Solid Rocket Booster (SRB) aft skirt critical weld. An external bracket modification to the aft skirt provides a comparison basis for examining the details of the probabilistic analysis and its contributions to the design process.

  10. Enhanced osteointegration of medical titanium implant with surface modifications in micro/nanoscale structures

    Directory of Open Access Journals (Sweden)

    Liwen Lin

    2014-01-01

    Full Text Available Biomimetic design and substrate-based surface modification of medical implants will help to improve the integration of tissue to its material interfaces. Surface energy, composition, roughness, and topography all influence the biological responses of the implants, such as protein adsorption and cell adhesion, proliferation and differentiation. In the current study, different surface structures of Ti implants were constructed using facile surface techniques to create various micro-, nano-, and nano/micro composite scale topography. We have fabricated three types of hierarchical structures of TiO2 coating on Ti implants, including nanotube structure, nano sponge-like structure, and nano/micro nest-like structure. The osteointegration and biomechanical performance of the coated Ti screws were evaluated by histology and removal of torque force test in vivo. We found that the nano/micro nest-like and nanotube structured surface possessed better osteointegration ability. It indicated that the alkaline hydrothermally treated Ti substrate was the best for bone-implant integration in terms of all in vitro and in vivo testing parameters. The alkaline hydrothermally treated surface displayed a hydrophilic (contact angle value 5.92 ± 1.2, higher roughness (Ra value 911.3 ± 33.8 nm, higher specific surface area (8.26 ± 1.051 m2/g, and greater apatite inductivity. The electrochemical surface modification may become a powerful approach to enhance metal implant to bone integration in orthopaedic applications.

  11. Crystal structure of a PCP/Sfp complex reveals the structural basis for carrier protein posttranslational modification.

    Science.gov (United States)

    Tufar, Peter; Rahighi, Simin; Kraas, Femke I; Kirchner, Donata K; Löhr, Frank; Henrich, Erik; Köpke, Jürgen; Dikic, Ivan; Güntert, Peter; Marahiel, Mohamed A; Dötsch, Volker

    2014-04-24

    Phosphopantetheine transferases represent a class of enzymes found throughout all forms of life. From a structural point of view, they are subdivided into three groups, with transferases from group II being the most widespread. They are required for the posttranslational modification of carrier proteins involved in diverse metabolic pathways. We determined the crystal structure of the group II phosphopantetheine transferase Sfp from Bacillus in complex with a substrate carrier protein in the presence of coenzyme A and magnesium, and observed two protein-protein interaction sites. Mutational analysis showed that only the hydrophobic contacts between the carrier protein's second helix and the C-terminal domain of Sfp are essential for their productive interaction. Comparison with a similar structure of a complex of human proteins suggests that the mode of interaction is highly conserved in all domains of life. Copyright © 2014 Elsevier Ltd. All rights reserved.

  12. Structural insights into DNA sequence recognition by Type ISP restriction-modification enzymes.

    Science.gov (United States)

    Kulkarni, Manasi; Nirwan, Neha; van Aelst, Kara; Szczelkun, Mark D; Saikrishnan, Kayarat

    2016-05-19

    Engineering restriction enzymes with new sequence specificity has been an unaccomplished challenge, presumably because of the complexity of target recognition. Here we report detailed analyses of target recognition by Type ISP restriction-modification enzymes. We determined the structure of the Type ISP enzyme LlaGI bound to its target and compared it with the previously reported structure of a close homologue that binds to a distinct target, LlaBIII. The comparison revealed that, although the two enzymes use almost a similar set of structural elements for target recognition, the residues that read the bases vary. Change in specificity resulted not only from appropriate substitution of amino acids that contacted the bases but also from new contacts made by positionally distinct residues directly or through a water bridge. Sequence analyses of 552 Type ISP enzymes showed that the structural elements involved in target recognition of LlaGI and LlaBIII were structurally well-conserved but sequentially less-conserved. In addition, the residue positions within these structural elements were under strong evolutionary constraint, highlighting the functional importance of these regions. The comparative study helped decipher a partial consensus code for target recognition by Type ISP enzymes. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

  13. STRUCTURAL MODIFICATION OF NEW FORMATIONS IN CEMENT MATRIX USING CARBON NANOTUBE DISPERSIONS AND NANOSILICA

    Directory of Open Access Journals (Sweden)

    B. M. Khroustalev

    2017-01-01

    Full Text Available Complex nanodispersed systems with multi-walled carbon nanotubes and nanodispersed silica have a significant impact on the processes of hydration, hardening and strength gain of construction composites predetermining their durability. While using a scanning electron microscope with an attachment for X-ray microanalysis and a device for infrared spectral analysis investigations have shown that the main effect of the cement matrix modification in the case of adding complex nanodispersed systems is provided by direct influence of hydration processes with subsequent crystallization of new formations. It has been noted that while adding carbon nanotube dispersion and nanosized silica a binding matrix is structured in the form of an extremely dense shell from crystalline hydrate new formations on the surface of solid phases that provides strong binding matrix in cement concrete. The addition effect of carbon nanotubes has been analyzed and quantitatively assessed through an investigation for every case of one sample with nanotubes and one sample without them with the help of a nanoindenter and scanning electron microscope. It is necessary to solve rather complicated challenging task in order to assess quantitatively the addition effect of CNT on material characteristics at a micromechanical level. At the same time it is possible to investigate surface of a concrete sample with one-micron resolution. In this case it is necessary to prepare samples for nanoindentation with exclusion of all CNT defectable effects that have been shown by a SEM. So in this case more adequate method for assessment must be a picoindenter , which combines a test method for nanoindentation with an optical SEM potential. Such equipment is in the stage of in-situ testing process at the Vienna University of Technology. The investigation is based on the fact that the main modification effect of mineral binding matrix while using incorporated complex nanodispersed systems and

  14. Finite element analysis for structural modification and control resonance of a vertical pump

    Directory of Open Access Journals (Sweden)

    Dalia M. El-Gazzar

    2017-12-01

    Full Text Available The main objective of this research was to evaluate and enhance dynamic performance for a vertical pumping unit. The original electric motor of the pump unit had been replaced by another one different in design and weights. Vibration has been increased greatly after installing the new motor. Consequently, it is necessary to estimate the change in the vibration characteristics owing to the difference in the boundary conditions of the new motor. Measured vibration levels and frequency analysis were dangerous at 1× due to resonance problem. Finite Element Analysis was used to model the motor structure in order to find its natural frequencies and mode shapes. The results confirm that the third natural frequency is very close to 1× operating speed with deviation about 1%. To solve the resonance problem, it was recommended to increase the structure stiffness. The results after modifications confirmed that the overall vibration level decreases by 89%. Keywords: Vibration, Vertical pump, Modal analysis

  15. Concerted Flexibility of Chromatin Structure, Methylome, and Histone Modifications along with Plant Stress Responses

    Directory of Open Access Journals (Sweden)

    Ana Paula Santos

    2017-01-01

    Full Text Available The spatial organization of chromosome structure within the interphase nucleus, as well as the patterns of methylome and histone modifications, represent intersecting layers that influence genome accessibility and function. This review is focused on the plastic nature of chromatin structure and epigenetic marks in association to stress situations. The use of chemical compounds (epigenetic drugs or T-DNA-mediated mutagenesis affecting epigenetic regulators (epi-mutants are discussed as being important tools for studying the impact of deregulated epigenetic backgrounds on gene function and phenotype. The inheritability of epigenetic marks and chromatin configurations along successive generations are interpreted as a way for plants to “communicate” past experiences of stress sensing. A mechanistic understanding of chromatin and epigenetics plasticity in plant response to stress, including tissue- and genotype-specific epigenetic patterns, may help to reveal the epigenetics contributions for genome and phenotype regulation.

  16. Probing the Subtle Structure Modifications of Thermoelectric Materials by Variable Temperature Total Scattering

    DEFF Research Database (Denmark)

    Reardon, Hazel; Iversen, Bo Brummerstedt; Blichfeld, Anders Bank

    in air. PDF measurements were performed on data collected from ex situ annealed BGG samples. This ex situ study (to be submitted), reveals that the seemingly subtle change in the clathrate structure and the emergence of a significant amorphous phase observed from PXRD data is likely to be the result...... of modifications in the cage configuration, but further data analysis is necessary to identify the specific features of the cages that are affected. Although the thermal stability of thermoelectric materials has been highlighted as a critical bottleneck in their commercialization, the aim of this work...... is to understand how we may stabilize TE materials through a thorough understanding of their high temperature structure reorientations and decomposition mechanisms....

  17. Structural modification of herboxidiene by substrate-flexible cytochrome P450 and glycosyltransferase.

    Science.gov (United States)

    Jha, Amit Kumar; Dhakal, Dipesh; Van, Pham Thi Thuy; Pokhrel, Anaya Raj; Yamaguchi, Tokutaro; Jung, Hye Jin; Yoon, Yeo Joon; Sohng, Jae Kyung

    2015-04-01

    Herboxidiene is a natural product produced by Streptomyces chromofuscus exhibiting herbicidal activity as well as antitumor properties. Using different substrate-flexible cytochrome P450s and glycosyltransferase, different novel derivatives of herboxidiene were generated with structural modifications by hydroxylation or epoxidation or conjugation with a glucose moiety. Moreover, two isomers of herboxidiene containing extra tetrahydrofuran or tetrahydropyran moiety in addition to the existing tetrahydropyran moiety were characterized. The hydroxylated products for both of these compounds were also isolated and characterized from S. chromofuscus PikC harboring pikC from the pikromycin gene cluster of Streptomyces venezuelae and S. chromofuscus EryF harboring eryF from the erythromycin gene cluster of Saccharopolyspora erythraea. The compounds generated were characterized by high-resolution quadrupole-time-of-flight electrospray ionization mass spectrometry (HR-QTOF-ESI/MS) and (1)H- and (13)C-nuclear magnetic resonance (NMR) analyses. The evaluation of antibacterial activity against three Gram-positive bacteria, Micrococcus luteus, Bacillus subtilis, and Staphylococcus aureus, indicated that modification resulted in a transition from anticancer to antibacterial potency.

  18. The Use of Gene Modification and Advanced Molecular Structure Analyses towards Improving Alfalfa Forage

    Energy Technology Data Exchange (ETDEWEB)

    Lei, Yaogeng; Hannoufa, Abdelali; Yu, Peiqiang

    2017-01-29

    Alfalfa is one of the most important legume forage crops in the world. In spite of its agronomic and nutritive advantages, alfalfa has some limitations in the usage of pasture forage and hay supplement. High rapid degradation of protein in alfalfa poses a risk of rumen bloat to ruminants which could cause huge economic losses for farmers. Coupled with the relatively high lignin content, which impedes the degradation of carbohydrate in rumen, alfalfa has unbalanced and asynchronous degradation ratio of nitrogen to carbohydrate (N/CHO) in rumen. Genetic engineering approaches have been used to manipulate the expression of genes involved in important metabolic pathways for the purpose of improving the nutritive value, forage yield, and the ability to resist abiotic stress. Such gene modification could bring molecular structural changes in alfalfa that are detectable by advanced structural analytical techniques. These structural analyses have been employed in assessing alfalfa forage characteristics, allowing for rapid, convenient and cost-effective analysis of alfalfa forage quality. In this article, we review two major obstacles facing alfalfa utilization, namely poor protein utilization and relatively high lignin content, and highlight genetic studies that were performed to overcome these drawbacks, as well as to introduce other improvements to alfalfa quality. We also review the use of advanced molecular structural analysis in the assessment of alfalfa forage for its potential usage in quality selection in alfalfa breeding.

  19. Modification and structuring of conducting polymer films on insulating substrates by ion beam treatment

    International Nuclear Information System (INIS)

    Asmus, T.; Wolf, Gerhard K.

    2000-01-01

    Besides the commonly used procedures of UV-, X-ray and electron beam lithography, surface structuring by ion beam processes represents an alternative route to receive patterns in the nanometre-micrometre scale. In this work we focused on changes of surface properties of the polymer materials induced by ion irradiation and on reproducing hexagonal and square patterns in the micrometre scale. To achieve a better understanding of modification and structuring of insulating and conducting polymers by ion beam treatment we investigated effects of 14 keV Ar + bombardment on thin films of doped conducting polyethoxithiophene (PEOT) and polyethylenedioxithiophene (PEDT) on polyethersulfone (PES) as insulating substrate within the fluence range from 10 14 to 10 17 ions/cm 2 . Changes of surface properties like wettability, solubility, topology and electrochemical behaviour have been studied by contact angle technique, AFM/LFM, cyclovoltammetry and electrochemical microelectrode. By irradiation through copper masks structured patterns were achieved. These patterns can be converted by galvanic or electroless copper deposition in structured metal layers

  20. A graph modification approach for finding core-periphery structures in protein interaction networks.

    Science.gov (United States)

    Bruckner, Sharon; Hüffner, Falk; Komusiewicz, Christian

    2015-01-01

    The core-periphery model for protein interaction (PPI) networks assumes that protein complexes in these networks consist of a dense core and a possibly sparse periphery that is adjacent to vertices in the core of the complex. In this work, we aim at uncovering a global core-periphery structure for a given PPI network. We propose two exact graph-theoretic formulations for this task, which aim to fit the input network to a hypothetical ground truth network by a minimum number of edge modifications. In one model each cluster has its own periphery, and in the other the periphery is shared. We first analyze both models from a theoretical point of view, showing their NP-hardness. Then, we devise efficient exact and heuristic algorithms for both models and finally perform an evaluation on subnetworks of the S. cerevisiae PPI network.

  1. Surface structure modification of single crystal graphite after slow, highly charged ion irradiation

    Science.gov (United States)

    Alzaher, I.; Akcöltekin, S.; Ban-d'Etat, B.; Manil, B.; Dey, K. R.; Been, T.; Boduch, P.; Rothard, H.; Schleberger, M.; Lebius, H.

    2018-04-01

    Single crystal graphite was irradiated by slow, highly charged ions. The modification of the surface structure was studied by means of Low-Energy Electron Diffraction. The observed damage cross section increases with the potential energy, i.e. the charge state of the incident ion, at a constant kinetic energy. The potential energy is more efficient for the damage production than the kinetic energy by more than a factor of twenty. Comparison with earlier results hints to a strong link between early electron creation and later target atom rearrangement. With increasing ion fluence, the initially large-scale single crystal is first transformed into μ m-sized crystals, before complete amorphisation takes place.

  2. Modifications in interaction and structure of silica nanoparticle-BSA protein system in aqueous electrolyte solution

    Science.gov (United States)

    Yadav, Indresh; Aswal, V. K.; Kohlbrecher, J.

    2015-06-01

    SANS measurements have been carried out to examine the modifications in interaction and structure of anionic silica nanoparticle with anionic BSA protein in presence of an electrolyte. The phase behaviour of anionic silica nanoparticle and anionic BSA protein is governed by the protein induced depletion interaction between nanoparticles. Both nanoparticle and protein coexist individually at low protein concentrations as electrostatic repulsion dominates over the depletion interaction. However, depletion induced fractal aggregates of nanoparticles are formed at higher protein concentrations. These aggregates can be formed at much smaller protein concentration in presence of an electrolyte. We show that both the electrostatic (decrease) and depletion interaction (increase) are modified with an electrolyte. The range of the depletion interaction is found to be significantly larger than the electrostatic interaction.

  3. Structural modifications of bacterial lipopolysaccharide that facilitate Gram-negative bacteria evasion of host innate immunity

    Directory of Open Access Journals (Sweden)

    Motohiro eMatsuura

    2013-05-01

    Full Text Available Bacterial lipopolysaccharide (LPS, a cell wall component characteristic of Gram-negative bacteria, is a representative pathogen-associated molecular pattern that allows mammalian cells to recognize bacterial invasion and trigger innate immune responses. The polysaccharide moiety of LPS primary plays protective roles for bacteria such as prevention from complement attacks or camouflage with common host carbohydrate residues. The lipid moiety, termed lipid A, is recognized by the Toll-like receptor 4 (TLR4/MD-2 complex, which transduces signals for activation of host innate immunity. The basic structure of lipid A is a glucosamine disaccharide substituted by phosphate groups and acyl groups. Lipid A with 6 acyl groups (hexa-acylated form has been indicated to be a strong stimulator of the TLR4/MD-2 complex. This type of lipid A is conserved among a wide variety of Gram-negative bacteria, and those bacteria are easily recognized by host cells for activation of defensive innate immune responses. Modifications of the lipid A structure to less-acylated forms have been observed in some bacterial species, and those forms are poor stimulators of the TLR4/MD-2 complex. Such modifications are thought to facilitate bacterial evasion of host innate immunity, thereby enhancing pathogenicity. This hypothesis is supported by studies of Yersinia pestis LPS, which contains hexa-acylated lipid A when the bacterium grows at 27ºC (the temperature of the vector flea, and shifts to contain less-acylated forms when grown at the human body temperature of 37ºC. This alteration of lipid A forms following transmission of Y. pestis from fleas to humans contributes predominantly to the virulence of this bacterium over other virulence factors. A similar role for less-acylated lipid A forms has been indicated in some other bacterial species, such as Francisella tularensis, Helicobacter pylori, and Porphyromonas gingivalis, and further studies to explore this concept are

  4. Structure of rat behavior in hole-board: II) multivariate analysis of modifications induced by diazepam.

    Science.gov (United States)

    Casarrubea, Maurizio; Sorbera, Filippina; Crescimanno, Giuseppe

    2009-03-23

    In our previous study we suggested that multivariate analysis could improve hole-board test reliability providing a more useful tool to determine behavioral effects of anxiolytic drugs. To support this hypothesis, a multivariate analysis of rat behavior in hole-board, following administration of the reference anxiolytic drug diazepam, was carried out. Four groups, each composed of thirty male Wistar rats, were used: one saline and three diazepam injected (0.25, 0.5 and 2 mg/kg IP). Rat behavior was recorded for 10 min through a digital videocamera. Descriptive and multivariate analyses were carried out. In all groups, more than 80% of whole behavioral structure encompassed walking, climbing, rearing, immobile-sniffing, edge-sniff and head-dip. Moreover, modifications observed of a specific index, represented by edge-sniff/head-dip ratio, were correlated to diazepam-induced modifications of anxiety level. Cluster analysis showed that diazepam at 0.5 and 2 mg/kg induced important changes for [edge-sniff/head-dip] cluster. In addition, in all diazepam groups a [walking/climbing] cluster appeared. Path diagrams showed close relationships among different patterns both in saline and diazepam injected animals. Also, significant changes were detected following diazepam for transitions encompassing both general exploratory patterns (walking, climbing) and the specific ones (head-dip and edge-sniff). Adjusted residuals confirmed in all groups patterns relationships and, where present, significant behavioral associations. Results demonstrate that an anxiolytic activity can be revealed by head-dip/edge-sniff association weakening and by the addressing of behavioral structure toward general exploratory activity. Improvement of hole-board test reliability in behavioral study of anxiety, following multivariate analysis, is emphasized.

  5. Enzymatic modification of bacterial exopolysaccharides : xanthan lyase as a tool for structural and functional modification of xanthan

    NARCIS (Netherlands)

    Ruijssenaars, H.J.

    2001-01-01

    Bacterial extracellular polysaccharides (EPSs) can be applied, e.g., in foods, as a thickener or stabilizer. The functional properties that make a polysaccharide suitable for such applications are largely determined by the primary structure, i.e., the sugar composition, the linkage types

  6. Ion-induced effects on metallic nanoparticles; Ioneninduzierte Effekte an metallischen Nanoteilchen

    Energy Technology Data Exchange (ETDEWEB)

    Klimmer, Andreas

    2010-02-25

    This work deals with the ion-irradiation of metallic nanoparticles in combination with various substrates. Particle diameters were systematically varied within the range of 2.5-14 nm, inter-particle distances range from 30-120 nm. Irradiations were performed with various inert gas ions with energies of 200 keV, resulting in an average ion range larger than the particle dimensions and therefore the effects of irradiation are mainly due to creation of structural defects within the particles and the underlying substrate as well. The main part of this work deals with ion-induced burrowing of metallic nanoparticles into the underlying substrate. The use of micellar nanoparticles with sharp size distribution combined with AFM and TEM analysis allows a much more detailed look at this effect than other works on that topic so far. With respect to the particle properties also a detailed look on the effect of irradiation on the particle structure would be interesting, which might lead to a deliberate influence on magnetic properties, for example. Within the context of this work, first successful experiments were performed on FePt particles, showing a significant reduction of the ordering temperature leading to the magnetically interesting, ordered L1{sub 0} phase. (orig.)

  7. Radiation Resistance of the U(Al, Si)₃ Alloy: Ion-Induced Disordering.

    Science.gov (United States)

    Meshi, Louisa; Yaniv, Gili; Horak, Pavel; Vacik, Jiri; Mykytenko, Natalia; Rafailov, Gennady; Dahan, Itzchak; Fuks, David; Kiv, Arik

    2018-02-02

    During the exploitation of nuclear reactors, various U-Al based ternary intermetallides are formed in the fuel-cladding interaction layer. Structure and physical properties of these intermetallides determine the radiation resistance of cladding and, ultimately, the reliability and lifetime of the nuclear reactor. In current research, U(Al, Si)₃ composition was studied as a potential constituent of an interaction layer. Phase content of the alloy of an interest was ordered U(Al, Si)₃, structure of which was reported earlier, and pure Al (constituting less than 20 vol % of the alloy). This alloy was investigated prior and after the irradiation performed by Ar ions at 30 keV. The irradiation was performed on the transmission electron microscopy (TEM, JEOL, Japan) samples, characterized before and after the irradiation process. Irradiation induced disorder accompanied by stress relief. Furthermore, it was found that there is a dose threshold for disordering of the crystalline matter in the irradiated region. Irradiation at doses equal or higher than this threshold resulted in almost solely disordered phase. Using the program "Stopping and Range of Ions in Matter" (SRIM), the parameters of penetration of Ar ions into the irradiated samples were estimated. Based on these estimations, the dose threshold for ion-induced disordering of the studied material was assessed.

  8. Radiation Resistance of the U(Al, Si3 Alloy: Ion-Induced Disordering

    Directory of Open Access Journals (Sweden)

    Louisa Meshi

    2018-02-01

    Full Text Available During the exploitation of nuclear reactors, various U-Al based ternary intermetallides are formed in the fuel-cladding interaction layer. Structure and physical properties of these intermetallides determine the radiation resistance of cladding and, ultimately, the reliability and lifetime of the nuclear reactor. In current research, U(Al, Si3 composition was studied as a potential constituent of an interaction layer. Phase content of the alloy of an interest was ordered U(Al, Si3, structure of which was reported earlier, and pure Al (constituting less than 20 vol % of the alloy. This alloy was investigated prior and after the irradiation performed by Ar ions at 30 keV. The irradiation was performed on the transmission electron microscopy (TEM, JEOL, Japan samples, characterized before and after the irradiation process. Irradiation induced disorder accompanied by stress relief. Furthermore, it was found that there is a dose threshold for disordering of the crystalline matter in the irradiated region. Irradiation at doses equal or higher than this threshold resulted in almost solely disordered phase. Using the program “Stopping and Range of Ions in Matter” (SRIM, the parameters of penetration of Ar ions into the irradiated samples were estimated. Based on these estimations, the dose threshold for ion-induced disordering of the studied material was assessed.

  9. Controlled modification of the structure of polymer surfaces by chemically grafting inorganic species

    Directory of Open Access Journals (Sweden)

    Oréfice Rodrigo Lambert

    1999-01-01

    Full Text Available Many chemical and physical methods, such as plasma, e-beam, sputtering, CVD and others, have been used to modify the structure of polymer surfaces by depositing thin inorganic films. Most of these techniques are based upon the use of high energy sources that ultimately can damage either chemically or physically polymer surfaces. Moreover, these methods are usually not versatile enough to allow the design of structurally and chemically tailored surfaces through the control of the distribution of chemical functionalities throughout the surface. In this work, inorganic species were introduced onto polymer substrates in a controlled manner by performing a sequence of chemical reactions at the surface. Sulfonation followed by silanization reactions were used to graft alkoxysilane species at the surface of poly(aryl sulfones. The heterogeneous chemical modification of poly(aryl sulfones was monitored by FTIR-ATR (Attenuated Total Reflection - FTIR. Model compounds were used to study the chemical reactions occurring during the grafting procedure. The results showed that the developed procedure can allow a controlled introduction of inorganic species onto polymer surfaces. Furthermore, in order to prove that this procedure enables the deposition of specific chemical functionalities onto polymer surfaces that can be used to create chemically and structurally tailored surfaces, silicate films were deposited on previously silanated PAS bioactive glass composites. In vitro tests showed that the surface modified composite can enhance the rates of hydroxy-carbonate-apatite precipitation.

  10. Structure and mutagenesis of the DNA modification-dependent restriction endonuclease AspBHI.

    Science.gov (United States)

    Horton, John R; Nugent, Rebecca L; Li, Andrew; Mabuchi, Megumu Yamada; Fomenkov, Alexey; Cohen-Karni, Devora; Griggs, Rose M; Zhang, Xing; Wilson, Geoffrey G; Zheng, Yu; Xu, Shuang-yong; Cheng, Xiaodong

    2014-03-07

    The modification-dependent restriction endonuclease AspBHI recognizes 5-methylcytosine (5mC) in the double-strand DNA sequence context of (C/T)(C/G)(5mC)N(C/G) (N = any nucleotide) and cleaves the two strands a fixed distance (N12/N16) 3' to the modified cytosine. We determined the crystal structure of the homo-tetrameric AspBHI. Each subunit of the protein comprises two domains: an N-terminal DNA-recognition domain and a C-terminal DNA cleavage domain. The N-terminal domain is structurally similar to the eukaryotic SET and RING-associated (SRA) domain, which is known to bind to a hemi-methylated CpG dinucleotide. The C-terminal domain is structurally similar to classic Type II restriction enzymes and contains the endonuclease catalytic-site motif of DX20EAK. To understand how specific amino acids affect AspBHI recognition preference, we generated a homology model of the AspBHI-DNA complex, and probed the importance of individual amino acids by mutagenesis. Ser41 and Arg42 are predicted to be located in the DNA minor groove 5' to the modified cytosine. Substitution of Ser41 with alanine (S41A) and cysteine (S41C) resulted in mutants with altered cleavage activity. All 19 Arg42 variants resulted in loss of endonuclease activity.

  11. Modification of the structural and optical properties of commercial ZnO powder by mechanical activation

    Directory of Open Access Journals (Sweden)

    Šćepanović M.

    2006-01-01

    Full Text Available Mechanical activation was used as a method for modification of the structural and optical properties of commercial ZnO powder. For this purpose zinc oxide powder was mechanically treated by grinding in a high-energy vibro-mill in a continual regime in air up to 300 minutes. Starting and modified ZnO samples were characterized using XRD, BET and TEM measurements. Optical properties of these samples were investigated by Raman and photoluminescence (PL spectroscopy. The color of commercial ZnO powder was white while mechanically activated ZnO powder was dark yellow, indicating the presence of nonstoichiometry. In the Raman spectra of non-activated sample Raman modes of bulk ZnO were observed, while the spectra of modified samples point out structural and stoichiometric changes. The PL spectra of modified samples excited by 325 and 442 nm lines of a He-Cd laser show great difference with respect to the spectra of the original sample. This study confirms that change in the defect structure of the ZnO crystal lattice introduced by mechanical activation affects the optical properties of this material.

  12. Investigation of structural modification and thermal characteristics of lignin after heat treatment.

    Science.gov (United States)

    Kim, Jae-Young; Hwang, Hyewon; Oh, Shinyoung; Kim, Yong-Sik; Kim, Ung-Jin; Choi, Joon Weon

    2014-05-01

    Milled wood lignin was subjected to heat treatment between 150 and 300°C to understand the pattern of its structural modification and thermal properties. When the temperature was elevated with interval of 50°C, the color of the lignin became dark brown and the lignin released various forms of phenols from terminal phenolic groups in the lignin, leading to two physical phenomena: (1) gradual weight loss of the lignin, up to 19% based on dry weight and (2) increase in the carbon content and decrease in the oxygen content. Nitrobenzene oxidation and (13)C NMR analyses confirmed a cleavage of β-O-4 linkage (depolymerization) and reduction of methoxyl as well as phenolic hydroxyl group were also characteristic in the lignin structure during heat treatment. Simultaneously with lignin depolymerization, GPC analysis provided a possibility that condensation between lignin fragments could also occur during heat treatment. TGA/DTG/DSC data revealed that thermal stability of lignin obviously increased after heat treatment, implicating the structural rearrangement of lignin to reduction of β-O-4 linkage as well as accumulation of CC bonds. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. A study of ion-induced phase transformation in austenitic stainless steel

    International Nuclear Information System (INIS)

    Sakamoto, Isao

    1993-01-01

    The phase stability of austenitic stainless steel in an irradiation environment using low-nickel 17/7, 17/13 steel and commercial steel such as 304 and 316 steel as well as high-nickel 310 steel in order to investigate a mechanism of the ion-induced phase transformation were studied. The irradiation in steel was performed with steel constituent elements (Fe, Cr and Ni ions) and also with rare-gas elements such as Ar, Kr and Xe ions at room temperature. In addition, He, H, D and N 2 ions were irradiated in steel complementarily. The modification in the near surface region of the irradiated steel has been observed by means of conversion electron Moessbauer spectroscopy (CEMS), glancing angle X-ray diffraction (GXRD), Rutherford backscattering (RBS) and particle-induced X-ray emission (PIXE). It has been considered that the phase transformation in steel after irradiation of Ni ions was stress-induced due to a stress field around damages accumulated by irradiation. On the other hand, for Fe ion irradiation in steel, we have confirmed that the increase of Fe constituent atoms induced the phase transformation. For rare-gas ion irradiation in steel, it has been suggested that implanted rare-gas atoms aggregated and formed highly pressurized rare-gas inclusion. In both metal ion and rare-gas ion irradiation, the austenite stability was demonstrated to be well correlated with the phase conditions of the Schaffler diagram, and it has been established that the primary contribution to the driving force for these transformation comes from relief of high stress levels in the implanted layer. (J.P.N.) 76 refs

  14. Amyloid-β peptides time-dependent structural modifications: AFM and voltammetric characterization.

    Science.gov (United States)

    Enache, Teodor Adrian; Chiorcea-Paquim, Ana-Maria; Oliveira-Brett, Ana Maria

    2016-07-05

    The human amyloid beta (Aβ) peptides, Aβ1-40 and Aβ1-42, structural modifications, from soluble monomers to fully formed fibrils through intermediate structures, were investigated, and the results were compared with those obtained for the inverse Aβ40-1 and Aβ42-1, mutant Aβ1-40Phe(10) and Aβ1-40Nle(35), and rat Aβ1-40Rat peptide sequences. The aggregation was followed at a slow rate, in chloride free media and room temperature, and revealed to be a sequence-structure process, dependent on the physicochemical properties of each Aβ peptide isoforms, and occurring at different rates and by different pathways. The fibrilization process was investigated by atomic force microscopy (AFM), via changes in the adsorption morphology from: (i) initially random coiled structures of ∼0.6 nm height, corresponding to the Aβ peptide monomers in random coil or in α-helix conformations, to (ii) aggregates and protofibrils of 1.5-6.0 nm height and (iii) two types of fibrils, corresponding to the Aβ peptide in a β-sheet configuration. The reactivity of the carbon electrode surface was considered. The hydrophobic surface induced rapid changes of the Aβ peptide conformations, and differences between the adsorbed fibrils, formed at the carbon surface (beaded, thin, 2.0 nm height), were detected. Differential pulse voltammetry showed that, according to their primary structure, the Aβ peptides undergo oxidation in one or two steps, the first step corresponding to the tyrosine amino acids oxidation, and the second one to the histidine and methionine amino acids oxidation. The fibrilization process was electrochemically detected via the decrease of the Aβ peptide oxidation peak currents that occurred in a time dependent manner. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Modification of Flow Structure Over a Van Model By Suction Flow Control to Reduce Aerodynamics Drag

    Directory of Open Access Journals (Sweden)

    Harinaldi Harinaldi

    2012-05-01

    Full Text Available Automobile aerodynamic studies are typically undertaken to improve safety and increase fuel efficiency as well as to  find new innovation in automobile technology to deal with the problem of energy crisis and global warming. Some car companies have the objective to develop control solutions that enable to reduce the aerodynamic drag of vehicle and  significant modification progress is still possible by reducing the mass, rolling friction or aerodynamic drag. Some flow  control method provides the possibility to modify the flow separation to reduce the development of the swirling structures around the vehicle. In this study, a family van is modeled with a modified form of Ahmed's body by changing the orientation of the flow from its original form (modified/reversed Ahmed body. This model is equipped with a suction on the rear side to comprehensively examine the pressure field modifications that occur. The investigation combines computational and experimental work. Computational approach used  a commercial software with standard k-epsilon flow turbulence model, and the objectives was  to determine the characteristics of the flow field and aerodynamic drag reduction that occurred in the test model. Experimental approach used load cell in order to validate the aerodynamic drag reduction obtained by computational approach. The results show that the application of a suction in the rear part of the van model give the effect of reducing the wake and the vortex formation. Futhermore, aerodynamic drag reduction close to 13.86% for the computational approach and 16.32% for the experimental have been obtained.

  16. Surface modification induced phase transformation and structure variation on the rapidly solidified recast layer of titanium

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Ming-Hung [Department of Mechanical Engineering and Graduate Institute of Mechanical and Precision Engineering, National Kaoshiung University of Applied Sciences, Kaoshiung 807, Taiwan (China); School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Haung, Chiung-Fang [School of Dental Technology, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Division of Family and Operative Dentistry, Department of Dentistry, Taipei Medical University Hospital, Taipei 110, Taiwan (China); Research Center for Biomedical Devices and Prototyping Production, Taipei Medical University, Taipei 110, Taiwan (China); Shyu, Shih-Shiun [Department of Dentistry, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, New Taipei City 231, Taiwan (China); Chou, Yen-Ru [Research Center for Biomedical Devices and Prototyping Production, Taipei Medical University, Taipei 110, Taiwan (China); Graduate Institute of Biomedical Materials and Tissue Engineering, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei 110, Taiwan (China); Lin, Ming-Hong [Department of Mechanical Engineering and Graduate Institute of Mechanical and Precision Engineering, National Kaoshiung University of Applied Sciences, Kaoshiung 807, Taiwan (China); Peng, Pei-Wen, E-mail: apon@tmu.edu.tw [School of Dental Technology, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); and others

    2015-08-15

    In this study, neodymium-doped yttrium orthovanadate (Nd:YVO{sub 4}) as a laser source with different scanning speeds was used on biomedical Ti surface. The microstructural and biological properties of laser-modified samples were investigated by means of optical microscope, electron microscope, X-ray diffraction, surface roughness instrument, contact angle and cell cytotoxicity assay. After laser modification, the rough volcano-like recast layer with micro-/nanoporous structure and wave-like recast layer with nanoporous structure were generated on the surfaces of laser-modified samples, respectively. It was also found out that, an α → (α + rutile-TiO{sub 2}) phase transition occurred on the recast layers of laser-modified samples. The Ti surface becomes hydrophilic at a high speed laser scanning. Moreover, the cell cytotoxicity assay demonstrated that laser-modified samples did not influence the cell adhesion and proliferation behaviors of osteoblast (MG-63) cell. The laser with 50 mm/s scanning speed induced formation of rough volcano-like recast layer accompanied with micro-/nanoporous structure, which can promote cell adhesion and proliferation of MG-63 cell on Ti surface. The results indicated that the laser treatment was a potential technology to enhance the biocompatibility for titanium. - Highlights: • Laser induced the formation of recast layer with micro-/nanoporous structure on Ti. • An α → (α + rutile-TiO{sub 2}) phase transition was observed within the recast layer. • The Ti surface becomes hydrophilic at a high speed laser scanning. • Laser-modified samples exhibit good biocompatibility to osteoblast (MG-63) cell.

  17. Porphyrin mediated photo-modification of the structure and function of human serum albumin

    Science.gov (United States)

    Rozinek, Sarah C.

    Photosensitization reactions involve irradiating (with visible light) molecules with a high efficiency for either electron transfer or entering an excited triplet state (photosensitizer). Such reactions are applied to photodynamic cancer therapy, many medical laser-treatments, and a potential array of disinfection and pest elimination techniques. To understand the biophysical mechanisms of how these applications are effective at the protein level, the group of Dr. Brancaleon (UTSA) has investigated the irradiation of several dye-protein combinations, and discovered effects on protein structure and function. To further that work, we have investigated irradiation of the protein, human serum albumin (HSA), photosensitized by either protoporphyrin IX (PPIX) or meso-tetrakis(4-sulfonatophenyl)porphyrin (TSPP). HSA is the most abundant plasma protein, making it a likely substrate in PDT, and it possesses a specific binding pocket for iron-PPIX (heme) and possibly other porphyrin derivatives. The results of our research are summarized as follows. First, a thorough characterization of the binding of each photosensitizer to albumin was completed, elucidating a probable binding location for TSPP. Next, fluorescence lifetime emission of the single tryptophan residue, alongside circular dichroism, found tertiary structural changes around tryptophan and an overall 20% decrease in protein secondary structure after irradiation with TSPP bound. Finally, to determine if protein function was lost after photosensitization, size exclusion chromatography found modified albumin still recognizable by its receptor-protein, and comparative ex vivo up-take studies revealed that modified albumin is not processed the same way as native albumin in live tapeworm larva (Mesocestoides corti). Thus we found that visible light can induce partial unfolding of a protein by using a photo-activated ligand. These small structural modifications were sufficient to affect the protein's biological function.

  18. Plant-derived phenolics inhibit the accrual of structurally characterised protein and lipid oxidative modifications.

    Directory of Open Access Journals (Sweden)

    Arantza Soler-Cantero

    Full Text Available Epidemiological data suggest that plant-derived phenolics beneficial effects include an inhibition of LDL oxidation. After applying a screening method based on 2,4-dinitrophenyl hydrazine-protein carbonyl reaction to 21 different plant-derived phenolic acids, we selected the most antioxidant ones. Their effect was assessed in 5 different oxidation systems, as well as in other model proteins. Mass-spectrometry was then used, evidencing a heterogeneous effect on the accumulation of the structurally characterized protein carbonyl glutamic and aminoadipic semialdehydes as well as for malondialdehyde-lysine in LDL apoprotein. After TOF based lipidomics, we identified the most abundant differential lipids in Cu(++-incubated LDL as 1-palmitoyllysophosphatidylcholine and 1-stearoyl-sn-glycero-3-phosphocholine. Most of selected phenolic compounds prevented the accumulation of those phospholipids and the cellular impairment induced by oxidized LDL. Finally, to validate these effects in vivo, we evaluated the effect of the intake of a phenolic-enriched extract in plasma protein and lipid modifications in a well-established model of atherosclerosis (diet-induced hypercholesterolemia in hamsters. This showed that a dietary supplement with a phenolic-enriched extract diminished plasma protein oxidative and lipid damage. Globally, these data show structural basis of antioxidant properties of plant-derived phenolic acids in protein oxidation that may be relevant for the health-promoting effects of its dietary intake.

  19. Modification of mechanical properties of single crystal aluminum oxide by ion beam induced structural changes

    International Nuclear Information System (INIS)

    Ensinger, W.; Nowak, R.; Horino, Y.; Baba, K.

    1993-01-01

    The mechanical behaviour of ceramics is essentially determined by their surface qualities. As a surface modification technique, ion implantation provides the possibility to modify the mechanical properties of ceramics. Highly energetic ions are implanted into the near-surface region of a material and modify its composition and structure. Ions of aluminum, oxygen, nickel and tantalum were implanted into single-crystal α-aluminum oxide. Three-point bending tests showed that an increase in flexural strength of up to 30% could be obtained after implantation of aluminum and oxygen. Nickel and tantalum ion implantation increased the fracture toughness. Indentation tests with Knoop and Vickers diamonds and comparison of the lengths of the developed radial cracks showed that ion implantation leads to a reaction in cracking. The observed effects are assigned to radiation induced structural changes of the ceramic. Ion bombardment leads to radiation damage and formation of compressive stress. In case of tantalum implantation, the implanted near-surface zone becomes amorphous. These effects make the ceramic more resistant to fracture. (orig.)

  20. Structure Modification of an Active Azo-Compound as a Route to New Antimicrobial Compounds

    Directory of Open Access Journals (Sweden)

    Simona Concilio

    2017-05-01

    Full Text Available Some novel (phenyl-diazenylphenols 3a–g were designed and synthesized to be evaluated for their antimicrobial activity. A previously synthesized molecule, active against bacteria and fungi, was used as lead for modifications and optimization of the structure, by introduction/removal or displacement of hydroxyl groups on the azobenzene rings. The aim of this work was to evaluate the consequent changes of the antimicrobial activity and to validate the hypothesis that, for these compounds, a plausible mechanism could involve an interaction with protein receptors, rather than an interaction with membrane. All newly synthesized compounds were analyzed by 1H-NMR, DSC thermal analysis and UV-Vis spectroscopy. The in vitro minimal inhibitory concentrations (MIC of each compound was determined against Gram-positive and Gram-negative bacteria and Candida albicans. Compounds 3b and 3g showed the highest activity against S. aureus and C. albicans, with remarkable MIC values of 10 µg/mL and 3 µg/mL, respectively. Structure-activity relationship studies were capable to rationalize the effect of different substitutions on the phenyl ring of the azobenzene on antimicrobial activity.

  1. A structural model of health behavior modification among patients with cardiovascular disease.

    Science.gov (United States)

    Goong, Hwasoo; Ryu, Seungmi; Xu, Lijuan

    2016-02-01

    The purpose of the study was to test a structural equation model in which social support, health beliefs, and stage of change predict the health behaviors of patients with cardiovascular disease. A cross-sectional correlational design was used. Using convenience sampling, a survey about social support, health belief, stage of change, and health behavior was completed by 314 adults with cardiovascular disease from outpatient clinics in 2 university hospitals in Korea. Data were analyzed using a structural equation model with the Analysis of Moment program. The participants were aged 53.44±13.19 years (mean±SD), and about 64% of them were male. The proposed model fit the data from the study well, explaining 19% and 60% of the variances in the stage of change and health behavior, respectively. The findings indicate that the performance of health behavior modification among the patients with cardiovascular disease can be explained by social support, health belief, and stage of change based on a health-belief and stage-of-change model. Further studies are warranted to confirm the efficacy of health-promoting strategies in initiating and maintaining the performance of health behaviors by providing social support from family and medical staff and enhancing health belief. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. Engine structure modifications effect on the flow behavior, combustion, and performance characteristics of DI diesel engine

    International Nuclear Information System (INIS)

    Taghavifar, Hadi; Khalilarya, Shahram; Jafarmadar, Samad

    2014-01-01

    Highlights: • Engine geometrical configuration was modified based on bowl radius and displacement. • The best engine performance indices associated with D3 and R1 structures. • Increasing the bowl radius and outward bowl displacement increases ignition delay. • The best configuration for uniform air/fuel mixture, TKE, and temperature is found. - Abstract: The simulation was carried out based on 1.8 L Ford diesel engine and the geometrical modification in structure of piston were considered in terms of bowl movement and the bowl size in four equal increments. Two major conflicting parameters in combustion and engine efficiency were taken into account and visualized in contour plots as the bowl geometry was varied: (1) the air/fuel mixing process demonstrated by Homogeneity Factor and equivalence ratio, (2) combustion initiation and work delivery by heat release rate, pressure curves, and indicated thermal efficiency. A new version of Coherent Flame Model’s sub-model (ECFM-3Z) was adopted during the calculations to shed light into the combustion chemistry and reaction rate in detail. It was found that the bowl displacement toward the cylinder wall, increases the mixture uniformity (higher HF) thus higher pressure and heat release rate peak were obtained with the penalty of combustion delay which substantially reduces the effective in-cylinder pressure. Furthermore, it was demonstrated that smaller bowl size induces better squish and vortex formation in the chamber, although lesser spray penetration and flame quenching owing to the spray-wall impingement reduces ignition delay

  3. Structure Modification of an Active Azo-Compound as a Route to New Antimicrobial Compounds.

    Science.gov (United States)

    Concilio, Simona; Sessa, Lucia; Petrone, Anna Maria; Porta, Amalia; Diana, Rosita; Iannelli, Pio; Piotto, Stefano

    2017-05-25

    Some novel (phenyl-diazenyl)phenols 3a - g were designed and synthesized to be evaluated for their antimicrobial activity. A previously synthesized molecule, active against bacteria and fungi, was used as lead for modifications and optimization of the structure, by introduction/removal or displacement of hydroxyl groups on the azobenzene rings. The aim of this work was to evaluate the consequent changes of the antimicrobial activity and to validate the hypothesis that, for these compounds, a plausible mechanism could involve an interaction with protein receptors, rather than an interaction with membrane. All newly synthesized compounds were analyzed by ¹H-NMR, DSC thermal analysis and UV-Vis spectroscopy. The in vitro minimal inhibitory concentrations (MIC) of each compound was determined against Gram-positive and Gram-negative bacteria and Candida albicans . Compounds 3b and 3g showed the highest activity against S. aureus and C. albicans , with remarkable MIC values of 10 µg/mL and 3 µg/mL, respectively. Structure-activity relationship studies were capable to rationalize the effect of different substitutions on the phenyl ring of the azobenzene on antimicrobial activity.

  4. Modeling ion induced effects in thin films and coatings for lunar and space environment applications

    Science.gov (United States)

    Taylor, Edward W.; Pirich, Ronald

    2013-09-01

    Protective thin film coatings are important for many near-Earth and interplanetary space systems applications using photonic components, optical elements, solar cells and detector-sensor front surfaces to name but a few environmentally at-risk technologies. The near-Earth and natural space environment consists of known degradation processes induced within these technologies brought about by atomic oxygen, micrometeorite impacts, space debris and dust, solar generated charged particles, Van Allen belt trapped particles, and galactic cosmic radiation. This paper will focus on presenting the results of an investigation based on simulated ion-induced defect-modeling and nuclear irradiation testing of several innovative hybrid-polymeric self-cleaning hydrophobic coatings investigated for application to space photonic components, lunar surface, avionic and terrestrial applications. Data is reported regarding the radiation resistance of several hybrid polymer coatings containing various loadings of nanometer-sized TiO2 fillers for protecting sensors, structures, human and space vehicles from dust contamination found in space and on the Lunar and other planetary surfaces.

  5. Modification of polyacrylonitrile carbon fibers by highfluence ion irradiation

    Science.gov (United States)

    Andrianova, N. N.; Borisov, A. M.; Kazakov, V. A.; Mashkova, E. S.; Ovchinnikov, M. A.; Savushkina, S. V.; Chernenko, N. M.

    2017-12-01

    The Raman spectroscopy has been used to analyse ion-induced modifications of carbon PAN-fiber shell due to 10-30 keV Ar+ high fluence ion irradiation at normal and oblique incidence in the temperature range from RT to 400 °C. It has shown that formed in ion-induced processes of amorphization, recrystallization and crimping the modifications of PAN-fiber shell are characterized by the presence of the amorphous phase with the A peak in the Raman spectra and the increased intensity of the D peak relative to the G peak in comparison with non-irradiated fiber. Amorphous phase in the PAN-fiber shell is the highest in case of amorphization and the least at the crimping. The increased intensity of the D peak in the Raman spectra and the G peak shift towards higher frequencies during recrystallization and crimping indicates ion-induced nanostructuring of the PAN- fiber shell.

  6. Role of post-translational modifications on structure, function and pharmacology of class C G protein-coupled receptors

    DEFF Research Database (Denmark)

    Nørskov-Lauritsen, Lenea; Bräuner-Osborne, Hans

    2015-01-01

    taste receptors (T1R1-3), one calcium-sensing (CaS) receptor, one GPCR, class C, group 6, subtype A (GPRC6) receptor, and seven orphan receptors. G protein-coupled receptors undergo a number of post-translational modifications, which regulate their structure, function and/or pharmacology. Here, we...

  7. INFLUENCE OF MODIFICATION ON THE STRUCTURE AND CHARACTERISTICS OF THE STAINLESS STEEL 12X18H10TL

    Directory of Open Access Journals (Sweden)

    I. V. Zemskov

    2004-01-01

    Full Text Available There are given the results of investigation of influence of modification by ferrocerium, FS30RZM30B, FSMG, modifier MN, developed in BNTU, ferromolybdenum on the structure and characteristics of the steel 12X18H10TL.

  8. Structural modifications of AlInN/GaN thin films by neon ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Majid, Abdul, E-mail: abdulmajid40@yahoo.com [Department of Physics, University of Gujrat, Gujrat 50700 (Pakistan); Husnain, G.; Usman, Muhammad [Experimental Physics Labs, National Centre for Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Shakoor, Abdul [Department of Physics, Bahauddin Zakariya University, Multan (Pakistan); Hassan, Najmul [Department of Physics, Hazara University, Mansehra (Pakistan); Zhu, J.J. [Nano Fabrication Facility, Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou (China)

    2013-12-02

    To study ion beam induced modifications into MOCVD grown wurtzite AlInN layers, neon ions were implanted on the samples with four doses ranging from 10{sup 14} to 9×10{sup 15} ions/cm{sup 2}. Structural characterization was carried out by X-ray diffraction and Rutherford backscattering spectroscopy (RBS) techniques. XRD analysis revealed that GaN related peak for all samples remains at its usual Bragg position of 2θ=34.56° whereas a shift in AlInN peak takes place from its position of 2θ=35.51° for as-grown sample. Rutherford back scattering (RBS) analysis indicated that peak related to Ga atoms in capping layer provided evidence of partial sputtering of GaN cap layers. Moreover, Al peak position is shifted towards lower channel side and width of the signal is increased after implantation, which pointed to the inwards migration of Al atoms away from the AlInN surface. The results suggested that partial sputtering of cap layer has taken place without uncovering the underneath AlInN layer.

  9. Structural analysis of DNA–protein complexes regulating the restriction–modification system Esp1396I

    International Nuclear Information System (INIS)

    Martin, Richard N. A.; McGeehan, John E.; Ball, Neil J.; Streeter, Simon D.; Thresh, Sarah-Jane; Kneale, G. G.

    2013-01-01

    Comparison of bound and unbound DNA in protein–DNA co-crystal complexes reveals insights into controller-protein binding and DNA distortion in transcriptional regulation. The controller protein of the type II restriction–modification (RM) system Esp1396I binds to three distinct DNA operator sequences upstream of the methyltransferase and endonuclease genes in order to regulate their expression. Previous biophysical and crystallographic studies have shown molecular details of how the controller protein binds to the operator sites with very different affinities. Here, two protein–DNA co-crystal structures containing portions of unbound DNA from native operator sites are reported. The DNA in both complexes shows significant distortion in the region between the conserved symmetric sequences, similar to that of a DNA duplex when bound by the controller protein (C-protein), indicating that the naked DNA has an intrinsic tendency to bend when not bound to the C-protein. Moreover, the width of the major groove of the DNA adjacent to a bound C-protein dimer is observed to be significantly increased, supporting the idea that this DNA distortion contributes to the substantial cooperativity found when a second C-protein dimer binds to the operator to form the tetrameric repression complex

  10. Structural modifications of the brain in acclimatization to high-altitude.

    Directory of Open Access Journals (Sweden)

    Jiaxing Zhang

    Full Text Available Adaptive changes in respiratory and cardiovascular responses at high altitude (HA have been well clarified. However, the central mechanisms underlying HA acclimatization remain unclear. Using voxel-based morphometry (VBM and diffusion tensor imaging (DTI with fractional anisotropy (FA calculation, we investigated 28 Han immigrant residents (17-22 yr born and raised at HA of 2616-4200 m in Qinghai-Tibetan Plateau for at least 17 years and who currently attended college at sea-level (SL. Their family migrated from SL to HA 2-3 generations ago and has resided at HA ever since. Control subjects were matched SL residents. HA residents (vs. SL showed decreased grey matter volume in the bilateral anterior insula, right anterior cingulate cortex, bilateral prefrontal cortex, left precentral cortex, and right lingual cortex. HA residents (vs. SL had significantly higher FA mainly in the bilateral anterior limb of internal capsule, bilateral superior and inferior longitudinal fasciculus, corpus callosum, bilateral superior corona radiata, bilateral anterior external capsule, right posterior cingulum, and right corticospinal tract. Higher FA values in those regions were associated with decreased or unchanged radial diffusivity coinciding with no change of longitudinal diffusivity in HA vs. SL group. Conversely, HA residents had lower FA in the left optic radiation and left superior longitudinal fasciculus. Our data demonstrates that HA acclimatization is associated with brain structural modifications, including the loss of regional cortical grey matter accompanied by changes in the white matter, which may underlie the physiological adaptation of residents at HA.

  11. Malassezia globosa MgMDL2 lipase: Crystal structure and rational modification of substrate specificity.

    Science.gov (United States)

    Lan, Dongming; Xu, Huan; Xu, Jinxin; Dubin, Grzegorz; Liu, Jinsong; Iqbal Khan, Faez; Wang, Yonghua

    2017-06-24

    Lipases play an important role in physiological metabolism and diseases, and also have multiple industrial applications. Rational modification of lipase specificity may increase the commercial utility of this group of enzymes, but is hindered by insufficient mechanistic understanding. Here, we report the 2.0 Å resolution crystal structure of a mono- and di-acylglycerols lipase from Malassezia globosa (MgMDL2). Interestingly, residues Phe278 and Glu282 were found to involve in substrate recognition because mutation on each residue led to convert MgMDL2 to a triacylglycerol (TAG) lipase. The Phe278Ala and Glu282Ala mutants also acquired ability to synthesize TAGs by esterification of glycerol and fatty acids. By in silicon analysis, steric hindrance of these residues seemed to be key factors for the altered substrate specificity. Our work may shed light on understanding the unique substrate selectivity mechanism of mono- and di-acylglycerols lipases, and provide a new insight for engineering biocatalysts with desired catalytic behaviors for biotechnological application. Copyright © 2017 Elsevier Inc. All rights reserved.

  12. Structural modification of coal-tar pitch fractions during mild oxidation - relevance to carbonization behavior

    Energy Technology Data Exchange (ETDEWEB)

    Machnikowski, J.; Kaczmarska, H.; Gerus-Piasecka, I.; Diez, M.A.; Alvarez, R.; Garcia, R. [Wroclaw University of Technology, Wroclaw (Poland)

    2002-07-01

    Modified pitches with softening points of about 175{degree}C were prepared by air-blowing at 300{degree}C of coal-tar pitches from different commercial coke-oven tars. The modifications induced by the mild oxidation were monitored using solvent and extrographic fractionation, elemental analysis, H-1 NMR and HPLC. Optical microscopy was used to follow the effect of air-blowing on carbonization behaviour. Low molecular weight cata-condensed PAHs and those with basic nitrogen and hydroxylic functionalities present in extrographic fractions F2 and F4, respectively, are preferentially polymerized pitch constituents. In contrast, peri-condensed PAHs in extrographic fractions F2 and F3, are practically unreactive under the oxidation conditions used. The mild oxidation enhances the tendency of quinoline insoluble (QI) particles to form aggregates in an early stage of thermal treatment, modifying the mode of mesophase development and leading to a non-homogeneous optical texture. The enhanced propensity of QI to aggregation is discussed in terms of structural peculiarities of the parent pitch and possible oxidative polymerization reactions.

  13. Surface modification induced by UV nanosecond Nd:YVO4 laser structuring on biometals

    Science.gov (United States)

    Fiorucci, M. Paula; López, Ana J.; Ramil, Alberto

    2014-08-01

    Laser surface texturing is a promising tool for improving metallic biomaterials performance in dental and orthopedic bone-replacing applications. Laser ablation modifies the topography of bulk material and might alter surface properties that govern the interactions with the surrounding tissue. This paper presents a preliminary evaluation of surface modifications in two biometals, stainless steel 316L and titanium alloy Ti6Al4V by UV nanosecond Nd:YVO4. Scanning electron microscopy of the surface textured by parallel micro-grooves reveals a thin layer of remelted material along the grooves topography. Furthermore, X-ray diffraction allowed us to appreciate a grain refinement of original crystal structure and consequently induced residual strain. Changes in the surface chemistry were determined by means of X-ray photoelectron spectroscopy; in this sense, generalized surface oxidation was observed and characterization of the oxides and other compounds such hydroxyl groups was reported. In case of titanium alloy, oxide layer mainly composed by TiO2 which is a highly biocompatible compound was identified. Furthermore, laser treatment produces an increase in oxide thickness that could improve the corrosion behavior of the metal. Otherwise, laser treatment led to the formation of secondary phases which might be detrimental to physical and biocompatibility properties of the material.

  14. Synthesis, crystal structure, and properties of two modifications of MgB(12)C(2).

    Science.gov (United States)

    Adasch, Volker; Hess, Kai-Uwe; Ludwig, Thilo; Vojteer, Natascha; Hillebrecht, Harald

    2007-01-01

    Single crystals of two modifications of the new magnesium boride carbide MgB(12)C(2) were synthesized from the elements in a metallic melt by using tantalum ampoules. Crystals were characterized by single-crystal X-ray diffraction and electron microprobe analysis (energy-dispersive (EDX) and wavelength-dispersive (WDX) X-ray spectroscopy). Orthorhombic MgB(12)C(2) is formed in a Cu/Mg melt at 1873 K. The crystal structure of o-MgB(12)C(2) (Imma, Z=4, a=5.6133(10), b=9.828(2), c=7.9329(15) A, 574 reflections, 42 variables, R(1)(F)=0.0208, wR(2)(I)=0.0540) consists of a hexagonal primitive array of B(12) icosahedra with Mg atoms and C(2) units in trigonal-prismatic voids. Each icosahedron has six exohedral B--B and six B--C bonds. Carbon is tetrahedrally coordinated by three boron atoms and one carbon atom with a remarkably long C--C distance of 1.727 A. Monoclinic MgB(12)C(2) is formed in an Al/Mg melt at 1573 K. The structure of m-MgB(12)C(2) (C2/c, Z=4, a=7.2736(11), b=8.7768(13), c=7.2817(11) A, beta=105.33(3) degrees , 1585 reflections, 71 variables, R(1)(F)=0.0228, wR(2)(I)=0.0610) may be described as a distorted cubic close arrangement of B(12) icosahedra. Tetrahedral voids are filled by C atoms and octahedral voids are occupied by Mg atoms. The icosahedra are interconnected by four exohedral B--B bonds to linear chains and by eight interstitial C atoms to form a three-dimensional covalent network. Both compounds fulfill the electron-counting rules of Wade and Longuet-Higgins.

  15. Turbulence modification in bubbly upward pipe flow. Extraction of time resolved turbulent microscopic structure by high speed PIV

    International Nuclear Information System (INIS)

    Yoshimura, Koki; Minato, Daiju; Sato, Yohei; Hishida, Koichi

    2004-01-01

    The objective of the present study is to obtain detailed information on the effects of bubbles on modification of turbulent structure by time-series measurements using a high speed time-resolved PIV. The experiments were carried out in a fully-developed vertical pipe with upflow of water at the Reynolds number of 9700 and the void fraction of 0.5%. It is observed that turbulence production was decreased and the dissipation rate was enhanced in the whole domain. We analyzed the effects of bubbles on modification of the energy cascade process from power spectra of velocity fluctuation of the continuous phase. (author)

  16. Structural, chemical surface and transport modifications of regenerated cellulose dense membranes due to low-dose γ-radiation

    International Nuclear Information System (INIS)

    Vazquez, M.I.; Heredia-Guerrero, J.A.; Galan, P.; Benitez, J.J.; Benavente, J.

    2011-01-01

    Research highlights: → Low dose γ-radiation causes slight structural, chemical and morphological changes on regenerated cellulose films. → Induced structural changes increase the fragility of irradiated films. → Structural modifications reduce ion permeability of films. - Abstract: Modifications caused in commercial dense regenerated cellulose (RC) flat membranes by low-dose γ-irradiation (average photons energy of 1.23 MeV) are studied. Slight structural, chemical and morphological surface changes due to irradiation in three films with different RC content were determined by ATR-FTIR, XRD, XPS and AFM. Also, the alteration of their mechanical elasticity has been studied. Modification of membrane performance was determined from solute diffusion coefficient and effective membrane fixed charge concentration obtained from NaCl diffusion measurements. Induced structural changes defining new and effective fracture propagation directions are considered to be responsible for the increase of fragility of irradiated RC membranes. The same structural changes are proposed to explain the reduction of the membrane ion permeability through a mechanism involving either ion pathways elongation and/or blocking.

  17. Non-linear effect of copper cluster ions induced damage in silicon

    CERN Document Server

    Wang, X M; Shao, L; Liu, J R; Chu, W K

    2002-01-01

    We have observed a strong non-linear effect in copper cluster ions induced damage in silicon. Copper cluster ions Cu sub n (n=1,2,...,7) were extracted from a source of negative ions by cesium sputtering. P-type silicon wafers were irradiated with copper cluster ions at an atomic dosage range of 8x10 sup 1 sup 2 to 1x10 sup 1 sup 5 atoms/cm sup 2 at the energy of 6 keV/atom. The quantitative characterization of the cluster ion induced damage was performed by Rutherford backscattering spectrometry/channeling analysis. Comparison with analytical overlapping model shows very good agreement.

  18. Selective population of high-j states via heavy-ion-induced transfer reactions

    International Nuclear Information System (INIS)

    Bond, P.D.

    1982-01-01

    One of the early hopes of heavy-ion-induced transfer reactions was to populate states not seen easily or at all by other means. To date, however, I believe it is fair to say that spectroscopic studies of previously unknown states have had, at best, limited success. Despite the early demonstration of selectivity with cluster transfer to high-lying states in light nuclei, the study of heavy-ion-induced transfer reactions has emphasized the reaction mechanism. The value of using two of these reactions for spectroscopy of high spin states is demonstrated: 143 Nd( 16 O, 15 O) 144 Nd and 170 Er( 16 O, 15 Oγ) 171 Er

  19. Effect of implanted species on thermal evolution of ion-induced defects in ZnO

    International Nuclear Information System (INIS)

    Azarov, A. Yu.; Rauwel, P.; Kuznetsov, A. Yu.; Svensson, B. G.; Hallén, A.; Du, X. L.

    2014-01-01

    Implanted atoms can affect the evolution of ion-induced defects in radiation hard materials exhibiting a high dynamic annealing and these processes are poorly understood. Here, we study the thermal evolution of structural defects in wurtzite ZnO samples implanted at room temperature with a wide range of ion species (from 11 B to 209 Bi) to ion doses up to 2 × 10 16  cm −2 . The structural disorder was characterized by a combination of Rutherford backscattering spectrometry, nuclear reaction analysis, and transmission electron microscopy, while secondary ion mass spectrometry was used to monitor the behavior of both the implanted elements and residual impurities, such as Li. The results show that the damage formation and its thermal evolution strongly depend on the ion species. In particular, for F implanted samples, a strong out-diffusion of the implanted ions results in an efficient crystal recovery already at 600 °C, while co-implantation with B (via BF 2 ) ions suppresses both the F out-diffusion and the lattice recovery at such low temperatures. The damage produced by heavy ions (such as Cd, Au, and Bi) exhibits a two-stage annealing behavior where efficient removal of point defects and small defect clusters occurs at temperatures ∼500 °C, while the second stage is characterized by a gradual and partial annealing of extended defects. These defects can persist even after treatment at 900 °C. In contrast, the defects produced by light and medium mass ions (O, B, and Zn) exhibit a more gradual annealing with increasing temperature without distinct stages. In addition, effects of the implanted species may lead to a nontrivial defect evolution during the annealing, with N, Ag, and Er as prime examples. In general, the obtained results are interpreted in terms of formation of different dopant-defect complexes and their thermal stability

  20. Effect of implanted species on thermal evolution of ion-induced defects in ZnO

    Science.gov (United States)

    Azarov, A. Yu.; Hallén, A.; Du, X. L.; Rauwel, P.; Kuznetsov, A. Yu.; Svensson, B. G.

    2014-02-01

    Implanted atoms can affect the evolution of ion-induced defects in radiation hard materials exhibiting a high dynamic annealing and these processes are poorly understood. Here, we study the thermal evolution of structural defects in wurtzite ZnO samples implanted at room temperature with a wide range of ion species (from 11B to 209Bi) to ion doses up to 2 × 1016 cm-2. The structural disorder was characterized by a combination of Rutherford backscattering spectrometry, nuclear reaction analysis, and transmission electron microscopy, while secondary ion mass spectrometry was used to monitor the behavior of both the implanted elements and residual impurities, such as Li. The results show that the damage formation and its thermal evolution strongly depend on the ion species. In particular, for F implanted samples, a strong out-diffusion of the implanted ions results in an efficient crystal recovery already at 600 °C, while co-implantation with B (via BF2) ions suppresses both the F out-diffusion and the lattice recovery at such low temperatures. The damage produced by heavy ions (such as Cd, Au, and Bi) exhibits a two-stage annealing behavior where efficient removal of point defects and small defect clusters occurs at temperatures ˜500 °C, while the second stage is characterized by a gradual and partial annealing of extended defects. These defects can persist even after treatment at 900 °C. In contrast, the defects produced by light and medium mass ions (O, B, and Zn) exhibit a more gradual annealing with increasing temperature without distinct stages. In addition, effects of the implanted species may lead to a nontrivial defect evolution during the annealing, with N, Ag, and Er as prime examples. In general, the obtained results are interpreted in terms of formation of different dopant-defect complexes and their thermal stability.

  1. The structure of the hypothetical protein smu.1377c from Streptococcus mutans suggests a role in tRNA modification

    International Nuclear Information System (INIS)

    Fu, Tian-Min; Liu, Xiang; Li, Lanfen; Su, Xiao-Dong

    2010-01-01

    The crystal structure of smu.1377c, a hypothetical protein from S. mutans, shows a similar fold to Sua5-YciO-YrdC-family proteins and indicates its functional role in tRNA modification. Members of the Sua5-YciO-YrdC protein family are found in both eukaryotes and prokaryotes and possess a conserved α/β twisted open-sheet fold. The Escherichia coli protein YrdC has been shown to be involved in modification of tRNA. The crystal structure of smu.1377c, a hypothetical protein from Streptococcus mutans, has been determined to 2.25 Å resolution. From structure analysis and comparison, it is shown that smu.1377c is a member of the Sua5-YciO-YrdC family and that it may play the same role as E. coli YrdC

  2. Structural modifications of Helicobacter pylori lipopolysaccharide: An idea for how to live in peace

    Science.gov (United States)

    Chmiela, Magdalena; Miszczyk, Eliza; Rudnicka, Karolina

    2014-01-01

    In this review, we discuss the findings and concepts underlying the “persistence mechanisms” of Helicobacter pylori (H. pylori), a spiral-shaped, Gram-negative rod bacterium that was discovered as a gastric pathogen by Marshall and Warren in 1984. H. pylori colonizes the gastric mucosa of nearly half of the human population. Infections appear in early childhood and, if not treated, persist for life. The presence or absence of symptoms and their severity depend on multiple bacterial components, host susceptibility and environmental factors, which allow H. pylori to switch between pathogenicity and commensalism. Many studies have shown that H. pylori components may facilitate the colonization process and the immune response of the host during the course of H. pylori infection. These H. pylori-driven interactions might result from positive or negative modulation. Among the negative immunomodulators, a prominent position is occupied by a vacuolating toxin A (VacA) and cytotoxin-associated gene A (CagA) protein. However, in light of the recent studies that are presented in this review, it is necessary to enrich this panel with H. pylori lipopolysaccharide (LPS). Together with CagA and VacA, LPS suppresses the elimination of H. pylori bacteria from the gastric mucosa by interfering with the activity of innate and adaptive immune cells, diminishing the inflammatory response, and affecting the adaptive T lymphocyte response, thus facilitating the development of chronic infections. The complex strategy of H. pylori bacteria for survival in the gastric mucosa of the host involves both structural modifications of LPS lipid A to diminish its endotoxic properties and the expression and variation of Lewis determinants, arranged in O-specific chains of H. pylori LPS. By mimicking host components, this phenomenon leaves these bacteria “invisible” to immune cells. Together, these mechanisms allow H. pylori to survive and live for many years within their hosts. PMID:25110419

  3. Structural Study and Modification of Support Layer for Forward Osmosis Membranes

    KAUST Repository

    Shi, Meixia

    2016-06-01

    Water scarcity is a serious global issue, due to the increasing population and developing economy, and membrane technology is an essential way to address this problem. Forward osmosis (FO) is an emerging membrane process, due to its low energy consumption (not considering the draw solute regeneration). A bottleneck to advance this technology is the design of the support layer for FO membranes to minimize the internal concentration polarization. In this dissertation, we focus on the structural study and modification of the support layer for FO membranes. Firstly, we digitally reconstruct different membrane morphologies in 3D and propose a method for predicting performance in ultrafiltration operations. Membranes with analogous morphologies are later used as substrate for FO membranes. Secondly, we experimentally apply substrates with different potentially suitable morphologies as an FO support layer. We investigate their FO performance after generating a selective polyamide layer on the top, by interfacial polymerization. Among the different substrates we include standard asymmetric porous membranes prepared from homopolymers, such as polysulfone. Additionally block copolymer membrane and Anodisc alumina membrane are chosen based on their exceptional structures, with cylindrical pores at least in part. 3D digitally reconstructed porous substrates, analogous to those investigated for ultrafiltration, are then used to model the performance in FO operation. Finally, we analyze the effect of intermediate layers between the porous substrate and the interfacial polymerized layer. We investigate two materials including chitosan and hydrogel. The main results are the following. Pore-scale modeling for digital membrane generation effectively predicts the velocity profile in different layers of the membrane and the performance in UF experiments. Flow simulations confirm the advantage of finger-like substrates over sponge-like ones, when high water permeance is sought

  4. Ion-beam induced structure modifications in amorphous germanium; Ionenstrahlinduzierte Strukturmodifikationen in amorphem Germanium

    Energy Technology Data Exchange (ETDEWEB)

    Steinbach, Tobias

    2012-05-03

    Object of the present thesis was the systematic study of ion-beam induced structure modifications in amorphous germanium (a-Ge) layers due to low- (LEI) and high-energetic (SHI) ion irradiation. The LEI irradiation of crystalline Ge (c-Ge) effects because the dominating nuclear scattering of the ions on the solid-state atoms the formation of a homogeneous a-Ge Layer. Directly on the surface for fluences of two orders of magnitude above the amorphization fluence the formation of stable cavities independently on the irradiation conditions was observed. For the first time for the ion-beam induced cavity formation respectively for the steady expansion of the porous layer forming with growing fluence a linear dependence on the energy {epsilon}{sub n} deposed in nuclear processes was detected. Furthermore the formation of buried cavities was observed, which shows a dependence on the type of ions. While in the c-Ge samples in the range of the high electronic energy deposition no radiation defects, cavities, or plastic deformations were observed, the high electronic energy transfer in the 3.1 {mu}m thick pre-amorphized a-Ge surface layers leads to the formation of randomly distributed cavities. Basing on the linear connection between cavity-induced vertical volume expansion and the fluence determined for different energy transfers for the first time a material-specific threshold value of {epsilon}{sub e}{sup HRF}=(10.5{+-}1.0) kev nm{sup -1} was determined, above which the ion-beam induced cavity formation in a-Ge sets on. The anisotropic plastic deformation of th a-Ge layer superposed at inclined SHI irradiation on the cavity formation was very well described by an equation derived from the viscoelastic Maxwell model, but modified under regardment of the experimental results. The positive deformation yields determined thereby exhibit above a threshold value for the ion-beam induced plastic deformation {epsilon}{sub e}{sup S{sub a}}=(12{+-}2) keV nm{sup -1} for the first

  5. Preface: Photon and fast Ion induced Processes in Atoms, MOlecules and Nanostructures (PIPAMON)

    Science.gov (United States)

    Kövér, László

    2016-02-01

    This Special Issue contains selected papers of contributions presented in the International Workshop on Photon and fast Ion induced Processes in Atoms, MOlecules and Nanostructures (PIPAMON), held between March 24 and 26, 2015 in Debrecen, Hungary. The venue, the Aquaticum Thermal and Wellness Hotel provided a pleasant ;all-under-one-roof; environment for the event.

  6. Roughening instability and ion-induced viscous relaxation of SiO2 surfaces

    International Nuclear Information System (INIS)

    Mayer, T.M.; Chason, E.; Howard, A.J.

    1994-01-01

    We characterize the development of nanometer scale topography (roughness) on SiO 2 surfaces as a result of low energy, off-normal ion bombardment, using in situ energy dispersive x-ray reflectivity and atomic force microscopy. Surfaces roughen during sputtering by heavy ions (Xe), with roughness increasing approximately linearly with ion fluence up to 10 17 cm -2 . A highly coherent ripple structure with wavelength of 30 nm and oriented with the wave vector parallel to the direction of incidence is observed after Xe sputtering at 1 keV. Lower frequency, random texture is also observed. Subsequent light ion (H, He) bombardment smoothens preroughened surfaces. The smoothing kinetics are first order with ion fluence and strongly dependent on ion energy in the range 0.2--1 eV. We present a linear model to account for the experimental observations which includes roughening both by random stochastic processes and by development of a periodic surface instability due to sputter yield variations with surface curvature which leads to ripple development. Smoothing occurs via ion bombardment induced viscous flow and surface diffusion. From the smoothing kinetics with H and He irradiation we measure the radiation enhanced viscosity of SiO 2 and find values on the order of 1--20x10 12 N s m -2 . The viscous relaxation per ion scales as the square root of the ion induced displacements in the film over the range of the ion penetration, suggesting short-lived defects with a bimolecular annihilation mechanism. The surface instability mechanism accounts for the ripple formation, while inclusion of stochastic roughening produces the random texture and reproduces the observed linear roughening kinetics and the magnitude of the overall roughness

  7. Changes of Lignin Molecular Structures in a Modification of Kraft Lignin Using Acid Catalyst.

    Science.gov (United States)

    Kim, Sunghoon; Oh, Seungtaek; Lee, Jungmin; Roh, Hyun-Gyoo; Park, Jongshin

    2016-08-05

    The purpose of this study is to modify lignin for better blending with general purpose synthetic polymers. The possible advantages by using this modification would be cost reduction, better physical properties, and biodegradability. In this study, butyrolactone-modified lignin (BLL) and tetrahydrofuran-modified lignin (THFL) were used for aliphatic chain modification of lignin using an acid-catalyzed esterification method in order to mimic the relation of lignin-carbohydrate-complex (LCC) and cellulose. The results of several analyses indicated that lignin was well modified. It was confirmed that the lignin was modified as expected and the reaction sites of the modification, as well as the reaction behaviors, were varied by the reagent types. The result of X-ray diffraction analysis (XRD) analysis indicated that modified lignin/polymer blends increased the crystallinity due to their good compatibility. It can be confirmed that the type of alkyl chain and the miscibility gap between the alkyl chain-matrix affected the mechanical properties enormously in the fungi-degradable environment. From this study, a new method of lignin modification is proposed, and it is found that modified lignin retains the property of the substituted aliphatic chain well. This method could be a proper lignin modification method.

  8. Changes of Lignin Molecular Structures in a Modification of Kraft Lignin Using Acid Catalyst

    Directory of Open Access Journals (Sweden)

    Sunghoon Kim

    2016-08-01

    Full Text Available The purpose of this study is to modify lignin for better blending with general purpose synthetic polymers. The possible advantages by using this modification would be cost reduction, better physical properties, and biodegradability. In this study, butyrolactone-modified lignin (BLL and tetrahydrofuran-modified lignin (THFL were used for aliphatic chain modification of lignin using an acid-catalyzed esterification method in order to mimic the relation of lignin-carbohydrate-complex (LCC and cellulose. The results of several analyses indicated that lignin was well modified. It was confirmed that the lignin was modified as expected and the reaction sites of the modification, as well as the reaction behaviors, were varied by the reagent types. The result of X-ray diffraction analysis (XRD analysis indicated that modified lignin/polymer blends increased the crystallinity due to their good compatibility. It can be confirmed that the type of alkyl chain and the miscibility gap between the alkyl chain-matrix affected the mechanical properties enormously in the fungi-degradable environment. From this study, a new method of lignin modification is proposed, and it is found that modified lignin retains the property of the substituted aliphatic chain well. This method could be a proper lignin modification method.

  9. Vocal Modification Abilities and Brain Structures in Parrots – how do they Correlate?

    DEFF Research Database (Denmark)

    Harpøth, Solveig Walløe

    independent studies where I 1) compare the level of vocal complexity (i.e. modification of the contact call in response to playback stimuli) with the social complexity of four different parrot species, 2) correlate the vocal modification ability of parrots with a brain region involved in vocal learning, i...... comes a need for higher communicative complexity. We compared four different parrot species, (peach-­fronted conure, Aratinga aurea; cockatiel, Nymphicus hollandicus; peach-­faced lovebird, Agapornis roseicollis; budgerigar, Melopsittacus undulatus) with different levels of social complexity. They had...... their vocal modification ability tested through semi-interactive playback experiments. We found that the species with the highest level of social complexity (i.e. peach-­fronted conure) was also the species making the biggest change to the contact call in response to playback stimuli. The budgerigar appears...

  10. Structural modification of aluminium oxynitride phases under stresses at high temperatures, high pressures and under irradiation by fast neutrons

    International Nuclear Information System (INIS)

    Labbe, J.C.; Jeanne, A.; Roult, G.

    1990-01-01

    The structural modifications of the aluminium oxynitride phases under stresses are studied by the time of flight neutron diffraction method, at high temperatures (up to 1375degC), at high pressures (up to 2.4 GPa), and under irradiation by fast neutrons (up to 3.2 X 10 20 n/cm 2 ). In each case the evolutions of cell parameter, interatomic bond angles, bond lengths and atomic positions are given. (orig.)

  11. Modification of ntezi bentonite structure by hydrochloric acid: process kinetics and structural properties of the modified samples

    International Nuclear Information System (INIS)

    Ajemba, R.O.

    2014-01-01

    Bentonite from Ntezi was modified by reacting it with different concentrations of hydrochloric acid solutions. The modified samples were analysed by x-ray fluorescence. The kinetics of the modification reaction was studied by performing the experiment at different temperatures and times. Results of the analysis of the modified samples showed that the octahedral cations were removed which altered the chemical composition of the bentonite. The surface area and adsorptive capacity of the bentonite were improved after the modification. The kinetic studies showed that the acid modification reaction is controlled by the product layer diffusion and can be represented by (1-(l-X)/sup 1/3)/sup 2/ = k t; where, X is the fraction of the bentonite dissolved at time t. The activation energy was determined to be 24.98 kJ/mol. (author)

  12. Protein structural changes in keratin fibers induced by chemical modification using 2-iminothiolane hydrochloride: a Raman spectroscopic investigation.

    Science.gov (United States)

    Kuzuhara, Akio

    2005-11-01

    For the purpose of investigating in detail the influence of chemical modification using 2-iminothiolane hydrochloride (2-IT) on keratin fibers, the structure of cross-sections at various depths of white human hair, treated with 2-IT and then oxidized, was directly analyzed without isolating the cuticle and cortex, using Raman spectroscopy. In particular, the beta-sheet and/or random coil content (beta/R) and the alpha-helix (alpha) content in human hair fibers were estimated by amide I band analysis. The S-S band intensity, amide III (unordered) band intensity, and beta/R content existing from the cuticle region to the center of cortex region of virgin white human hair remarkably increased by performing the chemical modification using 2-IT. On the other hand, not only the S-S band intensity, but also S-O band intensity existing throughout the cortex region of the bleached (damaged) white human hair increased by performing chemical modification using 2-IT. In particular, beta/R content existing throughout the cortex region of the bleached white human hair decreased, while the skeletal C-C stretch (alpha) band intensity at 935 cm(-1) and the alpha content remarkably increased. This indicates a secondary structural change from the random coil form to the alpha-helix form in the proteins existing throughout the cortex region. From these experiments, we concluded that the formation of new disulfide (-SS-) groups resulting from chemical modification using 2-IT induced the secondary structural changes of proteins existing throughout the cortex region. Copyright 2005 Wiley Periodicals, Inc

  13. How modification of accessible lysines to phenylalanine modulates the structural and functional properties of horseradish peroxidase: a simulation study.

    Directory of Open Access Journals (Sweden)

    Leila Navapour

    Full Text Available Horseradish Peroxidase (HRP is one of the most studied peroxidases and a great number of chemical modifications and genetic manipulations have been carried out on its surface accessible residues to improve its stability and catalytic efficiency necessary for biotechnological applications. Most of the stabilized derivatives of HRP reported to date have involved chemical or genetic modifications of three surface-exposed lysines (K174, K232 and K241. In this computational study, we altered these lysines to phenylalanine residues to model those chemical modifications or genetic manipulations in which these positively charged lysines are converted to aromatic hydrophobic residues. Simulation results implied that upon these substitutions, the protein structure becomes less flexible. Stability gains are likely to be achieved due to the increased number of stable hydrogen bonds, improved heme-protein interactions and more integrated proximal Ca2+ binding pocket. We also found a new persistent hydrogen bond between the protein moiety (F174 and the heme prosthetic group as well as two stitching hydrogen bonds between the connecting loops GH and F'F″ in mutated HRP. However, detailed analysis of functionally related structural properties and dynamical features suggests reduced reactivity of the enzyme toward its substrates. Molecular dynamics simulations showed that substitutions narrow the bottle neck entry of peroxide substrate access channel and reduce the surface accessibility of the distal histidine (H42 and heme prosthetic group to the peroxide and aromatic substrates, respectively. Results also demonstrated that the area and volume of the aromatic-substrate binding pocket are significantly decreased upon modifications. Moreover, the hydrophobic patch functioning as a binding site or trap for reducing aromatic substrates is shrunk in mutated enzyme. Together, the results of this simulation study could provide possible structural clues to explain

  14. Study of structural modifications induced by ion implantation in austenitic stainless steel; Etude des modifications structurales induites par implantation ionique dans les aciers austenitiques

    Energy Technology Data Exchange (ETDEWEB)

    Dudognon, J

    2006-12-15

    Ion implantation in steels, although largely used to improve the properties of use, involves structural modifications of the surface layer, which remain still prone to controversies. Within this context, various elements (N, Ar, Cr, Mo, Ag, Xe and Pb) were implanted (with energies varying from 28 to 280 keV) in a 316LVM austenitic stainless steel. The implanted layer has a thickness limited to 80 nm and a maximum implanted element concentration lower than 10 % at. The analysis of the implanted layer by grazing incidence X ray diffraction highlights deformations of austenite lines, appearance of ferrite and amorphization of the layer. Ferritic phase which appears at the grain boundaries, whatever the implanted element, is formed above a given 'threshold' of energy (produced of fluency by the energy of an ion). The formation of ferrite as well as the amorphization of the implanted layer depends only on energy. In order to understand the deformations of austenite diffraction lines, a simulation model of these lines was elaborated. The model correctly describes the observed deformations (broadening, shift, splitting) with the assumption that the expansion of the austenitic lattice is due to the presence of implanted element and is proportional to the element concentration through a coefficient k'. This coefficient only depends on the element and varies linearly with its radius. (author)

  15. Modifications in optical and structural properties of PMMA/PCTFE blend films as a function of PCTFE concentration

    Energy Technology Data Exchange (ETDEWEB)

    Tripathi, J., E-mail: jtripathi00@gmail.com [Dept. of Physics, ISLE, IPS Academy, Indore (India); Sharma, A. [Dept. of Physics, Manipal University Jaipur, Jaipur (India); Tripathi, S. [UGC-DAE Consortium for Scientific Research, Indore (India); Bisen, R. [Dept. of Physics, ISLE, IPS Academy, Indore (India); Agrawal, A. [Dept. of Elect. and Commun., Global Engineering College, Jabalpur (India)

    2017-06-15

    The poly (methyl methacrylate) (PMMA) polymer blend films were prepared by solution casting method with varying PolyChloroTriFluoroEthylene (PCTFE) concentrations (1–5 wt %). The crystallinity, bonding behavior and disorder in the films were investigated with X-ray diffraction (XRD), Fourier transform infrared (FTIR), UV–visible and ellipsometry techniques, while surface morphology was studied using Atomic force microscopy (AFM). The nanocrystalline nature of PMMA is seen to be preserved in the blends although there are clear indications of bond modifications. The addition of PCTFE results in the improvement of overall crystallinity of the films via the interaction among PMMA and degraded PCTFE molecules when the films are casted from diluted solutions. In agreement, corresponding disorder in terms of Urbach energy shows a decreasing trend upon inclusion of more and more PCTFE molecules. Micro-Raman spectra are dominated by fluorescence background, which is proposed as arising from degraded PCTFE. Supporting this, FTIR spectra also shows modifications in bonding as a function of PCTFE percentage, but this bond modification is not enough to produce refractive index variation in the sample, which is dominated by the host PMMA contribution for all the PCTFE concentrations. The study suggests the useful range of PCTFE concentration in which PMMA host properties can be modified for optimizing optical and structural properties without much degradation of PCTFE. - Highlights: • PMMA blend films with varying PCTFE concentrations (1–5 wt%) were prepared. • Nanocrystalline nature of PMMA is preserved in spite of bond modifications. • Addition of PCTFE results in improvement of overall crystallinity of the films. • Urbach energy shows a decreasing Disorder upon inclusion of more PCTFE molecules. • FTIR spectra show bond modifications without changing refractive index.

  16. Molecular modification of native coffee polysaccharide using subcritical water treatment: Structural characterization, antioxidant, and DNA protecting activities.

    Science.gov (United States)

    Getachew, Adane Tilahun; Chun, Byung Soo

    2017-06-01

    Polysaccharides are an abundant resource in coffee beans and have proved to show numerous bioactivities. Despite their abundance, their activities are not always satisfactory mostly due to their structure and large molecular size. Molecular modifications of native polysaccharides can overcome this problem. In this study, we used a novel and green method to modify native coffee polysaccharides using subcritical water (SCW) treatment. The SCW treatment was used at the temperature of 180°C-220°C and pressure of 30-60bar. The molecular and structural modification of the polysaccharides was confirmed using several techniques such as FT-IR, UV spectroscopy, XRD, and TGA. The antioxidant activity of the modified polysaccharides was evaluated using several chemical and Saccharomyces cerevisiae-based high throughput assays. The modified polysaccharides showed high antioxidant activities in all tested assays. Moreover, the polysaccharides showed high DNA protection activities. Therefore, SCW could be employed as a green solvent for molecular modification of polysaccharides. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Heavy ion induced genetic effects in mammalian cells. Final report

    International Nuclear Information System (INIS)

    Kiefer, J.; Brend'amour, M.; Casares, A.; Egenolf, R.; Gutermuth, F.; Ikpeme, S.E.; Koch, S.; Kost, M.; Loebrich, M.; Pross, H.D.; Russmann, C.; Schmidt, P.; Schneider, E.; Stoll, U.; Weber, K.J.

    2001-01-01

    DNA double-strand breaks (DSBs) are generally assumed to be the most relevant initial event producing radiation-induced cellular lethality, as well as mutations and transformations. The dependence of their formation on radiation quality has been recently reviewed. Contrary to earlier observations there seems to be now agreement that the RBE does not increase above unity with increasing LET in mammalian cells when conventional techniques are applied which are not able to resolve smaller fragments. If they are, however, included in the analysis maximum RBE values around 2 are obtained. The situation is different with yeast: An increased effectiveness for DSB induction has been reported with alpha particles, as well as for heavy ions. This may be due to differences in methods or to chromosomal structure, as discussed in more detail in this paper. DSB induction was measured for a LET range of 100 to 11500 keV/? m in yeast cells using pulsed field gel electrophoresis. Under the conditions applied the chromosomes of the yeast cells could be separated according to size allowing the direct quantification of the DSB yield by measuring the intensity of the largest chromosomes. The results demonstrate clearly that DSB induction in yeast depends on radiation quality. The derived cross-sections for DSB induction were also compared to those for cell inactivation determined in parallel experiments under identical irradiation conditions. (orig.)

  18. Chemical modification and structural analysis of protein isolates to produce hydrogel using Whitemouth croaker (Micropogonias furnieri) wastes.

    Science.gov (United States)

    Martins, Vilásia Guimarães; Costa, Jorge Alberto Vieira; Damodaran, Srinivasan; Prentice, Carlos

    2011-09-01

    Recovery and alteration of fish protein from wastes and its use has been regarded as a promising alternative to develop useful products once polymer gels have a high capacity of water uptake. This study aims to produce hydrogel, a super absorbent biopolymer from modified fish protein, in order to evaluate the protein structure. In the modified proteins, analyses of the extent of modification of the lysine residues, electrophoresis, and electrometric titration were performed. In the hydrogels were realized assays of swelling water. The proteins with more modifications were shown as 63.5% and 75.9% of lysine residues, from fish protein isolate obtained with alkaline and acid solubilization, respectively. The modified protein in that same rate presented 332.0 and 311.4 carboxyl groups. Accordingly, the hydrogel produced from alkaline and acid isolates reached a maximum water uptake in 24 h of 79.42 and 103.25 g(water)/g(dry gel), respectively.

  19. Changes in Structural-Mechanical Properties and Degradability of Collagen during Aging-associated Modifications.

    Science.gov (United States)

    Panwar, Preety; Lamour, Guillaume; Mackenzie, Neil C W; Yang, Heejae; Ko, Frank; Li, Hongbin; Brömme, Dieter

    2015-09-18

    During aging, changes occur in the collagen network that contribute to various pathological phenotypes in the skeletal, vascular, and pulmonary systems. The aim of this study was to investigate the consequences of age-related modifications on the mechanical stability and in vitro proteolytic degradation of type I collagen. Analyzing mouse tail and bovine bone collagen, we found that collagen at both fibril and fiber levels varies in rigidity and Young's modulus due to different physiological changes, which correlate with changes in cathepsin K (CatK)-mediated degradation. A decreased susceptibility to CatK-mediated hydrolysis of fibrillar collagen was observed following mineralization and advanced glycation end product-associated modification. However, aging of bone increased CatK-mediated osteoclastic resorption by ∼27%, and negligible resorption was observed when osteoclasts were cultured on mineral-deficient bone. We observed significant differences in the excavations generated by osteoclasts and C-terminal telopeptide release during bone resorption under distinct conditions. Our data indicate that modification of collagen compromises its biomechanical integrity and affects CatK-mediated degradation both in bone and tissue, thus contributing to our understanding of extracellular matrix aging. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  20. Influence of Modification and Casting Technology on Structure of IN-713C Superalloy Castings

    Directory of Open Access Journals (Sweden)

    Binczyk F.

    2016-09-01

    Full Text Available The paper presents the results concerning impact of modification (volume and surface techniques, pouring temperature and mould temperature on stereological parameters of macrostructure in IN713C castings made using post-production scrap. The ability to adjust the grain size is one of the main issues in the manufacturing of different nickel superalloy castings used in aircraft engines. By increasing the grain size one can increase the mechanical properties, like diffusion creep resistance, in higher temperatures. The fine grained castings. on the other hand, have higher mechanical properties in lower temperatures and higher resistance to thermal fatigue. The test moulds used in this study, supplied by Pratt and Whitney Rzeszow, are ordinarily used to cast the samples for tensile stress testing. Volume modification was carried out using the patented filter containing cobalt aluminate. The macrostructure was described using the number of grains per mm2, mean grain surface area and shape index. Obtained results show strong relationship between the modification technique, pouring temperature and grain size. There was no significant impact of mould temperature on macrostructure.

  1. Chemical modifications in polyethylene terephthalate films induced by 35 MeV/u Ar ions

    International Nuclear Information System (INIS)

    Liu Changlong; Zhu Zhiyong; Jin Yunfan; Sun Youmei; Hou Mingdong; Wang Zhiguang; Chen Xiaoxi; Zhang Chonghong; Liu Jie; Li Baoquan; Wang Yanbin

    2000-01-01

    Semicrystalline polyethylene terephthalate (PET) foil stacks were irradiated under vacuum and at room temperature with 35 MeV/u Ar ions to fluences ranging from 1x10 10 to 5x10 12 ions/cm 2 . Ion induced modifications in crystalline and chemical structures were studied by means of differential scanning calorimetry (DSC), Fourier-transform infrared absorption spectroscopy (FTIR), and X-ray diffractometer (XRD). The DSC and XRD data show a significant loss of crystallinity at the absorbed doses higher than 4.0 MGy. FTIR measurements indicate that the loss of crystallinity of the irradiated PET is related to the scission processes of the main chains at the trans configuration of the ethylene glycol residue. Meanwhile, at the absorbed dose above about 4.0 MGy, bond breaking processes at the para position of benzene are also observed. The benzene ring structures are found to be more stable under irradiation

  2. A large area position-sensitive ionization chamber for heavy-ion-induced reaction studies

    CERN Document Server

    Pant, L M; Dinesh, B V; Thomas, R G; Saxena, A; Sawant, Y S; Choudhury, R K

    2002-01-01

    A large area position-sensitive ionization chamber with a wide dynamic range has been developed to measure the mass, charge and energy of the heavy ions and the fission fragments produced in heavy-ion-induced reactions. The split anode geometry of the detector makes it suitable for both particle identification and energy measurements for heavy ions and fission fragments. The detector has been tested with alpha particles from sup 2 sup 4 sup 1 Am- sup 2 sup 3 sup 9 Pu source, fission fragments from sup 2 sup 5 sup 2 Cf and the heavy-ion beams from the 14UD Mumbai Pelletron accelerator facility. Using this detector, measurements on mass and total kinetic energy distributions in heavy-ion-induced fusion-fission reactions have been carried out for a wide range of excitation energies. Results on deep inelastic collisions and mass-energy correlations on different systems using this detector setup are discussed.

  3. Using the thermal diffusion cloud chamber to study the ion-induced nucleation by radon decay

    International Nuclear Information System (INIS)

    Wu, Yefei.

    1991-01-01

    Thermal diffusion cloud chamber is steady-state device and has been extensively used for nucleation research. In order to study the ion-induced nucleation by radon decay, a new chamber was designed with improved both upper and bottom plates, the system of circulating fluid, the gasketting, the temperature measurement and the insulation. An alternative method of using oxygen as carrier gas was examined. Therefore, the heavy carrier gas including nitrogen, oxygen, neon, argon and air can be used to study radon radiolysis-induced nucleation for the water or organic compounds in the TDCC. The effects of the pressure and temperature ranges on the density, supersaturation, temperature and partial pressure profile for the water-oxygen-helium in the TDCC have been examined. Based on the classical theory, the rate profile of ion-induced nucleation by radon decays was calculated and compared with the homogeneous nucleation. From measured indoor concentrations of Volatile Organic Compounds (VOC), thermodynamic theory models were used to assess the possibility that these compounds will form ultrafine particles in indoor air by ion-induced nucleation. The energy, number of molecules and equilibrium radius of clusters have been calculated based on Such and Thomson theories. These two sets of values have been compared. Ion cluster radii corresponding to 1--3 VOC molecules are in range of 3--5 x 10 -8 cm. 43 refs., 18 figs., 5 tabs

  4. Modification of graphite structure by irradiation, revealed by thermal oxidation. Examination by electronic microscopy

    International Nuclear Information System (INIS)

    Rouaud, Michel

    1969-01-01

    Based on the analysis of images obtained by electronic microscopy, this document reports the comparative study of the action of neutrons on three different graphites: a natural one (Ticonderoga) and two pyrolytic ones (Carbone-Lorraine and Raytheon). The approach is based on the modification of features of thermal oxidation of graphites by dry air after irradiation. Different corrosion features are identified. The author states that there seems to be a relationship between the number and shape of these features, and defects existing on the irradiated graphite before oxidation. For low doses, the feature aspect varies with depth at which oxidation occurs. For higher doses, the aspect remains the same [fr

  5. Nascent stages of DNA radiolysis: secondary electron and reactive ion induced damage

    International Nuclear Information System (INIS)

    Huels, M.A.

    2000-01-01

    Full text: It is by now well understood that most of the energy deposited in solids by ionizing radiation is converted within less than attoseconds into the production of ions, radicals, and ballistic low-energy secondary electrons. The latter are known to decompose small molecules even at electron energies well below molecular ionization thresholds regardless of molecular aggregation state, and have recently been shown to induce substantial yields of single and double strand breaks in supercoiled DNA. In that study, we found that the electron-energy dependent strand break yields have a strong maximum near 10 eV, which was attributed to the decomposition of transient molecular anion (TMA) states, i.e. resonances. The localization of these resonances on the different components of DNA leads to dissociations into anion and radical fragments within femtoseconds, where subsequent fragment reactions on similar timescales are thought to lead to the final observed DNA damage. In order to unravel this sequence of secondary electron and reactive ion induced events, and to better understand their fundamental reaction pathways, we have performed, and will present: (a) measurements of the basic mechanisms by which low-energy (0-30 eV) electrons induce damage to different components of DNA, e.g. H 2 0, deoxyribose analogs, bases, as well as other organic model systems, and (b) measurements of the basic reaction pathways by which some of the energetic ion fragments observed in (a) induce further damage in simple hydrocarbon films, as well as solids of DNA components, or their structural analogs. Our experiments show that: (i) for electron energies below 15 eV dissociative electron attachment (i.e. resonances) results in exocyclic and complex endocyclic bond cleavages in any of the molecular systems studied, leading to the formation of a vast variety of reactive radical and anion fragments, whereas above 15 eV electronic excitations and ionizations (nonresonant mechanisms) may

  6. Likelihood-based modification of experimental crystal structure electron density maps

    Science.gov (United States)

    Terwilliger, Thomas C [Sante Fe, NM

    2005-04-16

    A maximum-likelihood method for improves an electron density map of an experimental crystal structure. A likelihood of a set of structure factors {F.sub.h } is formed for the experimental crystal structure as (1) the likelihood of having obtained an observed set of structure factors {F.sub.h.sup.OBS } if structure factor set {F.sub.h } was correct, and (2) the likelihood that an electron density map resulting from {F.sub.h } is consistent with selected prior knowledge about the experimental crystal structure. The set of structure factors {F.sub.h } is then adjusted to maximize the likelihood of {F.sub.h } for the experimental crystal structure. An improved electron density map is constructed with the maximized structure factors.

  7. Low energy oxygen ion beam modification of the surface morphology and chemical structure of polyurethane fibers

    International Nuclear Information System (INIS)

    Wong, K.H.; Zinke-Allmang, M.; Wan, W.K.; Zhang, J.Z.; Hu, P.

    2006-01-01

    Energetic O + ions were implanted into polyurethane (PU) fiber filaments, at 60 and 100 keV with doses of 5 x 10 14 and 1 x 10 15 ions/cm 2 , to modify the near-surface fiber morphology. The implantations were performed at room temperature and at -197 deg. C, a temperature well below the glass transition temperature for this system. At room temperature, the lower energy implantation heats the fibers primarily near their surface, causing the fiber surface to smoothen and to develop a flattened shape. At the higher energy, the ion beam deposits its energy closer to the fiber core, heating the fiber more uniformly and causing them to re-solidify slowly. This favors a cylindrical equilibrium shape with a smooth fiber surface and no crack lines. The average fiber diameter reduced during 100 keV implantation from 3.1 to 2.3 μm. At -197 deg. C, the ion implantation does not provide enough heat to cause notable physical modifications, but the fibers crack and break during subsequent warming to room temperature. The dose dependence of the crack formation along the fiber intersections is presented. The ion beams further cause near-surface chemical modifications in the fibers, particularly introducing two new chemical functional groups (C-(C=O)-C and C-N-C)

  8. Analysis of Potential Structural Design modifications for the Tail Section of the RAH-66 Comanche Helicopter

    National Research Council Canada - National Science Library

    Tobin, Vincent

    1997-01-01

    .... Structural configurations of the tailcone that meet radar cross-section requirements tend to lack sufficient structural stiffness due to the presence of Kevlar in place of graphite on the outer mold line...

  9. Analysis of Potential Structural Design Modifications for the Tail Section of the RAH-66 Comanche Helicopter

    National Research Council Canada - National Science Library

    Tobin, Vincent

    1997-01-01

    .... Structural configurations of the tailcone that meet radar cross-section requirements tend to lack sufficient structural stiffness due to the presence of Kevlar in place of graphite on the outer mold line...

  10. Structural characteristics of anabolic androgenic steroids contributing to binding to the androgen receptor and to their anabolic and androgenic activities. Applied modifications in the steroidal structure.

    Science.gov (United States)

    Fragkaki, A G; Angelis, Y S; Koupparis, M; Tsantili-Kakoulidou, A; Kokotos, G; Georgakopoulos, C

    2009-02-01

    Anabolic androgenic steroids (AAS) are synthetic derivatives of testosterone introduced for therapeutic purposes providing enhanced anabolic potency with reduced androgenic effects. Androgens mediate their action through their binding to the androgen receptor (AR) which is mainly expressed in androgen target tissues, such as the prostate, skeletal muscle, liver and central nervous system. This paper reviews some of the wide spectrum of testosterone and synthetic AAS structure modifications related to the intended enhancement in anabolic activity. The structural features of steroids necessary for effective binding to the AR and those which contribute to the stipulation of the androgenic and anabolic activities are also presented.

  11. Residue Modification and Mass Spectrometry for the Investigation of Structural and Metalation Properties of Metallothionein and Cysteine-Rich Proteins.

    Science.gov (United States)

    Irvine, Gordon W; Stillman, Martin J

    2017-04-26

    Structural information regarding metallothioneins (MTs) has been hard to come by due to its highly dynamic nature in the absence of metal-thiolate cluster formation and crystallization difficulties. Thus, typical spectroscopic methods for structural determination are limited in their usefulness when applied to MTs. Mass spectrometric methods have revolutionized our understanding of protein dynamics, structure, and folding. Recently, advances have been made in residue modification mass spectrometry in order to probe the hard-to-characterize structure of apo- and partially metalated MTs. By using different cysteine specific alkylation reagents, time dependent electrospray ionization mass spectrometry (ESI-MS), and step-wise "snapshot" ESI-MS, we are beginning to understand the dynamics of the conformers of apo-MT and related species. In this review we highlight recent papers that use these and similar techniques for structure elucidation and attempt to explain in a concise manner the data interpretations of these complex methods. We expect increasing resolution in our picture of the structural conformations of metal-free MTs as these techniques are more widely adopted and combined with other promising tools for structural elucidation.

  12. Study of structural modification of sugarcane bagasse employing hydrothermal treatment followed by atmospheric pressure plasmas treatment

    Science.gov (United States)

    Amorim, Jayr; Pimenta, Maria Teresa; Gurgel, Leandro; Squina, Fabio; Souza-Correa, Jorge; Curvelo, Antonio

    2009-10-01

    Nowadays, the cellulosic ethanol is an important alternative way to many liquid biofuels using renewable biomass rich in polysaccharides. To be used as feedstock for ethanol production, the bagasse needs to be pretreated in order to expose its main constitutive. The present work proposes the use of different pretreatment processes to better expose the cellulose for hydrolysis and fermentation. In the present paper the sugarcane bagasse was submitted to a hydrothermal pretreatment followed by atmospheric pressure plasmas (APPs). An RF microplasma torch was employed as APPs in Ar and Ar/O2 mixing. The bagasse was treated in discharge and post-discharge regions. The position and time of treatment was varied as well as the gas mixture. The quantity of polysaccharides was determined by using high performance liquid chromatography. It was observed the release of a fraction of the hemicelluloses in the sugarcane bagasse. Modifications in the surface of the sugarcane fibers were monitored by employing scanning electron microscopy.

  13. Laser-induced modification of structure and shape of cartilage in otolaryngology and orthopaedics

    Science.gov (United States)

    Sobol’, E. N.; Baum, O. I.; Omel’chenko, A. I.; Soshnikova, Yu. M.; Yuzhakov, A. V.; Kas’yanenko, E. M.; Tokareva, A. V.; Baskov, A. V.; Svistushkin, V. M.; Selezneva, L. V.; Shekhter, A. B.

    2017-11-01

    We present the results of basic research in laser modification of tissues in otolaryngology (correcting the shape of nasal septum and larynx cartilages), cosmetology (correcting ear and nose shape), orthopaedics and spinal surgery (treatment of diseases of spine disc and joints). The physical processes and mechanisms of laser-induced relaxation of stresses and regeneration of tissues are considered. New results of studies in this fast-developing field of laser surgery are presented, in particular, the results of laser correction of costal cartilage shape in the process of making implants for the treatment of larynx stenosis and controlled regeneration of the hyaline articular cartilage. Presented at the Fundamentals of Laser Assisted Micro- and Nanotechnologies (FLAMN-2016) International Symposium (Pushkin, Leningrad oblast, 27 June to 1 July 2016).

  14. Kozloduy Nuclear Power Plant (Unit 1 and 2). Proposed modifications to increase the seismic capability of equipment and main structures

    International Nuclear Information System (INIS)

    Ordonez Villalobos, A.; Monette, P.R.

    1993-01-01

    Within the framework of the European Community's PHARE Programme of improvement to facilities, their operating systems, equipment and buildings of the Kozloduy NPP in Bulgaria, plant safety during seismic events is considered to be an issue of overriding importance, especially in view of the earthquakes the region suffered during the last decade. Westinghouse Energy Systems International (WESI) and Empresarios Agrupados (EA) have initiated an intensive programme for physical upgrading of equipment with a view to augmenting its seismic capability and, at the same time, to studying design modifications in the diesel-generator buildings, pump house and main building structures (turbines, electrical building). The implementation of these modifications requires an in situ inspection of the real conditions of the various elements, analyses, conceptual design and detail engineering, all of which has to be done in short periods of time using resources available at the plant. This activity is performed by the companies mentioned above, with the collaboration of two engineering companies, Energoproekt of Bulgaria and INITEC of Spain. This paper describes the activities developed and the treatment given to the various aspects of improvement of the seismic capability of equipment and structures. (author)

  15. Season-specific and guild-specific effects of anthropogenic landscape modification on metacommunity structure of tropical bats.

    Science.gov (United States)

    Cisneros, Laura M; Fagan, Matthew E; Willig, Michael R

    2015-03-01

    Fragmentation per se due to human land conversion is a landscape-scale phenomenon. Accordingly, assessment of distributional patterns across a suite of potentially connected communities (i.e. metacommunity structure) is an appropriate approach for understanding the effects of landscape modification and complements the plethora of fragmentation studies that have focused on local community structure. To date, metacommunity structure within human-modified landscapes has been assessed with regard to nestedness along species richness gradients. This is problematic because there is little support that species richness gradients are associated with the factors moulding species distributions. More importantly, many alternative patterns are possible, and different patterns may manifest during different seasons and for different guilds because of variation in resource availability and resource requirements of taxa. We determined the best-fit metacommunity structure of a phyllostomid bat assemblage, frugivore ensemble, and gleaning animalivore ensemble within a human-modified landscape in the Caribbean lowlands of Costa Rica during the dry and wet seasons to elucidate important structuring mechanisms. Furthermore, we identified the landscape characteristics associated with the latent gradient underlying metacommunity structure. We discriminated among multiple metacommunity structures by assessing coherence, range turnover, and boundary clumping of an ordinated site-by-species matrix. We identified the landscape characteristics associated with the latent gradient underlying metacommunity structure via hierarchical partitioning. Metacommunity structure was never nested nor structured along a richness gradient. The phyllostomid assemblage and frugivore ensemble exhibited Gleasonian structure (range turnover along a common gradient) during the dry season and Clementsian structure (range turnover and shared boundaries along a common gradient) during the wet season. Distance

  16. Synthesis of lysozyme-metallacarborane conjugates and the effect of boron cluster modification on protein structure and function.

    Science.gov (United States)

    Kowalski, Konrad; Goszczyński, Tomasz; Leśnikowski, Zbigniew J; Boratyński, Janusz

    2015-02-09

    Two complementary methods, "in solution" and "in solid state", for the synthesis of lysozyme modified with metallacarborane (cobalt bis(dicarbollide), Co(C2 B9 H11 )2 (2-) ) were developed. As metallacarborane donors, oxonium adducts of cobalt bis(dicarbollide) and 1,4-dioxane or tetrahydropyran were used. The physicochemical and biochemical properties of the obtained lysozyme-metallacarborane conjugates were studied for changes in secondary and tertiary structure, aggregation behavior, and biological activity. Only minor changes in primary, secondary, and tertiary protein structure were observed, caused by the single substitution of metallacarborane on lysozyme. However, the modification produced significant changes in lysozyme enzymatic activity and a tendency toward time- and temperature-dependent aggregation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Finite element prediction of seismic response modification of monumental structures utilizing base isolation

    Science.gov (United States)

    Spanos, Konstantinos; Anifantis, Nikolaos; Kakavas, Panayiotis

    2015-05-01

    The analysis of the mechanical behavior of ancient structures is an essential engineering task concerning the preservation of architectural heritage. As many monuments of classical antiquity are located in regions of earthquake activity, the safety assessment of these structures, as well as the selection of possible restoration interventions, requires numerical models capable of correctly representing their seismic response. The work presented herein was part of a research project in which a better understanding of the dynamics of classical column-architrave structures was sought by means of numerical techniques. In this paper, the seismic behavior of ancient monumental structures with multi-drum classical columns is investigated. In particular, the column-architrave classical structure under strong ground excitations was represented by a finite element method. This approach simulates the individual rock blocks as distinct rigid blocks interconnected with slidelines and incorporates seismic isolation dampers under the basement of the structure. Sliding and rocking motions of individual stone blocks and drums are modeled utilizing non-linear frictional contact conditions. The seismic isolation is modeled through the application of pad bearings under the basement of the structure. These pads are interpreted by appropriate rubber and steel layers. Time domain analyses were performed, considering the geometric and material non-linear behavior at the joints and the characteristics of pad bearings. The deformation and failure modes of drum columns subject to seismic excitations of various types and intensities were analyzed. The adverse influence of drum imperfections on structural safety was also examined.

  18. Structural modification and band gap engineering of sol–gel dip

    Indian Academy of Sciences (India)

    In the present study, we investigated the effect of vacuum annealing on the structural and optical properties of sol–gel dip-coated thin films of Zn 0.75 Mg 0.25 O alloy. XRD studies revealed that all these films werepolycrystalline with hexagonal wurtzite structure and there was no trace of additional phases other than ZnO.

  19. Structural modification and band gap engineering of sol–gel dip ...

    Indian Academy of Sciences (India)

    In the present study, we investigated the effect of vacuum annealing on the structural and optical properties of sol–gel dip-coated thin films of Zn 0.75 Mg 0.25 O alloy. XRD studies revealed that all these films werepolycrystalline with hexagonal wurtzite structure and there was no trace of additional phases other than ZnO.

  20. Early cytoskeletal protein modifications precede overt structural degeneration in the DBA/2J mouse model of glaucoma

    Directory of Open Access Journals (Sweden)

    Gina Nicole Wilson

    2016-11-01

    Full Text Available Axonal transport deficits precede structural loss in glaucoma and other neurodegenerations. Impairments in structural support, including modified cytoskeletal proteins and microtubule-destabilizing elements, could be initiating factors in glaucoma pathogenesis. We investigated the time course of changes in protein levels and post-translational modifications in the DBA/2J mouse model of glaucoma. Using anterograde tract tracing of the retinal projection, we assessed major cytoskeletal and transported elements as a function of transport integrity in different stages of pathological progression. Using capillary-based electrophoresis, single- and multiplex immunosorbent assays, and immunofluorescence, we quantified hyperphosphorylated neurofilament-heavy chain, phosphorylated tau (ptau, calpain-mediated spectrin breakdown product (145/150kDa, β –tubulin, and amyloid-β42 proteins based on age and transport outcome to the superior colliculus (SC, the main retinal target in mice. Phosphorylated neurofilament-heavy chain (pNF-H was elevated within the optic nerve (ON and SC of 8-10 month-old DBA/2J mice, but was not evident in the retina until 12-15 months, suggesting that cytoskeletal modifications first appear in the distal retinal projection. As expected, higher pNF-H levels in the SC and retina were correlated with axonal transport deficits. Elevations in hyperphosphorylated tau (ptau occurred in ON and SC between 3-8 month of age while retinal ptau accumulations occurred at 12-15 months in DBA/2J mice. In vitro co-immunoprecipitation experiments suggested increased affinity of ptau for the retrograde motor complex protein, dynactin. We observed a transport-related decrease of β-tubulin in ON of 10-12 month-old DBA/2J mice, suggesting destabilized microtubule array. Elevations in calpain-mediated spectrin breakdown product were seen in ON and SC at the earliest age examined, well before axonal transport loss is evident. Finally, transport

  1. Efficient red luminescence from organic-soluble Au25 clusters by ligand structure modification

    Science.gov (United States)

    Mathew, Ammu; Varghese, Elizabeth; Choudhury, Susobhan; Pal, Samir Kumar; Pradeep, T.

    2015-08-01

    An efficient method to enhance visible luminescence in a visibly non-luminescent organic-soluble 4-(tert butyl)benzyl mercaptan (SBB)-stabilized Au25 cluster has been developed. This method relies mainly on enhancing the surface charge density on the cluster by creating an additional shell of thiolate on the cluster surface, which enhances visible luminescence. The viability of this method has been demonstrated by imparting red luminescence to various ligand-protected quantum clusters (QCs), observable to the naked eye. The bright red luminescent material derived from Au25SBB18 clusters was characterized using UV-vis and luminescence spectroscopy, TEM, SEM/EDS, XPS, TG, ESI and MALDI mass spectrometry, which collectively proposed an uncommon molecular formula of Au29SBB24S, suggested to be due to different stapler motifs protecting the Au25 core. The critical role of temperature on the emergence of luminescence in QCs has been studied. The restoration of the surface ligand shell on the Au25 cluster and subsequent physicochemical modification to the cluster were probed by various mass spectral and spectroscopic techniques. Our results provide fundamental insights into the ligand characteristics determining luminescence in QCs.An efficient method to enhance visible luminescence in a visibly non-luminescent organic-soluble 4-(tert butyl)benzyl mercaptan (SBB)-stabilized Au25 cluster has been developed. This method relies mainly on enhancing the surface charge density on the cluster by creating an additional shell of thiolate on the cluster surface, which enhances visible luminescence. The viability of this method has been demonstrated by imparting red luminescence to various ligand-protected quantum clusters (QCs), observable to the naked eye. The bright red luminescent material derived from Au25SBB18 clusters was characterized using UV-vis and luminescence spectroscopy, TEM, SEM/EDS, XPS, TG, ESI and MALDI mass spectrometry, which collectively proposed an uncommon

  2. Electrochemically active manganese oxides: structural modelling, modifications induced by thermal processing and photon insertion

    International Nuclear Information System (INIS)

    Ripert, Michel

    1990-01-01

    The objective of this research study is to understand the mechanism of proton insertion into manganese dioxide. It comprised the performances of in situ discharges of two commercial samples in an electrochemical cell designed for this purpose. In order to characterise the structure of electrochemically active manganese dioxides, and particularly to elucidate the orthorhombic-hexagonal dilemma, the author proposes a crystalline-chemical approach which comprises the development of a unique structural model which takes the structure of all forms of electrochemically active manganese dioxides into account, and a numerical simulation of diffraction diagrams (X rays and neutrons) of these structures. The development of this modelling results in the development of a method which allows, from experimental diffraction diagrams, characteristic structural parameters of each sample of EMD (electrolytic manganese dioxide) or CMD (chemical manganese dioxide) to be obtained. Moreover, the observation of the structural evolution of the dioxide is possible by using in situ neutron diffraction. Reduction has been studied by using slow potential scanning voltammetry. By using these both techniques (neutron diffraction and voltammetry), it is possible to explain the structural mechanism of reduction of MnO 2 and to show the origin of the non-reversibility of the proton/MnO 2 system, to quantitatively explain the shape voltammetry curves, and to highlight experimentally for the first time the different sites of insertion of the proton

  3. Laser structuring and modification of polymer surfaces for chemical and medical microcomponents

    Science.gov (United States)

    Bremus-Koebberling, Elke A.; Meier-Mahlo, Ulrike; Henkenjohann, Oliver; Beckemper, Stefan; Gillner, Arnold

    2004-10-01

    In the production of micro devices the surface properties become more and more important for chemistry, biotechnology and medical technology with respect to wetting properties and chemical composition of the surface. Typical applications are implants as well as micro fluidic systems or miniaturized devices for DNA- and proteome analysis (biochips). In this paper newly designed laser technologies based on UV-laser treatment of polymers for surface processing are described to manipulate wetting properties, cell growth and immobilization of functional molecules with high spatial resolution. Depending on the processing parameters and used polymers either hydrophobic or hydrophilic properties can be enhanced (i.e. laser induced lotus/anti-lotus effect). Enhanced roughness and changes of the chemical composition have also influence on cell growth on polymer surfaces. Thus guiding aids for cells e.g. on medical implants can be generated by laser irradiation. Due to photo oxidation processes while UV-treatment in air, functional groups are created that are suited for covalent bonding of (bio)moelcules onto the surfaces. A second process for the locally selective immobilization of anchor molecules based on azide functionalized templates suitable for further modification steps is presented by means of irradiating polymers under solutions of these linkers.

  4. Modification of DNA radiolysis by DNA-binding proteins: Structural aspects

    International Nuclear Information System (INIS)

    Davidkova, M.; Stisova, V.; Goffinont, S.; Gillard, N.; Castaing, B.; Spotheim-Maurizot, M.

    2006-01-01

    Formation of specific complexes between proteins and their cognate DNA modulates the yields and the location of radiation damage on both partners of the complex. The radiolysis of DNA-protein complexes is studied for: (1) the Escherichia coli lactose operator-repressor complex, (2) the complex between DNA bearing an analogue of an abasic site and the repair protein Fpg of Lactococcus lactis. Experimental patterns of DNA damages are presented and compared to predicted damage distribution obtained using an improved version of the stochastic model RADACK. The same method is used for predicting the location of damages on the proteins. At doses lower than a threshold that depends on the system, proteins protect their specific binding site on DNA while at high doses, the studied complexes are disrupted mainly through protein damage. The loss of binding ability is the functional consequence of the amino-acids modification by OH . radicals. Many of the most probably damaged amino acids are essential for the DNA-protein interaction and within a complex are protected by DNA. (authors)

  5. Hypochlorite-induced structural modifications enhance the chaperone activity of human α2-macroglobulin.

    Science.gov (United States)

    Wyatt, Amy R; Kumita, Janet R; Mifsud, Richard W; Gooden, Cherrie A; Wilson, Mark R; Dobson, Christopher M

    2014-05-20

    Hypochlorite, an oxidant generated in vivo by the innate immune system, kills invading pathogens largely by inducing the misfolding of microbial proteins. Concomitantly, the nonspecific activity of hypochlorite also damages host proteins, and the accumulation of damaged (misfolded) proteins is implicated in the pathology of a variety of debilitating human disorders (e.g., Alzheimer's disease, atherosclerosis, and arthritis). It is well-known that cells respond to oxidative stress by up-regulating proteostasis machinery, but the direct activation of mammalian chaperones by hypochlorite has not, to our knowledge, been previously reported. In this study, we show that hypochlorite-induced modifications of human α2-macroglobulin (α2M) markedly increase its chaperone activity by generating species, particularly dimers formed by dissociation of the native tetramer, which have enhanced surface hydrophobicity. Moreover, dimeric α2M is generated in whole-blood plasma in the presence of physiologically relevant amounts of hypochlorite. The chaperone activity of hypochlorite-modified α2M involves the formation of stable soluble complexes with misfolded client proteins, including heat-denatured enzymes, oxidized fibrinogen, oxidized LDL, and native or oxidized amyloid β-peptide (Aβ1-42). Here, we show that hypochlorite-modified α2M delivers its misfolded cargo to lipoprotein receptors on macrophages and reduces Aβ1-42 neurotoxicity. Our results support the conclusion that α2M is a specialized chaperone that prevents the extracellular accumulation of misfolded and potentially pathogenic proteins, particularly during innate immune system activity.

  6. Structural Modifications of Continuous Aerogel Films for Low-power, High Performance Sensing Capabilities

    Data.gov (United States)

    National Aeronautics and Space Administration — Recent work has found that TiO2 nanorods and nanowires can be grown from a high-surface area, highly porous TiO2 ambiently-dried aerogel structure through varying...

  7. Long-Term Structural Modification of Water under Microwave Irradiation: Low-Frequency Raman Spectroscopic Measurements

    Directory of Open Access Journals (Sweden)

    A. V. Yakunov

    2017-01-01

    Full Text Available Raman scattering has been used to study the influence of 2.45 GHz microwave on the structure of water. It has been shown that treatment of the distilled water samples by electromagnetic field leads to long-term changes in the vibrational density of states. It was established that the retention time of structural changes of the water samples depends on the sample volume. The experimental results have been interpreted on the basis of the percolation model. It has been suggested that the change in the chemical composition of the water treated by microwaves can lead to a change in the structure of the percolation cluster formed by the network of hydrogen bonds. The time of the equilibrium structure recovery of the percolation cluster after termination of the microwaves depends on the cluster size and is much slower than the recovery in the chemical composition of water.

  8. Peroxynitrous acid induces structural and functional modifications to basement membranes and its key component, laminin

    DEFF Research Database (Denmark)

    Degendorfer, Georg; Chuang, Christine Y.; Hammer, Astrid

    2015-01-01

    Basement membranes (BM) are specialized extracellular matrices underlying endothelial cells in the artery wall. Laminin, the most abundant BM glycoprotein, is a structural and biologically active component. Peroxynitrous acid (ONOOH), a potent oxidizing and nitrating agent, is formed in vivo...

  9. Molecular analysis of carbon ion-induced mutations in Arabidopsis thaliana

    International Nuclear Information System (INIS)

    Shikazono, Naoya; Tanaka, Atsushi; Watanabe, Hiroshi; Tano, Shigemitsu; Yokota, Yukihiko

    1998-01-01

    In order to elucidate the characteristics of the mutations induced by ion particles at the molecular level in plants, mutated loci in carbon ion-induced mutants of Arabidopsis were investigated by PCR and Southern blot analyses. In the present study, two lines of gl1 mutant and two lines of tt4 mutant were isolated after carbon ion-irradiation. Out of four mutants, one had a deletion, other two contained rearrangements, and one had a point-like mutation. From the present result, it was suggested that ion particles induced different kinds of alterations of the DNA and therefore they could produce various types of mutant alleles in plants. (author)

  10. EPR study of N+-ion-induced free radical formation in antibiotic-producers

    International Nuclear Information System (INIS)

    Xie Liqing; Zhang Yinfen; Chen Ruyi; Gao Juncheng; Zhang Peiling; Ying Hengfeng.

    1995-01-01

    Under the room temperature, electron paramagnetic resonance (EPR) spectrometer was used to study free radical formation in antibiotic-producers in order to investigate antibiotic-producer mutagenic breeding, which were induced by N + ion implanting into antibiotic-producers (e.g., Streptomyces ribosidificus, Streptomyces kanamyceticus and the phage-resistant culture of Streptomyces kanamyceticus). The results show that a lot of free radicals can be induced by N + ion implanting into antibiotic-producers, and the yields of the free radicals increase with implanting dose. The death rate of antibiotic-producers rises due to the increase of N + -ion-induced free radical yields. (author)

  11. Energy dependence of ion-induced sputtering yields from monoatomic solids at normal incidence

    International Nuclear Information System (INIS)

    Yamamura, Yasunori; Tawara, Hiro.

    1995-03-01

    The yields of the ion-induced sputtering from monoatomic solids at normal incidence for various ion-target combinations are presented graphically as a function of the incident ion energy. In order to fill the lack of the experimental data, the sputtering yields are also calculated by the Monte Carlo simulation code ACAT for some ion-target combinations. Each graph shows available experimental data points and the ACAT data, together with the sputtering yields calculated by the present empirical formula, whose parameters are determined by the best-fit to available data. (author)

  12. Symposium on fast atom and ion induced mass spectrometry of nonvolatile organic solids

    International Nuclear Information System (INIS)

    McNeal, C.J.

    1982-01-01

    The mechanisms of molecular and fragment ion production and the various parameters affecting ion yields were discussed by 6 invited speakers from Europe, Canada, and the US at this symposium. The work reported was almost equally divided between that using low-energy (keV) primary ion (or atom) beams, e.g. fast atom bombardment mass spectrometry (FABMS) and secondary ion mass spectrometry (SIMS) and that using high energy (MeV) particles, e.g. heavy ion induced mass spectrometry (HIIDMS) and 252 Cf-plasma desorption mass spectrometry ( 252 Cf-PDMS). Both theoretical foundations and observed experimental results for both techniques are included

  13. Pore structure modification of diatomite as sulfuric acid catalyst support by high energy electron beam irradiation and hydrothermal treatment

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chong [Research Center of the Ministry of Education for High Gravity Engineering and Technology, Beijing University of Chemical Technology, Beijing 100029 (China); Zhang, Guilong; Wang, Min [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China); Chen, Jianfeng [Research Center of the Ministry of Education for High Gravity Engineering and Technology, Beijing University of Chemical Technology, Beijing 100029 (China); Cai, Dongqing, E-mail: dqcai@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China); Wu, Zhengyan, E-mail: zywu@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China)

    2014-08-15

    Highlights: • High energy electron beam (HEEB) irradiation and hydrothermal treatment were used. • HEEB irradiation could make the impurities in the pores of diatomite loose. • Hydrothermal treatment (HT) could remove these impurities from the pores. • They could effectively improve pore size distribution and decrease the bulk density. • Catalytic performance of the corresponding catalyst was significantly improved. - Abstract: High energy electron beam (HEEB) irradiation and hydrothermal treatment (HT), were applied in order to remove the impurities and enlarge the pore size of diatomite, making diatomite more suitable to be a catalyst support. The results demonstrated that, through thermal, charge, impact and etching effects, HEEB irradiation could make the impurities in the pores of diatomite loose and remove some of them. Then HT could remove rest of them from the pores and contribute significantly to the modification of the pore size distribution of diatomite due to thermal expansion, water swelling and thermolysis effects. Moreover, the pore structure modification improved the properties (BET (Brunauer–Emmett–Teller) specific surface area, bulk density and pore volume) of diatomite and the catalytic efficiency of the catalyst prepared from the treated diatomite.

  14. Thermo-elasto-plastic simulations of femtosecond laser-induced structural modifications: Application to cavity formation in fused silica

    Science.gov (United States)

    Beuton, Romain; Chimier, Benoît; Breil, Jérôme; Hébert, David; Maire, Pierre-Henri; Duchateau, Guillaume

    2017-11-01

    The absorbed laser energy of a femtosecond laser pulse in a transparent material induces a warm dense matter region relaxation of which may lead to structural modifications in the surrounding cold matter. The modeling of the thermo-elasto-plastic material response is addressed to predict such modifications. It has been developed in a 2D plane geometry and implemented in a hydrodynamic Lagrangian code. The particular case of a tightly focused laser beam in the bulk of fused silica is considered as a first application of the proposed general model. It is shown that the warm dense matter relaxation, influenced by the elasto-plastic behavior of the surrounding cold matter, generates both strong shock and rarefaction waves. Permanent deformations appear in the surrounding solid matter if the induced stress becomes larger than the yield strength. This interaction results in the formation of a sub-micrometric cavity surrounded by an overdense area. This approach also allows one to predict regions where cracks may form. The present modeling can be used to design nanostructures induced by short laser pulses.

  15. Effect of ion irradiation on the surface, structural and mechanical properties of brass

    Science.gov (United States)

    Ahmad, Shahbaz; Bashir, Shazia; Ali, Nisar; Umm-i-Kalsoom; Yousaf, Daniel; Faizan-ul-Haq; Naeem, Athar; Ahmad, Riaz; Khlaeeq-ur-Rahman, M.

    2014-04-01

    Modifications to the surface, structural and mechanical properties of brass after ion irradiation have been investigated. Brass targets were bombarded by carbon ions of 2 MeV energy from a Pelletron linear accelerator for various fluences ranging from 56 × 1012 to 26 × 1013 ions/cm2. A scanning electron microscope and X-ray diffractometer were utilized to analyze the surface morphology and crystallographic structure respectively. To explore the mechanical properties e.g., yield stress, ultimate tensile strength and microhardness of irradiated brass, an universal tensile testing machine and Vickers microhardness tester were used. Scanning electron microscopy results revealed an irregular and randomly distributed sputter morphology for a lower ion fluence. With increasing ion fluence, the incoherently shaped structures were transformed into dendritic structures. Nano/micro sized craters and voids, along with the appearance of pits, were observed at the maximum ion fluence. From X-ray diffraction results, no new phases were observed to be formed in the brass upon irradiation. However, a change in the peak intensity and higher and lower angle shifting were observed, which represents the generation of ion-induced defects and stresses. Analyses confirmed modifications in the mechanical properties of irradiated brass. The yield stress, ultimate tensile strength and hardness initially decreased and then increased with increasing ion fluence. The changes in the mechanical properties of irradiated brass are well correlated with surface and crystallographic modifications and are attributed to the generation, augmentation, recombination and annihilation of the ion-induced defects.

  16. Structural modification of silicon during the formation process of porous silicon

    International Nuclear Information System (INIS)

    Martin-Palma, R.J.; Pascual, L.; Landa-Canovas, A.R.; Herrero, P.; Martinez-Duart, J.M.

    2005-01-01

    Direct examination of porous silicon (PS) by the use of high resolution transmission electron microscopy (HRTEM) allowed us to perform a deep insight into the formation mechanisms of this material. In particular, the structure of the PS/Si interface and that of the silicon nanocrystals that compose porous silicon were analyzed in detail. Furthermore, image processing was used to study in detail the structure of PS. The mechanism of PS formation and lattice matching between the PS layer and the Si substrate is analyzed and discussed. Finally, a formation mechanism for PS based on the experimental observations is proposed

  17. Synthesis and crystal structure of the γ-modifications of US2 and USe2

    International Nuclear Information System (INIS)

    Kohlmann, H.; Beck, H.P.

    1997-01-01

    We report on γ-US 2 and γ-USe 2 which may be synthesized by a presumably topotactic reaction from the corresponding U 3 X 5 compounds and elementary chalcogen. γ-USe 2 can also be prepared by a high pressure transformation of α-USe 2 at 4 GPa and 773 K. The structure of the γ phases could be determined and refined by a Rietveld procedure from powder date. They crystallize in an anti-Fe 2 P-type arrangement. Unusual features of these structures and a possible reaction mechanism for the formation of the compounds are discussed. (orig.)

  18. Structure determination and compositional modification of body-centered tetragonal PX-phase lead titanate

    Czech Academy of Sciences Publication Activity Database

    Wang, J.; Schenk, K.; Carvalho, A.; Wylie-van Eerd, B.; Trodahl, J.; Sandu, C.S.; Bonin, M.; Gregora, Ivan; He, Z.; Yamada, T.; Funakubo, H.; Briddon, P.R.; Setter, N.

    2011-01-01

    Roč. 23, č. 10 (2011), s. 2529-2535 ISSN 0897-4756 R&D Projects: GA AV ČR KAN301370701 Institutional research plan: CEZ:AV0Z10100520 Keywords : lead titanate * fibrous PX phase * structure determination * open channels * Raman scattering Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 7.286, year: 2011

  19. Hydrophobic modification of chitin whisker and its potential application in structuring oil

    NARCIS (Netherlands)

    Huang, Yao; He, Meng; Lu, Ang; Zhou, Weizheng; Stoyanov, S.D.; Pelan, E.G.; Zhang, Lina

    2015-01-01

    A facile approach was developed to modify chitin whiskers by reacting them with bromohexadecane, and the potential application of modified whiskers in structuring oil was evaluated. The results of Fourier transform infrared spectra (FT-IR), wide-angle X-ray diffraction (XRD), elemental analysis,

  20. [The role of DNA methylation and histone modifications in structural maintainance of heterochromatin domains (chromocenters)].

    Science.gov (United States)

    Golyshev, S A; Vikhreva, P N; Sheval', E V; Kir'ianov, G I; Poliakov, V Iu

    2008-01-01

    The effects of DNA methylation inhibitor 5-azacytidine (5-aza-C) and histone acetylation inhibitor trichostatine A (TSA) on the structure of pericentric heterochromatin in cultured mouse cells (L929) has been studied. After 48 h of 5-aza-C treatment, about 85% of the cells demonstrate transformation of chromocenters from ovoid to elongated structures. Hypotonic treatment of these cells reveals tandemly arranged DAPI-positive globules, well distinguishable by light microscopy. The same globular units can be revealed in hypotonic-treated control cells. 48 h of TSA treatment causes dramatic decrease in HP 1alpha content in the cells. Chromocenters in 25% of treated cells became highly decondenced and can not be reliably detected by light and electron microscopy. 85% of cells demonstrate globular chromocenters with low HP 1alpha content. Hypotonic treatment causes transformation of compact chromocenters into ring-like structures, which can be either single or clustered. Rings are formed by uniform fiber, in which no globular subunits are detected. The data obtained are discussed concerning several mechanisms of heterochromatin structure maintenance and the roles of epigenetic marks in them.

  1. Modification of zirconium and hafnium alkoxides : the effect of molecular structure on derived materials

    NARCIS (Netherlands)

    Spijksma, G.I.

    2006-01-01

    This thesis deals with the influence of modifying ligands on the structure and stability of zirconium and hafnium precursors. The applicability of the obtained modified alkoxides has been evaluated for MOCVD and sol-gel. Furthermore, the influence of the introduction of heteroligands on the sol-gel

  2. Fine tuning of the rotary motion by structural modification in light-driven unidirectional molecular motors

    NARCIS (Netherlands)

    Vicario, J; Walko, M; Meetsma, A; Feringa, Ben L.

    2006-01-01

    The introduction of bulky substituents at the stereogenic center of light-driven second-generation molecular motors results in an acceleration of the speed of rotation. This is due to a more strained structure with elongated C=C bonds and a higher energy level of the ground state relative to the

  3. Effects of structural modifications on some physical characteristics of exopolysaccharides from Lactococcus lactis

    NARCIS (Netherlands)

    Tuinier, R.; Casteren, van W.H.M.; Looijesteijn, P.J.; Schols, H.A.; Voragen, A.G.J.; Zoon, P.

    2001-01-01

    The relationship between the primary structure and the chain stiffness of exopolysaccharides (EPSs) and modified EPSs produced by two strains of Lactococcus lactis subsp. cremoris was investigated. The molar mass and radius of gyration of these exopolysaccharides were analyzed by multiangle static

  4. Modification of nonlinear mapping technique for quantitative structure-retention relationship studies

    Czech Academy of Sciences Publication Activity Database

    Cserháti, T.; Forgács, E.; Deyl, Zdeněk; Mikšík, Ivan; Eckhardt, Adam

    2002-01-01

    Roč. 75, č. 1 (2002), s. 13-24 ISSN 0011-1643 Institutional research plan: CEZ:AV0Z5011922 Keywords : Structure-retention relationship * principal component analysis Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 0.722, year: 2002

  5. Enhanced organic photovoltaic properties via structural modifications in PEDOT:PSS due to graphene oxide doping

    Energy Technology Data Exchange (ETDEWEB)

    Goutham, Raj P.; Sandhya, Rani V.; Kanwat, Anil; Jang, Jin, E-mail: jjang@khu.ac.kr

    2016-02-15

    Highlights: • Graphene oxide(GO) blended with PEDOT:PSS is used as HTL for PTB7:PCBM BHJ solar cells. • Increase in conductivity due to structural alterations in PEDOT:PSS by GO addition. • The structural alterations are reaveled under Raman spectroscopy, XPS and AFM. • PEDOT:PSS changed to extended coil due to addition of GO to PEDOT:PSS. • Enhanced conductivity after GO addition to PEDOT:PSS resulted in enhanced PCE. - Abstract: Poly(3,4-thylenedioxythiophene):poly(styrene sulfonate), PEDOT:PSS is a well-known conductive polymer for hole transport in organic devices, the properties of which can be enhanced by doping. Common dopants are metal oxides and nanoparticles. In this study, addition of graphene oxide (GO) to PEDOT:PSS as a dopant is addressed in organic photovoltaics (OPVs). With GO doping, electrical conductivity and transport properties of PEDOT:PSS increases due to structural alterations in the presence of −COOH and −OH functional groups in GO. These structural alterations have been revealed under detailed study of Raman spectra, X-ray photoelectron spectroscopy (XPS) analysis, Topographical and conductive Atom force microscopy (AFM/C-AFM) mapping. OPVs fabricated using PEDOT:PSS: GO (5:1) as a hole transport layer (HTL) exhibited a power conversion efficiency (PCE) of 7.68%, which was higher than the 7.01% that was obtained for the OPVs using pristine PEDOT:PSS.

  6. The fabrication and high temperature stability of biaxially textured Ni tape by ion beam structure modification method

    International Nuclear Information System (INIS)

    Wu, K.; Wang, S.S.; Meng, J.; Han, Z.

    2004-01-01

    For the conventional rolling assisted biaxially textured metallic substrate (RABiTS) process, a large degree of cold rolling deformation and a subsequent high temperature annealing procedure are required to obtain adequately biaxially textured Ni tape. Recently, we have reported a newly developed process, named as ion beam structure modification (ISM), for fabricating biaxially textured Ni tape by use of low energy argon ion beam bombardment. In this paper, the biaxial texture of ISM processed Ni tape and its thermal stability at high temperatures are investigated. Results show that Ni tape processed under optimum ISM conditions, the (2 0 0) rocking curve FWHM is less than 5.7 deg. , and the (1 1 1) phi-scan FWHM is less than 7.5 deg. . High temperature annealing does not impair the biaxial-texture already developed in ISM processed Ni foils, although ISMs should not be regarded as a complete equilibrium process

  7. Effects of an eight-week supervised, structured lifestyle modification programme on anthropometric, metabolic and cardiovascular risk factors in severely obese adults.

    LENUS (Irish Health Repository)

    Crowe, Catherine

    2015-08-01

    Lifestyle modification is fundamental to obesity treatment, but few studies have described the effects of structured lifestyle programmes specifically in bariatric patients. We sought to describe changes in anthropometric and metabolic characteristics in a cohort of bariatric patients after participation in a nurse-led, structured lifestyle programme.

  8. Acanthaster planci outbreak: decline in coral health, coral size structure modification and consequences for obligate decapod assemblages.

    Directory of Open Access Journals (Sweden)

    Matthieu Leray

    Full Text Available Although benthic motile invertebrate communities encompass the vast majority of coral reef diversity, their response to habitat modification has been poorly studied. A variety of benthic species, particularly decapods, provide benefits to their coral host enabling them to cope with environmental stressors, and as a result benefit the overall diversity of coral-associated species. However, little is known about how invertebrate assemblages associated with corals will be affected by global perturbations, (either directly or indirectly via their coral host or their consequences for ecosystem resilience. Analysis of a ten year dataset reveals that the greatest perturbation at Moorea over this time was an outbreak of the corallivorous sea star Acanthaster planci from 2006 to 2009 impacting habitat health, availability and size structure of Pocillopora spp. populations and highlights a positive relationship between coral head size and survival. We then present the results of a mensurative study in 2009 conducted at the end of the perturbation (A. planci outbreak describing how coral-decapod communities change with percent coral mortality for a selected coral species, Pocillopora eydouxi. The loss of coral tissue as a consequence of A. planci consumption led to an increase in rarefied total species diversity, but caused drastic modifications in community composition driven by a shift from coral obligate to non-obligate decapod species. Our study highlights that larger corals left with live tissue in 2009, formed a restricted habitat where coral obligate decapods, including mutualists, could subsist. We conclude that the size structure of Pocillopora populations at the time of an A. planci outbreak may greatly condition the magnitude of coral mortality as well as the persistence of local populations of obligate decapods.

  9. Modification of spontaneous emission from nanodiamond colour centres on a structured surface

    International Nuclear Information System (INIS)

    Inam, F A; Gaebel, T; Bradac, C; Withford, M J; Rabeau, J R; Steel, M J; Stewart, L; Dawes, J M

    2011-01-01

    Colour centres in diamond are promising candidates as a platform for quantum technologies and biomedical imaging based on spins and/or photons. Controlling the emission properties of colour centres in diamond is a key requirement for the development of efficient single-photon sources having high collection efficiency. A number of groups have achieved an enhancement in the emission rate over narrow wavelength ranges by coupling single emitters in nanodiamond crystals to resonant electromagnetic structures. In this paper, we characterize in detail the spontaneous emission rates of nitrogen-vacancy centres at various locations on a structured substrate. We found a factor of 1.5 average enhancement of the total emission rate when nanodiamonds are on an opal photonic crystal surface, and observed changes in the lifetime distribution. We present a model for explaining these observations and associate the lifetime properties with dipole orientation and polarization effects.

  10. Modification of spontaneous emission from nanodiamond colour centres on a structured surface

    Energy Technology Data Exchange (ETDEWEB)

    Inam, F A; Gaebel, T; Bradac, C; Withford, M J; Rabeau, J R; Steel, M J [Centre for Quantum Science and Technology, Department of Physics and Astronomy, Macquarie University, Sydney, NSW 2109 (Australia); Stewart, L; Dawes, J M, E-mail: james.rabeau@mq.edu.au, E-mail: michael.steel@mq.edu.au [MQ Photonics Research Centre, Department of Physics and Astronomy, Macquarie University, Sydney, NSW 2109 (Australia)

    2011-07-15

    Colour centres in diamond are promising candidates as a platform for quantum technologies and biomedical imaging based on spins and/or photons. Controlling the emission properties of colour centres in diamond is a key requirement for the development of efficient single-photon sources having high collection efficiency. A number of groups have achieved an enhancement in the emission rate over narrow wavelength ranges by coupling single emitters in nanodiamond crystals to resonant electromagnetic structures. In this paper, we characterize in detail the spontaneous emission rates of nitrogen-vacancy centres at various locations on a structured substrate. We found a factor of 1.5 average enhancement of the total emission rate when nanodiamonds are on an opal photonic crystal surface, and observed changes in the lifetime distribution. We present a model for explaining these observations and associate the lifetime properties with dipole orientation and polarization effects.

  11. Crystal structures of B-DNA dodecamer containing the epigenetic modifications 5-hydroxymethylcytosine or 5-methylcytosine

    Czech Academy of Sciences Publication Activity Database

    Renčiuk, Daniel; Blacque, O.; Vorlíčková, Michaela; Spingler, B.

    2013-01-01

    Roč. 41, č. 21 (2013), s. 9891-9900 ISSN 0305-1048 R&D Projects: GA ČR GAP205/12/0466; GA MŠk(CZ) ED1.1.00/02.0068 Institutional research plan: CEZ:AV0Z50040702 Institutional support: RVO:68081707 Keywords : NUCLEIC-ACID STRUCTURES * CIRCULAR-DICHROISM * DEOXYRIBONUCLEIC-ACID Subject RIV: BO - Biophysics Impact factor: 8.808, year: 2013

  12. Gestational stress induces persistent depressive-like behavior and structural modifications within the postpartum nucleus accumbens

    Science.gov (United States)

    Haim, Achikam; Sherer, Morgan; Leuner, Benedetta

    2015-01-01

    Postpartum depression (PPD) is a common complication following childbirth experienced by one in every five new mothers. Pregnancy stress enhances vulnerability to PPD and has also been shown to increase depressive-like behavior in postpartum rats. Thus, gestational stress may be an important translational risk factor that can be used to investigate the neurobiological mechanisms underlying PPD. Here we examined the effects of gestational stress on depressive-like behavior during the early/mid and late postpartum periods and evaluated whether this was accompanied by altered structural plasticity in the nucleus accumbens (NAc), a brain region that has been linked to PPD. We show that early/mid (PD8) postpartum female rats exhibited more depressive-like behavior in the forced swim test as compared to late postpartum females (PD22). However, two weeks of restraint stress during pregnancy increased depressive-like behavior regardless of postpartum timepoint. In addition, dendritic length, branching, and spine density on medium spiny neurons in the NAc shell were diminished in postpartum rats that experienced gestational stress although stress-induced reductions in spine density were evident only in early/mid postpartum females. In the NAc core, structural plasticity was not affected by gestational stress but late postpartum females exhibited lower spine density and reduced dendritic length. Overall, these data not only demonstrate structural changes in the NAc across the postpartum period, they also show that postpartum depressive-like behavior following exposure to gestational stress is associated with compromised structural plasticity in the NAc and thus may provide insight into the neural changes that could contribute to PPD. PMID:25359225

  13. Structural Modification of Cobalt Catalysts: Effect of Wetting Studied by X-Ray and Infrared Techniques

    Directory of Open Access Journals (Sweden)

    Khodakov A.

    1999-07-01

    Full Text Available The effect of wetting on the structure and localisation of cobalt species on various supports (Al2O3, SiO2, TiO2, HZSM-5 zeolite was studied using X-ray diffraction, Fourier transform infrared spectroscopy with CO as a molecular probe, X-ray photoelectron spectroscopy and extended X-ray absorption fine structure analysis. Aqueous impregnation to incipient wetness of reduced and passivated cobalt catalysts results, even in the absence of any promoter, in a considerable decrease in the concentration of Co crystalline phases and modifies the surface sites. The decrease in the concentration of Co3O4 crystallites was especially pronounced on silica supported catalysts prepared via impregnation of cobalt and on a mixture of Co3O4 and HZSM-5 zeolite. Saturation with water of the passivated Co/SiO2 sample results in an amorphous solid with a local structure close to that of Co2SiO4. For Co/Al2O3 and Co/TiO2 catalysts, the effect of wetting on the concentration of Co3O4 crystalline phase was considerably smaller.

  14. Magnetic Doppler imaging considering atmospheric structure modifications due to local abundances: a luxury or a necessity?

    Science.gov (United States)

    Kochukhov, O.; Wade, G. A.; Shulyak, D.

    2012-04-01

    Magnetic Doppler imaging is currently the most powerful method of interpreting high-resolution spectropolarimetric observations of stars. This technique has provided the very first maps of stellar magnetic field topologies reconstructed from time series of full Stokes vector spectra, revealing the presence of small-scale magnetic fields on the surfaces of Ap stars. These studies were recently criticised by Stift et al., who claimed that magnetic inversions are not robust and are seriously undermined by neglecting a feedback on the Stokes line profiles from the local atmospheric structure in the regions of enhanced metal abundance. We show that Stift et al. misinterpreted published magnetic Doppler imaging results and consistently neglected some of the most fundamental principles behind magnetic mapping. Using state-of-the-art opacity sampling model atmosphere and polarized radiative transfer codes, we demonstrate that the variation of atmospheric structure across the surface of a star with chemical spots affects the local continuum intensity but is negligible for the normalized local Stokes profiles except for the rare situation of a very strong line in an extremely Fe-rich atmosphere. For the disc-integrated spectra of an Ap star with extreme abundance variations, we find that the assumption of a mean model atmosphere leads to moderate errors in Stokes I but is negligible for the circular and linear polarization spectra. Employing a new magnetic inversion code, which incorporates the horizontal variation of atmospheric structure induced by chemical spots, we reconstructed new maps of magnetic field and Fe abundance for the bright Ap star α2 CVn. The resulting distribution of chemical spots changes insignificantly compared to the previous modelling based on a single model atmosphere, while the magnetic field geometry does not change at all. This shows that the assertions by Stift et al. are exaggerated as a consequence of unreasonable assumptions and

  15. Mass spectrometric comparison of swift heavy ion-induced and anaerobic thermal degradation of polymers

    Science.gov (United States)

    Lima, V.; Hossain, U. H.; Walbert, T.; Seidl, T.; Ensinger, W.

    2018-03-01

    The study of polymers irradiated by highly energetic ions and the resulting radiation-induced degradation is of major importance for space and particle accelerator applications. The mechanism of ion-induced molecular fragmentation of polyethylene, polyethyleneimine and polyamide was investigated by means of mass spectrometry and infrared spectroscopy. The results show that the introduction of nitrogen and oxygen into the polymer influences the stability rendering aliphatic polymers with heteroatoms less stable. A comparison to thermal decomposition data from literature reveals that ion-induced degradation is different in its bond fracture mechanism. While thermal degradation starts at the weakest bond, which is usually the carbon-heteroatom bond, energetic ion irradiation leads in the first step to scission of all types of bonds creating smaller molecular fragments. This is due to the localized extreme energy input under non-equilibrium conditions when the ions transfer kinetic energy onto electrons. These findings are of relevance for the choice of polymers for long-term application in both space and accelerator facilities.

  16. Composite alginate hydrogel microparticulate delivery system of zidovudine hydrochloride based on counter ion induced aggregation.

    Science.gov (United States)

    Roy, Harekrishna; Rao, P Venkateswar; Panda, Sanjay Kumar; Biswal, Asim Kumar; Parida, Kirti Ranjan; Dash, Jharana

    2014-09-01

    The present study deals with preparation of zidovudine loaded microparticle by counter ion induced aggregation method. During this study effect of polyacrylates and hypromellose polymers on release study were investigated. The ion induced aggregated alginate based microparticles were characterized for surface morphology, particle size analysis, drug entrapment study, in-vitro study, Fourier-transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC) study. The result showed Eudragit RL-100 (ERL) based formulations had smoother surface as well as their mean particle sizes were found greater compared with Eudragit RS-100 (ERS) microparticles. Furthermore, drug entrapments were found to be more in ERL formulae as compared with ERS. RL3 released 101.05% drug over a period of 8(th) h and followed Higuchi profile and Fickian diffusion. Moreover, data obtained illustrated that, higher amount of quaternary ammonium group, alkali value, and glass transition temperature may be possible reason for improving permeability of ERL based formulations. It was also noticed, hyroxypropyl methylcellulose (HPMC) K4M premium grade polymer sustained drug release more than HPMC K15M. In addition, drug-excipient interaction study was carried out by FTIR and DSC study.

  17. Inorganic–organic hybrid materials through post-synthesis modification: Impact of the treatment with azides on the mesopore structure

    Directory of Open Access Journals (Sweden)

    Miriam Keppeler

    2011-08-01

    Full Text Available Hybrid, hierarchically organized, monolithic silica gels, comprising periodically arranged mesopores and a cellular macroscopic network, have been prepared through a co-condensation reaction of tetrakis(2-hydroxyethylorthosilicate with chloromethyl-trimethoxysilane or 3-(chloropropyl-triethoxysilane. Subsequent conversion of the chloro groups into azido groups, by nucleophilic substitution with NaN3 in N,N-dimethylformamide, was conducted upon preservation of the monolithic structure. However, treatment with NaN3 had a strong influence on the structure in the mesoporous regime, with changes such as an increase of mesopore diameter, pore volume and lattice constants, as well as a concomitant decrease of the pore wall thickness, as confirmed by small angle X-ray scattering, transmission electron microscopy, and nitrogen sorption analysis. Similar effects were observed for unmodified silica gels by simple ageing in azide-containing media, whether a relatively small or a sterically demanding counter ion (Na+ or (H3C4N+ was used. The structural modification did not seem to depend greatly on whether an organic aprotic solvent (N,N-dimethylformamide, 1,1,3,3-tetramethylurea, 1,3-dimethyl-2-imidazolidinone or a protic solvent that can form hydrogen bonds, such as water, was used.

  18. Structural Modifications of Fructans in Aloe barbadensis Miller (Aloe Vera) Grown under Water Stress.

    Science.gov (United States)

    Salinas, Carlos; Handford, Michael; Pauly, Markus; Dupree, Paul; Cardemil, Liliana

    2016-01-01

    Aloe barbadensis Miller (Aloe vera) has a Crassulaceae acid metabolism which grants the plant great tolerance to water restrictions. Carbohydrates such as acemannans and fructans are among the molecules responsible for tolerating water deficit in other plant species. Nevertheless, fructans, which are prebiotic compounds, have not been described nor studied in Aloe vera, whose leaf gel is known to possess beneficial pharmaceutical, nutritional and cosmetic properties. As Aloe vera is frequently cultivated in semi-arid conditions, like those found in northern Chile, we investigated the effect of water deficit on fructan composition and structure. For this, plants were subjected to different irrigation regimes of 100%, 75%, 50% and 25% field capacity (FC). There was a significant increase in the total sugars, soluble sugars and oligo and polyfructans in plants subjected to water deficit, compared to the control condition (100% FC) in both leaf tips and bases. The amounts of fructans were also greater in the bases compared to the leaf tips in all water treatments. Fructans also increase in degree of polymerization with increasing water deficit. Glycosidic linkage analyses by GC-MS, led to the conclusion that there are structural differences between the fructans present in the leaves of control plants with respect to plants irrigated with 50% and 25% FC. Therefore, in non-stressed plants, the inulin, neo-inulin and neo-levan type of fructans predominate, while in the most stressful conditions for the plant, Aloe vera also synthesizes fructans with a more branched structure, the neofructans. To our knowledge, the synthesis and the protective role of neo-fructans under extreme water deficit has not been previously reported.

  19. Structure-Based Modification of a Clostridium difficile-Targeting Endolysin Affects Activity and Host Range▿

    Science.gov (United States)

    Mayer, Melinda J.; Garefalaki, Vasiliki; Spoerl, Rebecca; Narbad, Arjan; Meijers, Rob

    2011-01-01

    Endolysin CD27L causes cell lysis of the pathogen Clostridium difficile, a major cause of nosocomial infection. We report a structural and functional analysis of the catalytic activity of CD27L against C. difficile and other bacterial strains. We show that truncation of the endolysin to the N-terminal domain, CD27L1–179, gave an increased lytic activity against cells of C. difficile, while the C-terminal region, CD27L180–270, failed to produce lysis. CD27L1–179 also has increased activity against other bacterial species that are targeted by the full-length protein and in addition was able to lyse some CD27L-insensitive strains. However, CD27L1–179 retained a measure of specificity, failing to lyse a wide range of bacteria. The use of green fluorescent protein (GFP)-labeled proteins demonstrated that both CD27L and CD27L1–179 bound to C. difficile cell walls. The crystal structure of CD27L1–179 confirms that the enzyme is a zinc-dependent N-acetylmuramoyl-l-alanine amidase. A structure-based sequence analysis allowed us to identify four catalytic residues, a proton relay cascade, and a substrate binding pocket. A BLAST search shows that the closest-related amidases almost exclusively target Clostridia. This implied that the catalytic domain alone contained features that target a specific bacterial species. To test this hypothesis, we modified Leu 98 to a Trp residue which is found in an endolysin from a bacteriophage of Listeria monocytogenes (PlyPSA). This mutation in CD27L resulted in an increased activity against selected serotypes of L. monocytogenes, demonstrating the potential to tune the species specificity of the catalytic domain of an endolysin. PMID:21803993

  20. Structure-based modification of a Clostridium difficile-targeting endolysin affects activity and host range.

    Science.gov (United States)

    Mayer, Melinda J; Garefalaki, Vasiliki; Spoerl, Rebecca; Narbad, Arjan; Meijers, Rob

    2011-10-01

    Endolysin CD27L causes cell lysis of the pathogen Clostridium difficile, a major cause of nosocomial infection. We report a structural and functional analysis of the catalytic activity of CD27L against C. difficile and other bacterial strains. We show that truncation of the endolysin to the N-terminal domain, CD27L1-179, gave an increased lytic activity against cells of C. difficile, while the C-terminal region, CD27L180-270, failed to produce lysis. CD27L1-179 also has increased activity against other bacterial species that are targeted by the full-length protein and in addition was able to lyse some CD27L-insensitive strains. However, CD27L1-179 retained a measure of specificity, failing to lyse a wide range of bacteria. The use of green fluorescent protein (GFP)-labeled proteins demonstrated that both CD27L and CD27L1-179 bound to C. difficile cell walls. The crystal structure of CD27L1-179 confirms that the enzyme is a zinc-dependent N-acetylmuramoyl-l-alanine amidase. A structure-based sequence analysis allowed us to identify four catalytic residues, a proton relay cascade, and a substrate binding pocket. A BLAST search shows that the closest-related amidases almost exclusively target Clostridia. This implied that the catalytic domain alone contained features that target a specific bacterial species. To test this hypothesis, we modified Leu 98 to a Trp residue which is found in an endolysin from a bacteriophage of Listeria monocytogenes (PlyPSA). This mutation in CD27L resulted in an increased activity against selected serotypes of L. monocytogenes, demonstrating the potential to tune the species specificity of the catalytic domain of an endolysin.

  1. Structural Modifications of Fructans in Aloe barbadensis Miller (Aloe Vera Grown under Water Stress.

    Directory of Open Access Journals (Sweden)

    Carlos Salinas

    Full Text Available Aloe barbadensis Miller (Aloe vera has a Crassulaceae acid metabolism which grants the plant great tolerance to water restrictions. Carbohydrates such as acemannans and fructans are among the molecules responsible for tolerating water deficit in other plant species. Nevertheless, fructans, which are prebiotic compounds, have not been described nor studied in Aloe vera, whose leaf gel is known to possess beneficial pharmaceutical, nutritional and cosmetic properties. As Aloe vera is frequently cultivated in semi-arid conditions, like those found in northern Chile, we investigated the effect of water deficit on fructan composition and structure. For this, plants were subjected to different irrigation regimes of 100%, 75%, 50% and 25% field capacity (FC. There was a significant increase in the total sugars, soluble sugars and oligo and polyfructans in plants subjected to water deficit, compared to the control condition (100% FC in both leaf tips and bases. The amounts of fructans were also greater in the bases compared to the leaf tips in all water treatments. Fructans also increase in degree of polymerization with increasing water deficit. Glycosidic linkage analyses by GC-MS, led to the conclusion that there are structural differences between the fructans present in the leaves of control plants with respect to plants irrigated with 50% and 25% FC. Therefore, in non-stressed plants, the inulin, neo-inulin and neo-levan type of fructans predominate, while in the most stressful conditions for the plant, Aloe vera also synthesizes fructans with a more branched structure, the neofructans. To our knowledge, the synthesis and the protective role of neo-fructans under extreme water deficit has not been previously reported.

  2. Isoenergic modification of whey protein structure by denaturation and crosslinking using transglutaminase

    DEFF Research Database (Denmark)

    Stender, Emil G. P.; Koutina, Glykeria; Almdal, Kristoffer

    2018-01-01

    Transglutaminase (TG) catalyzes formation of covalent bonds between lysine and glutamine side chains and has applications in manipulation of food structure. Physical properties of a whey protein mixture (SPC) denatured either at elevated pH or by heat-treatment and followed by TG catalyzed......, thus heating caused the largest exposure of the hydrophobic core of SPC proteins, which was decreased by crosslinking. The particle size of the treated SPC samples increased upon crosslinking by TG. Moreover, the particle morphology depended on the type of denaturing treatment, thus heat-treated SPC...

  3. Gamma-stimulated modification of structure and mechanical properties of silicon crystals

    International Nuclear Information System (INIS)

    Khaydarov, T.K.; Khamraeva, R.N.; Rustamova, V.M.; Ibragimova, E.M.; Kalanov, M.U.; Abdurakhimov, A.A.; Abdurakhmanov, A.A.

    2004-01-01

    Full text: The paper presents the results of gamma-irradiation effect on the fine structure and mechanical properties of silicon crystals. The objects of researches were p-Si single crystals with the following characteristics: ρ ≅ 10Ω · cm; N D ≅ 10 2 cm -2 ; N O ≅ 10 17 cm -3 ; N B ≅ 6· 10 15 cm -3 . The plate size were 20.8·4.1· 1.2 mm 3 with the surface oriented along {111}. The structure was studied at the diffractometer DRON-UM1 with CuK α - radiation ( λ = 0.1542 nm). The intrinsic friction (Q -1 ) of the samples was measured with the ultra-sonic resonance technique at the frequency of 148 kHz of the plate bending oscillations. The samples were irradiated at the INP AS RUz 60 Co gamma-facility (E γ ≅ 1.2 MeV) in the dose range of 10 1 † 10 7 Gy at 320 K. The dose dependence of Q -1 had a non-monotonous character. The irradiation to the dose of 5·10 3 Gy resulted in increasing the initial value of Q -1 due to irradiation induced growth of the point defect concentration and accumulating of the elastic lattice strains. It is also evidenced by the symmetric broadening of the structure reflection (111). At the dose of 5 ·10 3 Gy the strain value seems to gain the upper fluidity limit of (6 †15) ·10 -8 N/m 2 , after which a weak splitting of the (111) reflection appears, meaning the beginning of twin formation in the form of insertion stock defects with partial dislocations. At dose increasing to 10 4 Gy the twins cause the sharp drop of Q -1 , related with decreasing of the elastic strains, which stops at the dose of 5·10 4 Gy probably due to reaching the lower limit of fluidity for silicon ((1† 4) · 10 -8 N/m 2 ), when the process of the twin defect formation completes. This mechanism is confirmed by the total splitting of the structure peak (111) and practical independence of Q -1 on dose till 10 7 Gy. Thus, gamma-irradiation in the studied dose range modifies the existing lattice imperfectness, that influences upon both mechanical

  4. Modifications in structure and interaction of nanoparticle-protein-surfactant complexes in electrolyte solution

    Science.gov (United States)

    Mehan, Sumit; Kumar, S.; Aswal, V. K.; Schweins, R.

    2016-05-01

    SANS experiments of three-component system of anionic silica nanoparticles, anionic BSA protein and anionic SDS surfactants have been carried out without and with electrolyte in aqueous solution. In both the cases, the interaction of surfactant with protein results in formation of bead-necklace structure of protein-surfactant complexes in solution. These protein-surfactant complexes interact very differently with nanoparticles in absence and presence of electrolyte. In absence of electrolyte, nanoparticles remain in dispersed phase in solution, whereas with the addition of electrolyte the nanoparticles fractal aggregates are formed. SANS describes the phase behavior to be governed by competition of electrostatic and depletion interactions among the components solution.

  5. Large distance modification of Newtonian potential and structure formation in universe

    Science.gov (United States)

    Hameeda, Mir; Upadhyay, Sudhaker; Faizal, Mir; Ali, Ahmed F.; Pourhassan, Behnam

    2018-03-01

    In this paper, we study the effects of super-light brane world perturbative modes on structure formation in our universe. As these modes modify the large distance behavior of Newtonian potential, they effect the clustering of a system of galaxies. So, we explicitly calculate the clustering of galaxies interacting through such a modified Newtonian potential. We use a suitable approximation for analyzing this system of galaxies, and discuss the validity of such approximations. We observe that such corrections also modify the virial theorem for such a system of galaxies.

  6. [Physiological and structural modifications induced by cadmium-calcium interaction in tomato (Lycopersicon esculentum)].

    Science.gov (United States)

    Boulila Zoghlami, Latifa; Djebali, Wahbi; Chaïbi, Wided; Ghorbel, Mohamed Habib

    2006-09-01

    Tomato seedlings (Lycopersicon esculentum), initially cultivated in a basic nutrient solution during 12 days, were treated with increasing CdCl(2) concentrations for 10 days. The results showed that cadmium inhibited the weight growth depending on the metal concentration and the plant organ. In the presence of 20 microM CdCl(2), the addition of calcium, 0.1 to 10 mM of CaCl(2) in the culture medium, improved especially the biomass production and the mineral composition of the plants in concomitance with an increase in the contents of photosynthetic pigments. Histological study at the hypocotyle level revealed that cadmium (20 microM) induced a restriction of the tissue territories as well as meristem formations differentiating in a root structure. At this concentration, the addition of CaCl(2) (5 microM) was characterized by an opposite effect with absence of meristem structures. The overall results suggest that the alteration of some plant growth process after exposure to cadmium can be attenuated by an adequate calcium contribution in culture medium.

  7. X-ray irradiation-induced structural modifications in PM-355 polymeric nuclear track detector film

    Science.gov (United States)

    Nouh, S. A.; Bahareth, Radiyah A.; Abutalib, M. M.

    2014-06-01

    Samples from sheets of the polymeric material PM-355 have been exposed to X-rays from a 50 kV X-ray tube in the dose range of 10-300 kGy. The resultant effect of X-ray irradiation on the structural properties of PM-355 has been investigated using different techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Vickers hardness and refractive index measurements. The results indicate that the X-ray irradiation of PM-355 in the dose range of 10-20 kGy causes initially chain scission. Above 20 and up to 100 kGy, the active free radicals produced from scission contribute to chemical reactions that lead to the crosslinking. Thus, the X-ray irradiation in the dose range of 20-100 kGy leads to a more compact structure of the PM-355 polymer, resulting in an enhancement of its Vickers hardness and refractive index. Moreover, the irradiation in the dose range of 100-300 kGy leads to the predominance of the degradation. This degradation is reported by FTIR spectroscopy and enhances the degree of ordering in the degraded samples as revealed by XRD technique. Additionally, it decreases both the Vickers hardness and refractive index of the PM-355 samples.

  8. Structural and surface modifications of carbon nanotubes when submitted to high temperature annealing treatments

    Energy Technology Data Exchange (ETDEWEB)

    Castillejos, E. [Instituto de Catalisis y Petroleoquimica, ICP-CSIC, Campus de Cantoblanco, 28046 Madrid (Spain); Bachiller-Baeza, B. [Instituto de Catalisis y Petroleoquimica, ICP-CSIC, Campus de Cantoblanco, 28046 Madrid (Spain); Unidad Asociada UNED/ICP-CSIC Group for Molecular Design of Heterogeneous Catalysts, Madrid (Spain); Perez-Cadenas, M.; Gallegos-Suarez, E. [Dpto. de Quimica Inorganica y Tecnica, UNED, 28040 Madrid (Spain); Rodriguez-Ramos, I. [Instituto de Catalisis y Petroleoquimica, ICP-CSIC, Campus de Cantoblanco, 28046 Madrid (Spain); Unidad Asociada UNED/ICP-CSIC Group for Molecular Design of Heterogeneous Catalysts, Madrid (Spain); Guerrero-Ruiz, A. [Unidad Asociada UNED/ICP-CSIC Group for Molecular Design of Heterogeneous Catalysts, Madrid (Spain); Dpto. de Quimica Inorganica y Tecnica, UNED, 28040 Madrid (Spain); Tamargo-Martinez, K., E-mail: katia@incar.csic.es [Instituto Nacional del Carbon, INCAR-CSIC, Apartado 73, 33080 Oviedo (Spain); Martinez-Alonso, A.; Tascon, J.M.D. [Instituto Nacional del Carbon, INCAR-CSIC, Apartado 73, 33080 Oviedo (Spain)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Multiwall carbon nanotubes (MWCNTs), pristine and heat-treated at 2873 K, were comparatively characterized using HRTEM, SEM, nitrogen adsorption, Raman spectroscopy and immersion calorimetry. Black-Right-Pointing-Pointer Annealing at 2873 K produced removal of amorphous phases, ordering of graphene layers and structural changes inside the cylindrical mesopores. Black-Right-Pointing-Pointer Immersion enthalpies in organic liquids indicated the existence of specific {pi}-{pi} electronic interactions between aromatic molecules and the surface of heat-treated MWCNTs. - Abstract: Multiwall carbon nanotubes (MWCNTs) were synthesized using a chemical vapour deposition procedure using acetylene as source of carbon, iron pentacarbonyl as catalyst and an inert carrier gas. An aliquot of these MWCNTs was heat-treated at 2873 K under inert atmosphere (Ar). The two carbon nanotube samples where characterized using high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy, nitrogen adsorption at 77 K, Raman spectroscopy, and immersion calorimetry in toluene, methanol and methylcyclohexane. HRTEM images confirmed that high-temperature treatment removed amorphous carbon, the graphene layers being better graphitized, and also some structural changes inside the cylindrical mesopores took place. Immersion enthalpies in toluene, in which molecules are present as aromatic functions, indicated the existence of specific {pi}-{pi} electronic interactions between such molecules and the surface of heat-treated MWCNTs.

  9. Non-enzymatic modifications in metallothioneins connected to lipid membrane damages: structural and biomimetic studies under reductive radical stress.

    Science.gov (United States)

    Torreggiani, Armida; Chatgilialoglu, Chryssostomos; Ferreri, Carla; Melchiorre, Michele; Atrian, Silvia; Capdevila, Merce'

    2013-10-30

    . The chemical mechanism involving sulfur-containing moieties under reductive conditions discloses new scenarios that bring to the loss of sulfur-centered radicals by desulfurization reactions that change the natural sequences of MTs. Ala is a genetically coded amino acid, therefore the mutation of Cys to Ala occurring to a sequence by the radical process so far discussed, corresponds to a post-translational modification. Research on such mutation connected also to a free radical stress will be important to contribute for a complete picture of the degeneration associated to diseases and aging. Analogously, the Met to Aba mutation occurring after reductive stress transforms a natural amino acid into a natural, non-genetically-coded congener. Aba corresponds to a homologation of the alkyl chains normally present in genetically codified amino acids, such as methyl (in Ala) and isopropyl (in Leu), with an ethyl unit. Based on alkyl substitution, this modification can therefore be studied in order to understand its general consequences on the structure-activity relationships in proteins and, in particular, on molecular interactions. This article is part of a Special issue entitled: Posttranslational Protein modifications in biology and Medicine. Copyright © 2013 Elsevier B.V. All rights reserved.

  10. Effect of structural modifications on the drying kinetics of foods: changes in volume, surface area and product shape

    Directory of Open Access Journals (Sweden)

    Antonio De Michelis

    2013-10-01

    Full Text Available Macro and micro-structural changes take place during food dehydration. Macro-structural changes encompass modifications in shape, area and volume. Studies of such changes are important because dehydration kinetics (essential for calculating industrial dryers may be highly influenced by changes in food shape and dimensions. The overall changes in volume, surface area (“shrinkage” and shape (Heywood factor, with provides a close description of food shape were determined experimentally, and the results were correlated with simple expressions. Hence, although dehydration kinetics can be modeled with simplified overall shrinkage expressions, the possibility of selecting a suitable geometry and predicting the characteristics dimensions will provide higher accuracy. An additional unresolved problem is the lack of a general model that predicts macro-structural changes for various foods and diverse geometries. In this work, based on experimental data of sweet and sour cherries, and rose hip fruits, a simplified general model to predict changes in volume and surface area are proposed. To estimate how the changes in characteristic dimensions affect the kinetic studies, experimental drying curves for the three fruits by means of a diffusional model considered the following variants for the characteristic dimensions: (i The radius of the fresh food, assumed constant; (ii The radius of the partially dehydrated product; (iii The radius predicted by the correlation for structural changes, especially volume, obtained in this work and generalized for the three fruits, and (iv to demonstrate the need to study the macro-structural changes for all dehydrated foods, also be present the case of a restructured food.

  11. Design and evaluation of meningococcal vaccines through structure-based modification of host and pathogen molecules.

    Directory of Open Access Journals (Sweden)

    Steven Johnson

    Full Text Available Neisseria meningitis remains a leading cause of sepsis and meningitis, and vaccines are required to prevent infections by this important human pathogen. Factor H binding protein (fHbp is a key antigen that elicits protective immunity against the meningococcus and recruits the host complement regulator, fH. As the high affinity interaction between fHbp and fH could impair immune responses, we sought to identify non-functional fHbps that could act as effective immunogens. This was achieved by alanine substitution of fHbps from all three variant groups (V1, V2 and V3 fHbp of the protein; while some residues affected fH binding in each variant group, the distribution of key amino underlying the interaction with fH differed between the V1, V2 and V3 proteins. The atomic structure of V3 fHbp in complex with fH and of the C-terminal barrel of V2 fHbp provide explanations to the differences in the precise nature of their interactions with fH, and the instability of the V2 protein. To develop transgenic models to assess the efficacy of non-functional fHbps, we determined the structural basis of the low level of interaction between fHbp and murine fH; in addition to changes in amino acids in the fHbp binding site, murine fH has a distinct conformation compared with the human protein that would sterically inhibit binding to fHbp. Non-functional V1 fHbps were further characterised by binding and structural studies, and shown in non-transgenic and transgenic mice (expressing chimeric fH that binds fHbp and precisely regulates complement system to retain their immunogenicity. Our findings provide a catalogue of non-functional fHbps from all variant groups that can be included in new generation meningococcal vaccines, and establish proof-in-principle for clinical studies to compare their efficacy with wild-type fHbps.

  12. Design and evaluation of meningococcal vaccines through structure-based modification of host and pathogen molecules.

    Science.gov (United States)

    Johnson, Steven; Tan, Lionel; van der Veen, Stijn; Caesar, Joseph; Goicoechea De Jorge, Elena; Harding, Rachel J; Bai, Xilian; Exley, Rachel M; Ward, Philip N; Ruivo, Nicola; Trivedi, Kaushali; Cumber, Elspeth; Jones, Rhian; Newham, Luke; Staunton, David; Ufret-Vincenty, Rafael; Borrow, Ray; Pickering, Matthew C; Lea, Susan M; Tang, Christoph M

    2012-01-01

    Neisseria meningitis remains a leading cause of sepsis and meningitis, and vaccines are required to prevent infections by this important human pathogen. Factor H binding protein (fHbp) is a key antigen that elicits protective immunity against the meningococcus and recruits the host complement regulator, fH. As the high affinity interaction between fHbp and fH could impair immune responses, we sought to identify non-functional fHbps that could act as effective immunogens. This was achieved by alanine substitution of fHbps from all three variant groups (V1, V2 and V3 fHbp) of the protein; while some residues affected fH binding in each variant group, the distribution of key amino underlying the interaction with fH differed between the V1, V2 and V3 proteins. The atomic structure of V3 fHbp in complex with fH and of the C-terminal barrel of V2 fHbp provide explanations to the differences in the precise nature of their interactions with fH, and the instability of the V2 protein. To develop transgenic models to assess the efficacy of non-functional fHbps, we determined the structural basis of the low level of interaction between fHbp and murine fH; in addition to changes in amino acids in the fHbp binding site, murine fH has a distinct conformation compared with the human protein that would sterically inhibit binding to fHbp. Non-functional V1 fHbps were further characterised by binding and structural studies, and shown in non-transgenic and transgenic mice (expressing chimeric fH that binds fHbp and precisely regulates complement system) to retain their immunogenicity. Our findings provide a catalogue of non-functional fHbps from all variant groups that can be included in new generation meningococcal vaccines, and establish proof-in-principle for clinical studies to compare their efficacy with wild-type fHbps.

  13. Structure-immunosuppressive activity relationships of new analogues of 15-deoxyspergualin. 1. Structural modifications of the hydroxyglycine moiety.

    Science.gov (United States)

    Lebreton, L; Annat, J; Derrepas, P; Dutartre, P; Renaut, P

    1999-01-28

    A series of new analogues of 15-deoxyspergualin (DSG), an immunosuppressive agent currently commercialized in Japan, was synthesized and tested in a graft-versus-host disease (GVHD) model in mice. Using the general concept of bioisosteric replacement, variations of the hydroxyglycine central "C" region were made in order to determine its optimum structure in terms of in vivo immunosuppressive activity. By this way, the malonic derivative 13a was discovered as the first example of a new series of potent immunosuppressive agents encompassing a retro-amide bond linked to the hexyl-guanidino moiety. Structure-activity relationships of this series were studied by synthesizing compounds 13g-i and 13k-s. Variation of the "right-amide" of 13a led to the urea 19a and the carbamates 23 and 27a which proved to be equally active as DSG in our GVHD model. Finally 27a was found to be the most potent derivative, being slightly more active than DSG in a heart allotransplantation model in rats. Due to the absence of chiral center in its structure and to its improved chemical stability compared to DSG, 27a was selected as a candidate for clinical evaluation.

  14. Structural features of silver-doped phosphate glasses in zone of femtosecond laser-induced modification

    International Nuclear Information System (INIS)

    Vasileva, A.A.; Nazarov, I.A.; Olshin, P.K.; Povolotskiy, A.V.; Sokolov, I.A.; Manshina, A.A.

    2015-01-01

    Femtosecond (fs) laser writing of two-dimensional microstructures (waveguides) is demonstrated in bulk phosphate glasses doped with silver ions. Silver-content phosphate and silver-content niobium–phosphate glasses with high concentration of silver oxide 55 mol% were used as samples for fs laser writing. The chemical network structure of the synthesized samples is analyzed through Raman spectroscopy and was found to be strongly sensitive to Nb incorporation. It was found that the direct laser writing process enables not only reorganization of glass network, but also formation of color centers and silver nanoparticles that are revealed in appearance of luminescence signal and plasmon absorption. The process of NPs' formation is more efficient for Nb-phosphate glass, while color centers are preferably formed in phosphate glass. - Graphical abstract: Formation of silver NPs on the surface of 0.5Ag 2 O–0.4P 2 O 5 –0,1Nb 2 O 5 glass induced by CW laser irradiation. - Highlights: • The structure of 0.5Ag 2 O–0.1Nb 2 O 5 –0.4P 2 O 5 and 0.55Ag 2 O–0.45P 2 O 5 glasses was investigated by Raman spectroscopy. • Fs laser writing induces formation of silver NPs in investigated glasses. • Surface plasmon resonance in the absorption spectra confirms the formation of NP. • The possibility of CW laser induced formation of silver NPs on the surface of sample with niobium is shown

  15. Visualization of soil structure and pore structure modifications by pioneering ground beetles (Cicindelidae) in surface sediments of an artificial catchment

    Science.gov (United States)

    Badorreck, Annika; Gerke, Horst H.; Weller, Ulrich; Vontobel, Peter

    2010-05-01

    An artificial catchment was constructed to study initial soil and ecosystem development. As a key process, the pore structure dynamics in the soil at the surface strongly influences erosion, infiltration, matter dynamics, and vegetation establishment. Little is known, however, about the first macropore formation in the very early stage. This presentation focuses on observations of soil pore geometry and its effect on water flow at the surface comparing samples from three sites in the catchment and in an adjacent "younger" site composed of comparable sediments. The surface soil was sampled in cylindrical plastic rings (10 cm³) down to 2 cm depth in three replicates each site and six where caves from pioneering ground-dwelling beetles Cicindelidae were found. The samples were scanned with micro-X-ray computed tomography (at UFZ-Halle, Germany) with a resolution of 0.084 mm. The infiltration dynamics were visualized with neutronradiography (at Paul-Scherer-Institute, Switzerland) on slab-type soil samples in 2D. The micro-tomographies exhibit formation of surface sealing whose thickness and intensity vary with silt and clay content. The CT images show several coarser- and finer-textured micro-layers at the sample surfaces that were formed as a consequence of repeated washing in of finer particles in underlying coarser sediment. In micro-depressions, the uppermost layers consist of sorted fine sand and silt due to wind erosion. Similar as for desert pavements, a vesicular pore structure developed in these sediments on top, but also scattered in fine sand- and silt-enriched micro-layers. The ground-dwelling activity of Cicindelidae beetles greatly modifies the soil structure through forming caves in the first centimetres of the soil. Older collapsed caves, which form isolated pores within mixed zones, were also found. The infiltration rates were severely affected both, by surface crusts and activity of ground-dwelling beetles. The observations demonstrate relatively

  16. Simultaneous Phase Transfer and Surface Modification of TiO₂ Nanoparticles Using Alkylphosphonic Acids: Optimization and Structure of the Organosols.

    Science.gov (United States)

    Schmitt Pauly, Céline; Genix, Anne-Caroline; Alauzun, Johan G; Guerrero, Gilles; Appavou, Marie-Sousai; Pérez, Javier; Oberdisse, Julian; Mutin, P Hubert

    2015-10-13

    An original protocol of simultaneous surface modification and transfer from aqueous to organic phases of anatase TiO2 nanoparticles (NPs) using alkylphosphonic acids (PAs) is studied. The influence of the solvent, the nature and concentration of the PA, and the size, concentration, and aggregation state of the TiO2 NPs was investigated. Complete transfer was observed for linear alkyl chains (5, 8, 12, and 18 C atoms), even at very high sol concentrations. After transfer, the grafted NPs were characterized by (31)P solid-state MAS NMR. The dispersion state of NPs before and after phase transfer was monitored by dynamic light scattering (DLS). Small-angle neutron scattering (SANS) was used to characterize the structure of PA-grafted NPs in the organic solvent. Using a quantitative core-shell model cross-checked under different contrast conditions, it is found that the primary particles making up the NPs are homogeneously grafted with a solvated PA-layer. The nanometric thickness of the latter is shown to increase with the length of the linear carbon chain of the PA, independent of the size of the primary TiO2 NP. Interestingly, a reversible temperature-dependent aggregation was evidenced visually for C18PA, and confirmed by DLS and SANS: heating the sample induces the breakup of aggregates, which reassemble upon cooling. Finally, in the case of NPs agglomerated by playing with the pH or the salt concentration of the sols, the phase transfer with PA is capable of redispersing the agglomerates. This new and highly versatile method of NP surface modification with PAs and simultaneous transfer is thus well suited for obtaining well-dispersed grafted NPs.

  17. Tyrosine Modifications in Aging

    OpenAIRE

    Feeney, Maria B.; Schöneich, Christian

    2012-01-01

    Significance: The understanding of physiological and pathological processes involving protein oxidation, particularly under conditions of aging and oxidative stress, can be aided by proteomic identification of proteins that accumulate oxidative post-translational modifications only if these detected modifications are connected to functional consequences. The modification of tyrosine (Tyr) residues can elicit significant changes in protein structure and function, which, in some cases, may cont...

  18. Influence of organic modification on the structure and properties of polyurethane/sepiolite nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Chen Hongxiang, E-mail: chenhx_916@hotmail.com [Hubei Key Laboratory of Coal Conversion and New Carbon Material, College of Chemical Engineering and Technology, Wuhan University of Science and Technology, 947 Heping Road, 430081 Wuhan, Hubei (China); Zeng Danlin [Hubei Key Laboratory of Coal Conversion and New Carbon Material, College of Chemical Engineering and Technology, Wuhan University of Science and Technology, 947 Heping Road, 430081 Wuhan, Hubei (China); Xiao Xiaoqin [College of Machinery and Automation, Wuhan University of Science and Technology, 430081 Wuhan (China); Zheng Maosheng [Institute of Condensed Physics and Materials, Northwest University, 710069 Xi' an (China); Ke Changmei; Li Yanjun [Hubei Key Laboratory of Coal Conversion and New Carbon Material, College of Chemical Engineering and Technology, Wuhan University of Science and Technology, 947 Heping Road, 430081 Wuhan, Hubei (China)

    2011-01-25

    Research highlights: {yields} KH550 was the best among the three organic modifiers by comparing tensile properties, water resistance and swelling rate. {yields} FTIR revealed the strong interaction between KH550-Sp and the PU matrix. {yields} TEM revealed the compatibility of KH550-Sp and PU was improved. {yields} SEM confirmed the good dispersion of KH550-Sp in PU matrix. - Abstract: The polyurethane (PU) nanocomposites were prepared using organomodified sepiolite (organo-Sp) by in situ polymerization method. The clay was modified with three different organic modifiers such as {gamma}-aminopropyltriethoxylsilane (KH550), hexadecyltrimethylammonium bromide (CTAB) and lauric acid (LA). The morphology and the dispersion of organo-Sp in polyurethane were characterized by scanning electron microscope, transmission electron microscope and Fourier transform infrared spectroscopy. The influence of organo-Sp on the tensile properties, water resistance and swelling rate of polyurethane composites was studied. The results showed the properties and structure of polyurethane nanocomposites were related to the kind of organic modifier.

  19. The structural modification of cassava starch using a saline water pretreatment

    Directory of Open Access Journals (Sweden)

    Hanny Frans SANGIAN

    2018-04-01

    Full Text Available Abstract The cassava has been modified successfully by using the saline water, which was abundantly available on the planet. The biomass was submerged in saline waters that salt concentrations were altered at 0, 3.5 percent (seawater and 10 percent (w/w and were kept 5 days. After recovery by washing steps, the treated solids were characterized by using XRD (X-ray diffraction , FTIR (Fourier transform infra-red, and SEM (Scanning electron microscopic. The results showed that the XRD pattern of saline water pretreatment decreased significantly. The biggest decrease of X-ray intensity occurred at around 18o. Meanwhile, the fingerprint of FTIR revealed the transmittance intensity of infra-red ray of saline water treated solid inclined for all wave constant numbers, suggesting that many hydrogen bonds were disconnected. Those findings also were enhanced by SEM pictures that showed the change of surface morphology of treated biomass. It was indicative that cassava structure was modified becoming more textured after employing saline water pretreatment. This work is an innovative finding to gradually substitute commercial ionic liquids that are very expensive with saline water for biomass pretreatment.

  20. Laser structuring and modification of surfaces for chemical and medical micro components

    Science.gov (United States)

    Bremus-Koebberling, Elke A.; Gillner, Arnold

    2003-11-01

    In the production of micro devices for applications in chemistry, biotechnology and medical technologies surface properties become more and more important. The microscale topography and surface chemistry have influence on wetting properties and cell behavior. Therefore the design of material surface determines the success of artificial devices in contact with biological systems. For applications in the field of medical implants laser technologies have been developed for micro structuring of polymers to modify the surface properties with respect to wettability and controlled cell growth. The technology is based on excimer laser treatment of polymer surfaces using laser wavelength 193 nm (ArF) with different fluences and cumulated energies. Depending on the processing parameters and examined polymers either hydrophobic or hydrophilic surfaces can be increased. The water contact angle of polydimethylsiloxane (PDMS) for example can be increased from 113° to approx. 150° so that the surface exhibits the so called lotus effect. The laser generated micro patterns reveal influence on cell density and cell distribution which can be used for cell guidance. Results for cell growing experiments are shown for different polymers.

  1. Structural and optical modifications in gamma-irradiated polyimide/silica nanocomposite

    Science.gov (United States)

    Nouh, S. A.; Tommalieh, M. J.; El-Shamy, N. T.

    2015-06-01

    The structural and optical properties of thin films of polyimide composites with nanosilica particle content of 15 wt%, prepared via sol-gel process, were studied as a function of the gamma dose. The resultant effect of gamma irradiation on the properties of polyimide/silica nanocomposite has been investigated using X-ray diffraction and UV spectroscopy. Absorption and reflectance spectra were collected by a spectrophotometer giving UV-radiation of wavelength range 200-800 nm. The optical data obtained were analyzed and the calculated values of the optical energy gap exhibited gamma dose dependence. The direct optical energy gap for the nonirradiated polyimide/silica nanocomposite is about 2.41 eV, and increases to a value of 2.65 eV when irradiated with gamma doses up to 300 kGy. It was found that the calculated refractive index of the polyamide/silica increases with the gamma dose in the range 50-300 kGy.

  2. Vacuum structure in a chiral $R+R^n$ modification of pure supergravity

    CERN Document Server

    Ferrara, Sergio; Porrati, Massimo

    2013-01-01

    We discuss an ${\\cal R}+{\\cal R}^n$ class of modified ${\\cal N}=1$, D=4 supergravity models where the deformation is a monomial ${\\cal R}^n\\big|_F$ in the chiral scalar curvature multiplet ${\\cal R}$ of the "old minimal" auxiliary field formulation. The scalaron and goldstino multiplets are dual to each other in this theory. Since one of them is not dynamical, this theory, as recently shown, cannot be used as the supersymmetric completion of $R+R^n$ gravity. This is confirmed by investigating the scalar potential and its critical points in the dual standard supergravity formulation with a single chiral multiplet with specific K\\"ahler potential and superpotential. We study the vacuum structure of this dual theory and we find that there is always a supersymmetric Minkowski critical point which however is pathological for $n\\geq 3$ as it corresponds to a corner ($n=3$) and a cusp ($n>3$) point of the potential. For $n>3$ an anti-de Sitter regular supersymmetric vacuum emerges. As a result, this class of models ...

  3. Structural modification of unilamellar and multilamellar vesicles in the presence of vitamin D

    Science.gov (United States)

    Devarajan, A.; Raouf, Y. A.; Rashid, S.; Law, R. L.; Stojanoff, V.; Isakovic, A. F.; Gater, D. L.

    Chronic vitamin D deficiency is increasingly associated with a range of health conditions, such as cardiovascular disease, diabetes and certain cancers. Our report contributes to a mechanistic understanding of these associations. Vitamin D is a lipophilic compound that is synthesized in the skin by the action of UV light on 7-dehydrocholesterol and obtained from dietary sources. We look at how vitamin D could be extracted from either skin membranes or therapeutic liposomes and transported through the body by its associated proteins. A variety of physical techniques (FTIR, DLS, UV-Vis spectroscopy, NMR, XRD) are brought to investigate: (a) the behavior of vitamin D in model membranes, and (b) the effect of vitamin D-associated proteins on membrane structure. Our results include: (1) vitamin D can be incorporated into DOPC membranes up to 40mol% with only minor changes in the dynamics of the lipid acyl chains; (2) liposomes containing larger quantities of vitamin D may have reduced stability over time; (3) the vitamin D binding protein and the vitamin D receptor do associate with and alter the behavior of model membranes, including systems that do not contain vitamin D. We acknowledge the support from KU-KAIST collaborative Grant program, and support from BNL staff.

  4. Structural and Chemical Characterization of Silica Spheres before and after Modification by Silanization for Trypsin Immobilization

    Directory of Open Access Journals (Sweden)

    Eduardo F. Barbosa

    2017-01-01

    Full Text Available In the last decades, silica particles of a variety of sizes and shapes have been characterized and chemically modified for several applications, from chromatographic separation to dental supplies. The present study proposes the use of aminopropyl triethoxysilane (APTS silanized silica particles to immobilize the proteolytic enzyme trypsin for the development of a bioreactor. The major advantage of the process is that it enables the polypeptides hydrolysis interruption simply by removing the silica particles from the reaction bottle. Silanized silica surfaces showed significant morphological changes at micro- and nanoscale level. Chemical characterization showed changes in elemental composition, chemical environment, and thermal degradation. Their application as supports for trypsin immobilization showed high immobilization efficiency at reduced immobilization times, combined with more acidic conditions. Indirect immobilization quantification by reversed-phase ultrafast high performance liquid chromatography proved to be a suitable approach due to its high linearity and sensitivity. Immobilized trypsin activities on nonmodified and silanized silica showed promising features (e.g., selective hydrolysis for applications in proteins/peptides primary structure elucidation for proteomics. Silanized silica system produced some preferential targeting peptides, probably due to the hydrophobicity of the nanoenvironment conditioned by silanization.

  5. Evolutive and structural characterization of Nostoc commune iron-superoxide dismutase that is fit for modification.

    Science.gov (United States)

    Ma, Y; Lu, M; Li, J-Y; Qin, Y; Gong, X-G

    2012-10-04

    Superoxide dismutase (SOD) has extensive clinical applications for protecting organisms from toxic oxidation. In this study, the integrated iron-superoxide dismutase gene (fe-sod) coding sequence of Nostoc commune stain CHEN was cloned from genomic DNA and compared to sods from other reported algae. These analyses of immunology and phylogenetics indicated that this Fe-SOD is considerably homologous with SODs from lower prokaryotes (Fe-SOD or Mn-SOD) but not those from higher animals (Cu/Zn-SOD). In addition, the N. commune Fe-SOD shows 67 to 93% protein sequence identity to 10 other algal Fe-SODs (or Mn-SODs) and 69 to 93% gene sequence identity. Rare nonsynonymous substitutions imply that algal SODs are being subjected to strong natural selection. Interestingly, the N. commune Fe-SOD enzyme molecule has a compact active center that is highly conserved (38.1% of residues are absolutely conserved), and 2 loose ends localized outside the molecule and inclined to mutate (only 11.5% of residues are absolutely conserved). Based on associative analyses of evolution, structure, and function, this special phenomenon is attributed to function-dependent evolution through negative natural selection. Under strong natural selection, although the mutation is random on the gene level, the exterior region is inclined to mutate on the protein level owing to more nonsynonymous substitutions in the exterior region, which demonstrates the theoretical feasibility of modifying Fe-SOD on its ends to overcome its disadvantages in clinical applications.

  6. Modification in structure, phase transition, and magnetic property of metallic gallium driven by atom-molecule interactions.

    Science.gov (United States)

    Song, Le Xin; Chen, Jie; Zhu, Lin Hong; Xia, Juan; Yang, Jun

    2011-09-05

    The present work supports a novel paradigm in which the surface structure and stacking behavior of metallic gallium (Ga) were significantly influenced by the preparation process in the presence of organic small molecules (ethanol, acetone, dichloromethane, and diethyl ether). The extent of the effect strongly depends on the polarity of the molecules. Especially, a series of new atom-molecule aggregates consisting of metallic Ga and macrocyclic hosts (cyclodextrins, CDs) were prepared and characterized by various techniques. A comprehensive comparative analysis between free metallic Ga and the Ga samples obtained provides important and at present rare information on the modification in structure, phase transition, and magnetic property of Ga driven by atom-molecule interactions. First, there is a notable difference in microstructure and electronic structure between the different types of Ga samples. Second, differential scanning calorimetry analysis gives us a complete picture (such as the occurrence of a series of metastable phases of Ga in the presence of CDs) that has allowed us to consider that Ga atoms were protected by the shielding effect provided by the cavities of CDs. Third, the metallic Ga distributed in the aggregates exhibits very interesting magnetic property compared to free metallic Ga, such as the uniform zero-field-cooled and field-cooled magnetization processes, the enhanced responses in magnetization to temperature and applied field, and the fundamental change in shape of magnetic hysteresis loops. These significant changes in structural transformation and physical property of Ga provide a novel insight into the understanding of atom-molecule interactions between metallic atoms and organic molecules.

  7. Modifications in structural, cation distribution and magnetic properties of {sup 60}Co gamma irradiated Li-ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Mane, Maheshkumar L. [Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad (M.S.) 431 004 (India); Shirsath, Sagar E., E-mail: shirsathsagar@hotmail.com [Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad (M.S.) 431 004 (India); Dhage, Vinod N.; Jadhav, K.M. [Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad (M.S.) 431 004 (India)

    2011-09-15

    Highlights: {yields} Gamma irradiation induced defects in lithium ferrite. {yields} Modifications in structural and magnetic properties. {yields} Fe{sup 3+} changes to Fe{sup 2+} after gamma irradiation. - Abstract: Polycrystalline samples of Li{sub 0.5}Fe{sub 2.5}O{sub 4} ferrite precursor were prepared by conventional standard double sintering ceramic technique and then irradiated with three different doses of {sup 60}Co gamma rays. The crystal structure and phase orientation of the irradiated and unirradiated samples of Li{sub 0.5}Fe{sub 2.5}O{sub 4} ferrite was done by using X-ray diffraction technique at room temperature. The lattice parameter of the studied samples increased due to the formation of Fe{sup 2+} ions under the ionizing effect of gamma radiation. The strain in the materials due to the irradiation was calculated from XRD data. Scanning electron microscope (SEM) studies indicate that the irradiation causes amorphization, especially at the grain boundaries. The cation distribution was calculated from XRD data analysis. By using cation distribution structural parameters such as theoretical lattice constant, ionic radii of available sites and the oxygen parameter 'u' have been calculated. The estimated cation distribution and other structural parameters shows strong influence of gamma rays on polycrystalline Li-ferrite. The magnetic properties of irradiated and unirradiated lithium ferrite were performed by using pulse field hysteresis loop technique at room temperature. Electrical properties such as diffusion coefficient and dielectric properties were carried out with the influence of gamma irradiation. Activation energy of diffusion process decreased after irradiation. The increase of diffusion coefficient with increasing dose rate of gamma irradiation was reinforced by the increase of Fe{sup 2+} ions and the displacement of metal ions from its original sites under the effect of gamma irradiation.

  8. Scanning electron microscopic investigations of root structural modifications arising from growth in crude oil-contaminated sand.

    Science.gov (United States)

    Balasubramaniyam, Anuluxshy; Harvey, Patricia J

    2014-11-01

    The choice of plant for phytoremediation success requires knowledge of how plants respond to contaminant exposure, especially their roots which are instrumental in supporting rhizosphere activity. In this study, we investigated the responses of plants with different architectures represented by beetroot (Beta vulgaris), a eudicot with a central taproot and many narrower lateral roots, and tall fescue (Festuca arundinacea), a monocot possessing a mass of threadlike fibrous roots to grow in crude oil-treated sand. In this paper, scanning electron microscopy was used to investigate modifications to plant root structure caused by growth in crude oil-contaminated sand. Root structural disorders were evident and included enhanced thickening in the endodermis, increased width of the root cortical zone and smaller diameter of xylem vessels. Inhibition in the rate of root elongation correlated with the increase in cell wall thickening and was dramatically pronounced in beetroot compared to the roots of treated fescue. The latter possessed significantly fewer (p root hairs compared to control plants. Possibly, root hairs that absorb the hydrophobic contaminants may prevent contaminant absorption into the main root and concomitant axile root thickening by being sloughed off from roots. Tall fescue exhibited greater root morphological adaptability to growth in crude oil-treated sand than beetroot and, thus, a potential for long-term phytoremediation.

  9. New catalyst supports prepared by surface modification of graphene- and carbon nanotube structures with nitrogen containing carbon coatings

    Science.gov (United States)

    Oh, Eun-Jin; Hempelmann, Rolf; Nica, Valentin; Radev, Ivan; Natter, Harald

    2017-02-01

    We present a new and facile method for preparation of nitrogen containing carbon coatings (NCC) on the surface of graphene- and carbon nanotubes (CNT), which has an increased electronic conductivity. The modified carbon system can be used as catalyst support for electrocatalytic applications, especially for polymer electrolyte membrane fuel cells (PEMFC). The surface modification is performed by impregnating carbon structures with a nitrogen containing ionic liquid (IL) with a defined C:N ratio, followed by a thermal treatment under ambient conditions. We investigate the influence of the main experimental parameters (IL amount, temperature, substrate morphology) on the formation of the NCC. Additionally, the structure and the chemical composition of the resulting products are analyzed by electron microscopic techniques (SEM, TEM), energy disperse X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS) and hot extraction analysis. The modified surface has a nitrogen content of 29 wt% which decreases strongly at temperatures above 600 °C. The new catalyst supports are used for the preparation of PEMFC anodes which are characterized by polarization measurements and electrochemical impedance spectroscopy (EIS). Compared to unmodified graphene and CNT samples the electronic conductivity of the modified systems is increased by a factor of 2 and shows improved mass transport properties.

  10. Simultaneous improvement in productivity, water use, and albedo through crop structural modification.

    Science.gov (United States)

    Drewry, Darren T; Kumar, Praveen; Long, Stephen P

    2014-06-01

    Spanning 15% of the global ice-free terrestrial surface, agricultural lands provide an immense and near-term opportunity to address climate change, food, and water security challenges. Through the computationally informed breeding of canopy structural traits away from those of modern cultivars, we show that solutions exist that increase productivity and water use efficiency, while increasing land-surface reflectivity to offset greenhouse gas warming. Plants have evolved to maximize capture of radiation in the upper leaves, thus shading competitors. While important for survival in the wild, this is suboptimal in monoculture crop fields for maximizing productivity and other biogeophysical services. Crop progenitors evolved over the last 25 million years in an atmosphere with less than half the [CO2] projected for 2050. By altering leaf photosynthetic rates, rising [CO2] and temperature may also alter the optimal canopy form. Here using soybean, the world's most important protein crop, as an example we show by applying optimization routines to a micrometeorological leaf canopy model linked to a steady-state model of photosynthesis, that significant gains in production, water use, and reflectivity are possible with no additional demand on resources. By modifying total canopy leaf area, its vertical profile and angular distribution, and shortwave radiation reflectivity, all traits available in most major crop germplasm collections, increases in productivity (7%) are possible with no change in water use or albedo. Alternatively, improvements in water use (13%) or albedo (34%) can likewise be made with no loss of productivity, under Corn Belt climate conditions. © 2014 California Institute of Technology. Government sponsorship acknowledged.

  11. BaCO3 mediated modifications in structural and magnetic properties of natural nanoferrites

    Science.gov (United States)

    Widanarto, W.; Jandra, M.; Ghoshal, S. K.; Effendi, M.; Cahyanto, W. T.

    2015-04-01

    Preparing M-type barium hexaferrite and improving the magnetic response of natural ferrites by incorporating barium carbonate (BaCO3) is ever-demanding. Series of barium carbonate doped ferrites with composition (100-x)Fe3O4·xBaCO3 (x=0, 10, 20, 30 wt%) are prepared through solid state reaction method and sintered gradually at temperatures of 800 and 1000 °C. Nanoparticles of natural ferrite and commercial BaCO3 are used as raw materials. Impacts of BaCO3 on structural and magnetic properties of these synthesized ferrites are inspected. The obtained ferrites are characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM) at room temperature. Uniform barium hexaferrite particles in terms of both morphology and size are not achieved. The average crystallite size of BaFe12O19 is observed to be within 30-600 nm. The sintering process results phase transformation from Fe3O4 (magnetite) to α-Fe2O3 (hematite) and the formation of hexagonal barium ferrite crystals. The occurrence of barium crystal is found to enhance with the increase of BaCO3 concentrations up to 20 wt% and suddenly drop at 30 wt%. Saturation and remanent magnetization of the doped ferrites are significantly augmented up to 16.37 and 8.92 emu g-1, respectively compared to their pure counterpart. Furthermore, the coercivity field is slightly decreased as BaCO3 concentrations are increased. BaCO3 mediated improvements in the magnetic response of natural ferrites are demonstrated.

  12. Structure-immunosuppressive activity relationships of new analogues of 15-deoxyspergualin. 2. Structural modifications of the spermidine moiety.

    Science.gov (United States)

    Lebreton, L; Jost, E; Carboni, B; Annat, J; Vaultier, M; Dutartre, P; Renaut, P

    1999-11-18

    A series of new analogues of 15-deoxyspergualin (DSG), an immunosuppressive agent commercialized in Japan, was synthesized and tested in a graft-versus-host disease (GVHD) model in mice. Various substitutions of the spermidine "D" region were made in order to determine its optimum structure in terms of in vivo immunosuppressive activity. Various positions of methylation were first investigated leading to the discovery of the monomethylated malonic derivative 56h in which the pro-R hydrogen of the methylene alpha to the primary amine of the spermidine moiety has been replaced by a methyl group. Synthesis of the similarly methylated analogue of the previously reported glycolic derivative LF 08-0299 afforded 60e which demonstrated a powerful activity at a dose as low as 0.3 mg/kg in the GVHD model and was much more potent than DSG in the demanding heart allotransplantation model in rats. The improvement of in vivo activity was supposed to be related to an increase of the metabolic stability of the methylated analogues compared to the parent molecules. Due to its very low active dose, compatible with a subcutaneous administration in humans, and its favorable pharmacological and toxicological profile, 60e was selected as a candidate for clinical evaluation.

  13. Proceedings of the 2nd joint seminar on atomic collisions and heavy ion induced nuclear reactions

    International Nuclear Information System (INIS)

    Harada, Kichinosuke; Ozawa, Kunio; Kamitsubo, H.; Nomura, T.; Awaya, Y.; Watanabe, T.

    1982-11-01

    The meeting of the 2nd joint seminar on atomic collisions and heavy ion induced nuclear reactions was held at the University of Tokyo, May 13 and 14, 1982. The aim of this seminar has been not only to recognize the common problems lying between above two research fields, but also to obtain an overview of the theoretical and experimental approaches to clear the current problems. In the seminar, more than 50 participants gathered and presented 16 papers. These are two general reviews and fourteen comprehensive surveys on topical subjects which have been developed very intensively in recent years. The editors would like to thank all participants for their assistance and cooperation in making possible a publication of these proceedings. (author)

  14. Determination of low-energy ion-induced electron yields from thin carbon foils

    International Nuclear Information System (INIS)

    Allegrini, Frederic; Wimmer-Schweingruber, Robert F.; Wurz, Peter; Bochsler, Peter

    2003-01-01

    Ion beams crossing thin carbon foils can cause electron emission from the entrance and exit surface. Thin carbon foils are used in various types of time-of-flight (TOF) mass spectrometers to produce start pulses for TOF measurements. The yield of emitted electrons depends, among other parameters, on the energy of the incoming ion and its mass, and it has been experimentally determined for a few projectile elements. The electron emission yield is of great importance for deriving abundance ratios of elements and isotopes in space plasmas using TOF mass spectrometers. We have developed a detector for measuring ion-induced electron yields, and we have extended the electron yield measurements for oxygen to energies relevant for solar wind research. We also present first measurements of the carbon foil electron emission yield for argon and iron in the solar wind energy range

  15. Fragment formation in GeV-energy proton and light heavy-ion induced reactions

    International Nuclear Information System (INIS)

    Murakami, T.; Haga, M.; Haseno, M.

    2002-01-01

    We have investigated similarities and differences among the fragment formation processes in GeV-energy light-ion and light heavy-ion induced reactions. We have newly measured inclusive and exclusive energy spectra of intermediate mass fragments (3 ≤ Z ≤ 30; IMFs) for 8-GeV 16 O and 20 Ne and 12-GeV 20 Ne induced target multifragmentations (TMFs) in order to compare them with those previously measured for 8- and 12-GeV proton induced TMFs. We fond noticeable difference in their spectrum shapes and magnitudes but all of them clearly indicate the existence of sideward-peaked components, indicating fragment formations are mainly dictated not by a incident energy per nucleon but by a total energy of the projectile. (author)

  16. In-situ investigations of surface modifications by swift heavy ions

    International Nuclear Information System (INIS)

    Bolse, W.; Sankarakumar, A.; Ferhati, R.; Garmatter, D.; Haag, M.; Dautel, K.; Asdi, M.; Srivastava, N.; Widmann, B.; Bauer, M.

    2014-01-01

    We are running a High Resolution Scanning Electron Microscope in the beam line of the UNILAC ion accelerator at the GSI Helmholtz Centre for Heavy Ion Research in Danustadt, Germany, which has recently been extended also with an EDX-system and two micro-manipulators. This instrument allows us to in-situ investigate the structural and compositional development of individual objects and structures in the μm- and nm-range under swift heavy ion bombardment, from the very first ion impact up to high fluences of the order of several 10 15 /cm 2 . The sample under investigation is irradiated in small fluence steps and in between SEM-images (and EDX-scans) of one and the same surface area are taken. The irradiation can be carried out at any incidence angle between 0° and 90° and also under stepwise or continuous azimuthal rotation of the sample. The micro-manipulator system allows us to perform additional analysis like electrical and mechanical characterization as well as substrate-free EDX at sub-μm objects. We are now also able to irradiate almost free standing sub-μm structures (pasted on a nanoscale tip or held in micro-tweezers). In this report an overview over this unique instrument and its capabilities and advantages will be given, illustrated by the results of our recent in-situ studies on ion induced modification of thin films (dewetting and self-organisation) and on shaping of sub-μm objects with swift heavy ions (by taking advantage of ion sputtering, ion hammering and ion induced visco-elastic flow). (author)

  17. Potential for ion-induced nucleation of volatile organic compounds by radon decay in indoor environments

    International Nuclear Information System (INIS)

    Daisey, J.M.

    1991-11-01

    There is considerable interest in the ''unattached'' fraction of radon progeny in indoor air because of its significance to the estimation of the risks of radon exposure. Because of its high mobility in air, the unattached fraction is more efficiently deposited in the respiratory tract. Variation in the diameter of the ''unattached'' fraction and in its diffusion coefficient can be due to clustering of other atmospheric species around the 218 PoO 2 + ion. The purpose of this study was to investigate the potential for the formation of clusters of vapor phase organic compounds, found in indoor air, around the 218 PoO 2 + ion and to determine which were most likely to form clusters. A secondary purpose was to provide a compilation of measurements of indoor organic compounds for future experiments and theoretical calculations by the radon research community. The classical charged liquid droplet theory (Thomson equation) was used to estimate the Gibbs free energy of ion-induced nucleation and to provide an indication of the indoor organic compounds most likely to undergo ion-induced nucleation. Forty-four volatile and semi-volatile organic compounds out of the more than 300 which have been reported in indoor air were investigated. Water vapor was included for comparison. The results indicate that there is a potential for the formation of clusters of organic compounds around the 218 PoO 2 + ion. The compounds with the greatest potential for cluster formation are the volatile oxidized hydrocarbons (e.g., n-butanol, phenol, hexanal, nonanal, benzaldehyde, the ketones and the acetates) and the semi-volatile organic compounds (pentachlorophenol, nicotine, chlordane, chlorpyrifos)

  18. Lipid A structural modifications in extreme conditions and identification of unique modifying enzymes to define the Toll-like receptor 4 structure-activity relationship.

    Science.gov (United States)

    Scott, Alison J; Oyler, Benjamin L; Goodlett, David R; Ernst, Robert K

    2017-11-01

    Strategies utilizing Toll-like receptor 4 (TLR4) agonists for treatment of cancer, infectious diseases, and other targets report promising results. Potent TLR4 antagonists are also gaining attention as therapeutic leads. Though some principles for TLR4 modulation by lipid A have been described, a thorough understanding of the structure-activity relationship (SAR) is lacking. Only through a complete definition of lipid A-TLR4 SAR is it possible to predict TLR4 signaling effects of discrete lipid A structures, rendering them more pharmacologically relevant. A limited 'toolbox' of lipid A-modifying enzymes has been defined and is largely composed of enzymes from mesophile human and zoonotic pathogens. Expansion of this 'toolbox' will result from extending the search into lipid A biosynthesis and modification by bacteria living at the extremes. Here, we review the fundamentals of lipid A structure, advances in lipid A uses in TLR4 modulation, and the search for novel lipid A-modifying systems in extremophile bacteria. This article is part of a Special Issue entitled: Bacterial Lipids edited by Russell E. Bishop. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Competition between surface modification and abrasive polishing: a method of controlling the surface atomic structure of 4H-SiC (0001)

    Science.gov (United States)

    Deng, Hui; Endo, Katsuyoshi; Yamamura, Kazuya

    2015-03-01

    The surface atomic step-terrace structure of 4H-SiC greatly affects its performance in power device applications. On the basis of the crystal structure of 4H-SiC, we propose the generation mechanism of the a-b-a*-b* type, a-b type and a-a type step-terrace structures. We demonstrate that the step-terrace structure of SiC can be controlled by adjusting the balance between chemical modification and physical removal in CeO2 slurry polishing. When chemical modification plays the main role in the polishing of SiC, the a-b-a*-b* type step-terrace structure can be generated. When the roles of physical removal and chemical modification have similar importance, the a-b-a*-b* type step-terrace structure changes to the a-b type. When physical removal is dominant, the uniform a-a type step-terrace structure can be generated.

  20. Prenylated flavonoids as potent phosphodiesterase-4 inhibitors from Morus alba: Isolation, modification, and structure-activity relationship study.

    Science.gov (United States)

    Guo, Yan-Qiong; Tang, Gui-Hua; Lou, Lan-Lan; Li, Wei; Zhang, Bei; Liu, Bo; Yin, Sheng

    2018-01-20

    The bioassay-guided phytochemical study of a traditional Chinese medicine Morus alba led to the isolation of 18 prenylated flavonoids (1-18), of which (±)-cyclomorusin (1/2), a pair of enantiomers, and 14-methoxy-dihydromorusin (3) are the new ones. Subsequent structural modification of the selected components by methylation, esterification, hydrogenation, and oxidative cyclization led to 14 more derivatives (19-32). The small library was screened for its inhibition against phosphodiesterase-4 (PDE4), which is a drug target for the treatment of asthma and chronic obstructive pulmonary disease (COPD). Among them, nine compounds (1-5, 8, 10, 16, and 17) exhibited remarkable activities with IC 50 values ranging from 0.0054 to 0.40 μM, being more active than the positive control rolipram (IC 50  = 0.62 μM). (+)-Cyclomorusin (1), the most active natural PDE4 inhibitor reported so far, also showed a high selectivity across other PDE members with the selective fold greater than 55. The SAR study revealed that the presence of prenyls at C-3 and/or C-8, 2H-pyran ring D, and the phenolic hydroxyl groups were important to the activity, which was further supported by the recognition mechanism study of the inhibitors with PDE4 by using molecular modeling. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  1. Modifications of structural, chemical, and electrical characteristics of Er2O3/Si interface under Co-60 gamma irradiation

    Science.gov (United States)

    Kaya, Senol; Yilmaz, Ercan

    2018-03-01

    This paper reports the influences of gamma radiation on the structural, electrical, and chemical characteristics of erbium oxide (Er2O3) thin films and the possible mechanisms underlying these irradiation-induced effects. The crystallographic and morphological modifications under gamma irradiation were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively, while radiation influences on electrochemical characteristics were analyzed by X-ray photoelectron spectroscopy (XPS). Furthermore, changes in electrical characteristics were analyzed on the basis of capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements. The XRD results demonstrated that small atomic displacement was observed and that the grain size of the nanostructure slightly increased. Improvements in surface roughness were observed in AFM measurements. The observed variations in the XRD and AFM measurements can be attributed to the radiation-induced local heating and microscopic atomic mobility. In addition, the XPS analysis obviously demonstrated that the oxygen vacancies increased with irradiation dose because of the breaking of Er2O3 and ErxOy bonds. Significant influences of the generated oxygen vacancies on the electrical measurements were observed, and the radiation-induced hole traps, which caused large flat band shifts, can be attributed to the generated oxygen vacancies. The results show that radiation does not degrade the physical characteristics significantly, but the generation of oxygen vacancies considerably increases the electrical sensitivity of the Er2O3 dielectric.

  2. Down-regulation of an Auxin Response Factor in the tomato induces modification of fine pectin structure and tissue architecture.

    Science.gov (United States)

    Guillon, Fabienne; Philippe, Sully; Bouchet, Brigitte; Devaux, Marie-Françoise; Frasse, Pierre; Jones, Brian; Bouzayen, Mondher; Lahaye, Marc

    2008-01-01

    It has previously been shown that down-regulation of an auxin response factor gene (DR12) results in pleiotropic phenotypes including enhanced fruit firmness in antisense transgenic tomato (AS-DR12). To uncover the nature of the ripening-associated modifications affecting fruit texture, comparative analyses were performed of pectin composition and structure in cell wall pericarp tissue of wild-type and AS-DR12 fruit at mature green (MG) and red-ripe (RR) stages. Throughout ripening, pectin showed a decrease in methyl esterification and in the content of galactan side chains in both genotypes. At mature green stage, pectin content in methyl ester groups was slightly higher in AS-DR12 fruit than in wild type, but this ratio was reversed at the red-ripe stage. The amount of water- and oxalate-soluble pectins increased at the red-ripe stage in the wild type, but decreased in AS-DR12. The distribution of methyl ester groups on the homogalaturonan backbone differed between the two genotypes. There was no evidence of more calcium cross-linked homogalacturan involved in cell-to-cell adhesion in AS-DR12 compared with wild-type fruit. Furthermore, the outer pericarp contains higher proportion of small cells in AS-DR12 fruit than in wild type and higher occurrence of (1-->5) alpha-L-arabinan epitope at the RR stage. It is concluded that the increased firmness of transgenic fruit does not result from a major impairment of ripening-related pectin metabolism, but rather involves differences in pectin fine structure associated with changes in tissue architecture.

  3. Class 1 Permit Modification Notification Addition of Structures within Technical Area 54, Area G, Pad 11, Dome 375 Los Alamos National Laboratory Hazardous Waste Facility Permit, July 2012

    Energy Technology Data Exchange (ETDEWEB)

    Vigil-Holterman, Luciana R. [Los Alamos National Laboratory; Lechel, Robert A. [Los Alamos National Laboratory

    2012-08-31

    The purpose of this letter is to notify the New Mexico Environment Department-Hazardous Waste Bureau (NMED-HWB) of a Class 1 Permit Modification to the Los Alamos National Laboratory (LANL) Hazardous Waste Facility Permit issued to the Department of Energy (DOE) and Los Alamos National Security, LLC (LANS) in November 2010. The modification adds structures to the container storage unit at Technical Area (TA) 54 Area G, Pad 11. Permit Section 3.1(3) requires that changes to the location of a structure that does not manage hazardous waste shall be changed within the Permit as a Class 1 modification without prior approval in accordance with Code of Federal Regulations, Title 40 (40 CFR), {section}270.42(a)(1). Structures have been added within Dome 375 located at TA-54, Area G, Pad 11 that will be used in support of waste management operations within Dome 375 and the modular panel containment structure located within Dome 375, but will not be used as waste management structures. The Class 1 Permit Modification revises Figure 36 in Attachment N, Figures; and Figure G.12-1 in Attachment G.12, Technical Area 54, Area G, Pad 11 Outdoor Container Storage Unit Closure Plan. Descriptions of the structures have also been added to Section A.4.2.9 in Attachment A, TA - Unit Descriptions; and Section 2.0 in Attachment G.12, Technical Area 54, Area G, Pad 11 Outdoor Container Storage Unit Closure Plan. Full description of the permit modification and the necessary changes are included in Enclosure 1. The modification has been prepared in accordance with 40 CFR {section}270.42(a)(l). This package includes this letter and an enclosure containing a description of the permit modification, text edits of the Permit sections, and the revised figures (collectively LA-UR-12-22808). Accordingly, a signed certification page is also enclosed. Three hard copies and one electronic copy of this submittal will be delivered to the NMED-HWB.

  4. Biophysical analysis of the effect of chemical modification by 4-oxononenal on the structure, stability, and function of binding immunoglobulin protein (BiP.

    Directory of Open Access Journals (Sweden)

    Dinen D Shah

    Full Text Available Binding immunoglobulin protein (BiP is a molecular chaperone important for the folding of numerous proteins, which include millions of immunoglobulins in human body. It also plays a key role in the unfolded protein response (UPR in the endoplasmic reticulum. Free radical generation is a common phenomenon that occurs in cells under healthy as well as under stress conditions such as ageing, inflammation, alcohol consumption, and smoking. These free radicals attack the cell membranes and generate highly reactive lipid peroxidation products such as 4-oxononenal (4-ONE. BiP is a key protein that is modified by 4-ONE. In this study, we probed how such chemical modification affects the biophysical properties of BiP. Upon modification, BiP shows significant tertiary structural changes with no changes in its secondary structure. The protein loses its thermodynamic stability, particularly, that of the nucleotide binding domain (NBD where ATP binds. In terms of function, the modified BiP completely loses its ATPase activity with decreased ATP binding affinity. However, modified BiP retains its immunoglobulin binding function and its chaperone activity of suppressing non-specific protein aggregation. These results indicate that 4-ONE modification can significantly affect the structure-function of key proteins such as BiP involved in cellular pathways, and provide a molecular basis for how chemical modifications can result in the failure of quality control mechanisms inside the cell.

  5. Antimicrobial and antifungal activity of 2-(1H-tetrazolo-5-ylanilines and products of their structural modifications

    Directory of Open Access Journals (Sweden)

    O. M. Antypenko

    2016-08-01

    Full Text Available Virtually any molecule of antibiotic can be inactivated in the microbial cell by particular resistance mechanism. In this regard, each antibiotic effectiveness starts to decrease, which necessitates the synthesis of new antimicrobial agents. Aim. To examine the previously synthesized substituted 2-(1H-tetrazolo-5-ylanilines and products of their structural modification for antimicrobial and antifungal activity. Materials and methods. The study of biological activity was conducted by disco-diffusion method on Mueller-Hinton agar on these strains of microorganisms: Gram-positive cocci (Staphylococcus aureus ATCC 25923, Enterococcus aeruginosa, E. faecalis ATCC 29212, Gram-negative bacteria (Pseudomonas aeruginosa PSS27853, Escherichia coli ATCC 25922, facultative anaerobic gram-negative bacteria (Klebsiella pneumonia and fungi (Candida albicans ATCC 885653. Results. The studies showed, that the antifungal activity was characteristic only for S-substituted of tetrazolo[1,5-c]quinazoline-(6H-5-ones(thiones. The growth of gram-positive cocci Staphylococcus aureus and Enterococcus faecalis, more effectively detained 5-(N,N-dialkylaminoethylthio-tetrazolo[1,5-c]quinazolines (4.4-4.6. 1-(2- (1H-tetrazolo-5-yl-R1-phenyl-3-R2-phenyl(ethylureas (2.1-2.31 were more selective against Staphylococcus aureus and Enterococcus faecalis. Analysis of «structure-activity relationship» showed, that the introduction of halogen to the aniline fragment leads to increase of activity. Thus, the compound 2.3 with fluorine stopped the growth of Escherichia coli and Klebsiella pneumonia for 31 mm and 21 mm, respectively. Structures with chlorine (2.4 and bromine (2.5 stopped the growth of Pseudomonas aeruginosa at 20 mm and 23 mm, respectively. And the presence of trifluoromethyl group in the phenylureide fragment and chlorine in aniline fragment of compound 2.27 led to the highest growth delay zone 25 mm. Among the investigated compounds only 1-(4-methoxyphenyl-2

  6. Structural and electrochemical characterization and surface modification of layered solid solution oxide cathodes of lithium ion batteries

    Science.gov (United States)

    Wu, Yan

    Lithium ion batteries are widely used to power portable electronic devices such as cell phones and laptop computers due to their high energy density. However, the currently used layered LiCoO2 cathode could deliver only 50 % of its theoretical capacity in practical lithium ion cells (140 mAh/g) due to the chemical and structural instabilities at deep charge with (1-x) first charge and discharge capacity) values (up to 100 mAh/g), which have been reduced significantly by modifying the cathode surface with other materials like Al2O3, AlPO 4, and F-. For example, compared to an IRC of 75 mAh/g and a first discharge capacity of 253 mAh/g for the pristine Li[Li0.2 Mn0.54Ni0.13Co0.13]O2 (y = 1/6 and z = 0.4), the 3 wt. % Al2O3 modified sample exhibits a lower IRC of 41 mAh/g and a higher first discharge capacity of 285 mAh/g, which is two times higher than that achieved with the LiCoO 2 cathode. A careful and systematic analysis of the experimentally observed capacity and IRC values suggest that part of the oxide ion vacancies created during first charge is retained in the layered lattice in contrast to the idealized model (elimination of all oxide ion vacancies) proposed in the literature. The surface modification helps to retain even more number of oxide ion vacancies in the lattice, which leads to a lower IRC and higher discharge capacity values. Additionally, bulk cationic and anionic substitutions of Al3+ and F- in Li[Li0.17Mn0.58Ni0.25 ]O2 (y = 0 and z = 0.5) are found to sensitively decrease the amount of oxygen loss from the lattice.

  7. A trimeric structural fusion of an antagonistic tumor necrosis factor-α mutant enhances molecular stability and enables facile modification.

    Science.gov (United States)

    Inoue, Masaki; Ando, Daisuke; Kamada, Haruhiko; Taki, Shintaro; Niiyama, Mayumi; Mukai, Yohei; Tadokoro, Takashi; Maenaka, Katsumi; Nakayama, Taisuke; Kado, Yuji; Inoue, Tsuyoshi; Tsutsumi, Yasuo; Tsunoda, Shin-Ichi

    2017-04-21

    Tumor necrosis factor-α (TNF) exerts its biological effect through two types of receptors, p55 TNF receptor (TNFR1) and p75 TNF receptor (TNFR2). An inflammatory response is known to be induced mainly by TNFR1, whereas an anti-inflammatory reaction is thought to be mediated by TNFR2 in some autoimmune diseases. We have been investigating the use of an antagonistic TNF mutant (TNFR1-selective antagonistic TNF mutant (R1antTNF)) to reveal the pharmacological effect of TNFR1-selective inhibition as a new therapeutic modality. Here, we aimed to further improve and optimize the activity and behavior of this mutant protein both in vitro and in vivo Specifically, we examined a trimeric structural fusion of R1antTNF, formed via the introduction of short peptide linkers, as a strategy to enhance bioactivity and molecular stability. By comparative analysis with R1antTNF, the trimeric fusion, referred to as single-chain R1antTNF (scR1antTNF), was found to retain in vitro molecular properties of receptor selectivity and antagonistic activity but displayed a marked increase in thermal stability. The residence time of scR1antTNF in vivo was also significantly prolonged. Furthermore, molecular modification using polyethylene glycol (PEG) was easily controlled by limiting the number of reactive sites. Taken together, our findings show that scR1antTNF displays enhanced molecular stability while maintaining biological activity compared with R1antTNF. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  8. Heavy-ion-induced luminescence of amorphous SiO2 during nanoparticle formation

    International Nuclear Information System (INIS)

    Bandourko, Vassili; Umeda, Naoki; Plaksin, Oleg; Kishimoto, Naoki

    2005-01-01

    Silica glass was implanted with negative 60 keV Cu ions at an ion flux from 5 to 75 μA/cm 2 up to a fluence of 1 x 10 17 ions/cm 2 at initial sample temperatures of 300, 573 and 773 K. Spectra of ion-induced photon emission (IIPE) were collected in situ in the range from 250 to 850 nm. Optical absorption spectra of implanted specimens were ex situ measured in the range from 190 to 2500 nm. IIPE spectra showed a broad band centered around 560 nm (2.2 eV) that was assigned to Cu + solutes. The band appeared at the onset of irradiation, increased in intensity up to a fluence of about 5 x 10 15 ions/cm 2 and then gradually decreased indicating three stage of the ion beam synthesis of nanoclusters: accumulation of implants, nucleation and growth nanoclusters. The IIPE intensity normalized on the ion flux is independent on the ion flux below 20 μA/cm 2 at higher fluences. The intensity of the band increased with increasing samples temperature, when optical absorption spectra reveal the increase of Cu nanoparticles size

  9. Low energy ion induced desorption on technical surfaces at room temperature

    CERN Document Server

    Hulla, Georg

    2009-01-01

    The ion-induced pressure instability is a hard limitation for the maximum intensity, and hence the ultimate luminosity achievable in a proton accelerator. This instability is due to the interaction of high intensity proton beams with the residual gas generating positive ions. These ions, accelerated by the beam space charge, impact on the vaccuum chamber wall and lead to the desorption of gaseous species like $H_{2}, CH_{4}, C_{2}H_{4}, C_{2}H_{6}, CO$ and $CO_{2}$. These gases can in turn be ionized by the circulating beam, and initiate a pressure run-away process causing the loss of the stored beam. This phenomenon was first registered right at the beginning of operation of the Intersecting Storage Rings (ISR) at CERN in 1970. Later on, a long term evolution of the pressure was recorded for a stable stored beam current where a change of the residual gas composition was measured. In order to adapt the pumping speed and the surface treatments to the desired circulating beam currents, mathematical tools (e.g. ...

  10. Heavy-ion-induced production and preseparation of short-livedisotopes for chemistry experiments

    Energy Technology Data Exchange (ETDEWEB)

    Dullmann, Christoph E.; Folden III, Charles M.; Gregorich, Kenneth E.; Hoffman, Darleane C.; Leitner, Daniela; Pang, Gregory K.; Sudowe, Ralf; Zielinski, Peter M.; Nitsche, Heino

    2005-02-24

    Physical separation of short-lived isotopes produced inheavy-ion-induced fusion reactions is a powerful and well know method andoften applied in investigations of the heaviest elements, called thetransactinides (Z>=104). By extracting these isotopes from a recoilseparator, they can be made available for transport to setups locatedoutside the heavily shielded irradiation position such as chemistrysetups. This physical preseparation technique overcomes many limitationscurrently faced in the chemical investigation of transactinides. Here wedescribe the basic principle using relatively short-lived isotopes of thelighter group 4 elements zirconium (Zr) and hafnium (Hf) that are used asanalogs of the lightest transactinide element, rutherfordium (Rf, element104). The Zr and Hf isotopes were produced at the LBNL 88-Inch Cyclotronusing a cocktail of 18O and 50Ti beams and the appropriate targets.Subsequently, the isotopes were physically separated in the BerkeleyGas-filled Separator (BGS) and guided to a Recoil Transfer Chamber (RTC)to transfer them to chemistry setups. The magnetic rigidities of thereaction products in low-pressure helium gas were measured and theiridentities determined with gamma-pectroscopy. Using preseparated isotopeshas the advantages of low background and beam plasma free environment forchemistry experiments. The new possibilities that open up for chemicalinvestigations of transactinide elements are descr ibed. The method canreadily be applied to homologous elements within other groups in theperiodic table.

  11. Review of Heavy-ion Induced Desorption Studies for Particle Accelerators

    CERN Document Server

    Mahner, E

    2008-01-01

    During high-intensity heavy-ion operation of several particle accelerators worldwide, large dynamic pressure rises of orders of magnitude were caused by lost beam ions that impacted under grazing angle onto the vacuum chamber walls. This ion-induced desorption, observed, for example, at CERN, GSI, and BNL, can seriously limit the ion intensity, luminosity, and beam lifetime of the accelerator. For the heavyion program at CERN's Large Hadron Collider collisions between beams of fully stripped lead (208Pb82+) ions with a beam energy of 2.76 TeV/u and a nominal luminosity of 10**27 cm**-2 s**-1 are foreseen. The GSI future project FAIR (Facility for Antiproton and Ion Research) aims at a beam intensity of 10**12 uranium (238U28+) ions per second to be extracted from the synchrotron SIS18. Over the past years an experimental effort has been made to study the observed dynamic vacuum degradations, which are important to understand and overcome for present and future particle accelerators. The paper reviews the resu...

  12. The use of low energy, ion induced nuclear reactions for proton radiotherapy applications

    Science.gov (United States)

    Horn, K. M.; Doyle, B.; Segal, M. N.; Hamm, R. W.; Adler, R. J.; Glatstein, E.

    1995-12-01

    Medical radiotherapy has traditionally relied upon the use of external photon beams and internally implanted radioisotopes as the chief means of irradiating tumors. However, advances in accelerator technology and the exploitation of novel means of producing radiation may provide useful alternatives to some current modes of medical radiation delivery — with reduced total dose to surrounding healthy tissue, reduced expense, or increased treatment accessibility. This paper will briefly overview currently established modes of radiation therapy, techniques still considered experimental but in clinical use and innovative concepts under study that may enable new forms of treatment or enhance existing ones. The potential role of low energy, ion-induced nuclear reactions in radiotherapy applications is examined specifically for the 650 keV d( 3He,p) 4 He nuclear reaction. This examination will describe the basic physics associated with this reaction's production of 17.4 MeV protons and the processes used to fabricate the necessary materials used in the technique. Calculations of the delivered radiation dose, heat generation, and required exposure times are presented. Experimental data is also presented validating the dose calculations. The design of small, lower cost ion accelerators, as embodied in "nested"-tandem and radio frequency quadrupole accelerators is examined, as is the potential use of high-output 3He and deuterium ion sources. Finally, potential clinical applications are discussed in terms of the advantages and disadvantages of this technique with respect to current radiotherapy methods and equipment.

  13. Heavy ion induced fission between 10 and 100 MeV/u

    International Nuclear Information System (INIS)

    Steckmeyer, J.C.; Tamain, B.

    1986-05-01

    Heavy ion induced fission between 10 and 100 MeV/u is discussed. It is shown that one can obtain information on fusion limits and on typical times characterizing nuclear matter. Intermediate energy heavy ions can be used to build very excited fusion nuclei. Section I shows that fission can then be used as a tool to test the fusion mechanism and to discover what are the extreme limits concerning fusion and hot nuclei formation. In section II, it is shown that when very hot nuclei are built, fission evaporation competition cannot any longer be fully described in the usual way by the statistical model. New features as dynamical aspects or cluster evaporation modify dramatically the landscape. Concerning the detailed fission properties of very hot nuclei (for instance fragments properties), no strong deviations from the already know systematics has been obtained. However, very few detailed studies are yet available and a clear experimental program has to be developed in order to progress. From a theoretical point of view, it is rather necessary to described fission and evaporation is an unified way

  14. Parameterization of ion-induced nucleation rates based on ambient observations

    Directory of Open Access Journals (Sweden)

    T. Nieminen

    2011-04-01

    Full Text Available Atmospheric ions participate in the formation of new atmospheric aerosol particles, yet their exact role in this process has remained unclear. Here we derive a new simple parameterization for ion-induced nucleation or, more precisely, for the formation rate of charged 2-nm particles. The parameterization is semi-empirical in the sense that it is based on comprehensive results of one-year-long atmospheric cluster and particle measurements in the size range ~1–42 nm within the EUCAARI (European Integrated project on Aerosol Cloud Climate and Air Quality interactions project. Data from 12 field sites across Europe measured with different types of air ion and cluster mobility spectrometers were used in our analysis, with more in-depth analysis made using data from four stations with concomitant sulphuric acid measurements. The parameterization is given in two slightly different forms: a more accurate one that requires information on sulfuric acid and nucleating organic vapor concentrations, and a simpler one in which this information is replaced with the global radiation intensity. These new parameterizations are applicable to all large-scale atmospheric models containing size-resolved aerosol microphysics, and a scheme to calculate concentrations of sulphuric acid, condensing organic vapours and cluster ions.

  15. The use of low energy, ion induced nuclear reactions for proton radiotherapy applications

    International Nuclear Information System (INIS)

    Horn, K.M.; Doyle, B.; Segal, M.N.; Adler, R.J.; Glatstein, E.

    1995-01-01

    Medical radiotherapy has traditionally relied upon the use of external photon beams and internally implanted radioisotopes as the chief means of irradiating tumors. However, advances in accelerator technology and the exploitation of novel means of producing radiation may provide useful alternatives to some current modes of medical radiation delivery with reduced total dose to surrounding healthy tissue, reduced expense, or increased treatment accessibility. This paper will briefly overview currently established modes of radiation therapy, techniques still considered experimental but in clinical use, innovative concepts under study that may enable new forms of treatment or enhance existing ones. The potential role of low energy, ion-induced nuclear reactions in radiotherapy applications is examined specifically for the 650 keV d( 3 He,p) 4 He nuclear reaction. This examination will describe the basic physics associated with this reaction's production of 17.4 MeV protons and the processes used to fabricate the necessary materials used in the technique. Calculations of the delivered radiation dose, heat generation, and required exposure times are presented. Experimental data are also presented validating the dose calculations. The design of small, lower cost ion accelerators, as embodied in 'nested'-tandem and radio frequency quadrupole accelerators is examined, as is the potential use of high-output 3 He and deuterium ion sources. Finally, potential clinical applications are discussed in terms of the advantages and disadvantages of this technique with respect to current radiotherapy methods and equipment

  16. Flash thermal conditioning of olive pastes during the olive oil mechanical extraction process: impact on the structural modifications of pastes and oil quality.

    Science.gov (United States)

    Esposto, Sonia; Veneziani, Gianluca; Taticchi, Agnese; Selvaggini, Roberto; Urbani, Stefania; Di Maio, Ilona; Sordini, Beatrice; Minnocci, Antonio; Sebastiani, Luca; Servili, Maurizio

    2013-05-22

    The quality of virgin olive oil (VOO) is strictly related to the concentrations of phenolic and volatile compounds, which are strongly affected by the operative conditions of the VOO mechanical extraction process. The aim of this work is to study the impact of a new technology such as flash thermal conditioning (FTC) on olive paste structural modification and on VOO quality. The evaluation of olive paste structure modification by cryo-scanning electron microscopy (cryo-SEM) showed that the application of FTC after crushing produces significant differences in terms of the breaking of the parenchyma cells and aggregation of oil droplets in comparison to the crushed pastes. The virgin olive oil flash thermal conditioning (VOO-FTC) featured a higher concentration of volatile compounds compared to that in the control, particularly of all saturated and unsaturated aldehydes and esters, whereas the phenolic concentration was higher in VOO obtained from the traditional process (VOO-C).

  17. Effect of ion irradiation on the surface, structural and mechanical properties of brass

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Shahbaz; Bashir, Shazia, E-mail: shaziabashir@gcu.edu.pk; Ali, Nisar; Umm-i-Kalsoom,; Yousaf, Daniel; Faizan-ul-Haq,; Naeem, Athar; Ahmad, Riaz; Khlaeeq-ur-Rahman, M.

    2014-04-01

    Highlights: • Brass targets were exposed to carbon ions of energy 2 MeV. • The effect of ion dose has been investigated. • The surface morphology is investigated by SEM analysis. • XRD analysis is performed to reveal structural modification. • Mechanical properties were investigated by tensile testing and microhardness testing. - Abstract: Modifications to the surface, structural and mechanical properties of brass after ion irradiation have been investigated. Brass targets were bombarded by carbon ions of 2 MeV energy from a Pelletron linear accelerator for various fluences ranging from 56 × 10{sup 12} to 26 × 10{sup 13} ions/cm{sup 2}. A scanning electron microscope and X-ray diffractometer were utilized to analyze the surface morphology and crystallographic structure respectively. To explore the mechanical properties e.g., yield stress, ultimate tensile strength and microhardness of irradiated brass, an universal tensile testing machine and Vickers microhardness tester were used. Scanning electron microscopy results revealed an irregular and randomly distributed sputter morphology for a lower ion fluence. With increasing ion fluence, the incoherently shaped structures were transformed into dendritic structures. Nano/micro sized craters and voids, along with the appearance of pits, were observed at the maximum ion fluence. From X-ray diffraction results, no new phases were observed to be formed in the brass upon irradiation. However, a change in the peak intensity and higher and lower angle shifting were observed, which represents the generation of ion-induced defects and stresses. Analyses confirmed modifications in the mechanical properties of irradiated brass. The yield stress, ultimate tensile strength and hardness initially decreased and then increased with increasing ion fluence. The changes in the mechanical properties of irradiated brass are well correlated with surface and crystallographic modifications and are attributed to the generation

  18. Pseudomonas aeruginosa ceftolozane-tazobactam resistance development requires multiple mutations leading to overexpression and structural modification of AmpC.

    Science.gov (United States)

    Cabot, Gabriel; Bruchmann, Sebastian; Mulet, Xavier; Zamorano, Laura; Moyà, Bartolomé; Juan, Carlos; Haussler, Susanne; Oliver, Antonio

    2014-06-01

    occur efficiently only in a P. aeruginosa mutator background, in which multiple mutations lead to overexpression and structural modifications of AmpC. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

  19. Effect of surface topological structure and chemical modification of flame sprayed aluminum coatings on the colonization of Cylindrotheca closterium on their surfaces

    Science.gov (United States)

    Chen, Xiuyong; He, Xiaoyan; Suo, Xinkun; Huang, Jing; Gong, Yongfeng; Liu, Yi; Li, Hua

    2016-12-01

    Biofouling is one of the major problems for the coatings used for protecting marine infrastructures during their long-term services. Regulation in surface structure and local chemistry is usually the key for adjusting antifouling performances of the coatings. In this study, flame sprayed multi-layered aluminum coatings with micropatterned surfaces were constructed and the effects of their surface structure and chemistry on the settlement of typical marine diatoms were investigated. Micropatterned topographical morphology of the coatings was constructed by employing steel mesh as a shielding plate during the coating deposition. A silicone elastomer layer for sealing and interconnection was further brush-coated on the micropatterned coatings. Additional surface modification was made using zwitterionic molecules via DOPA linkage. The surface-modified coatings resist effectively colonization of Cylindrotheca closterium. This is explained by the quantitative examination of a simplified conditioning layer that deteriorated adsorption of bovine calf serum proteins on the zwitterionic molecule-treated samples is revealed. The colonization behaviors of the marine diatoms are markedly influenced by the micropatterned topographical morphology. Either the surface micropatterning or the surface modification by zwitterionic molecules enhances antimicrobial ability of the coatings. However, the combined micropatterned structure and zwitterionic modification do not show synergistic effect. The results give insight into anti-corrosion/fouling applications of the modified aluminum coatings in the marine environment.

  20. Asparagus cochinchinensis Extract Alleviates Metal Ion-Induced Gut Injury in Drosophila: An In Silico Analysis of Potential Active Constituents

    Directory of Open Access Journals (Sweden)

    Weiyu Zhang

    2016-01-01

    Full Text Available Metal ions and sulfate are components of atmospheric pollutants that have diverse ways of entering the human body. We used Drosophila as a model to investigate the effect of Asparagus cochinchinensis (A. cochinchinensis extracts on the gut and characterized gut homeostasis following the ingestion of metal ions (copper, zinc, and aluminum. In this study, we found that the aqueous A. cochinchinensis extract increased the survival rate, decreased epithelial cell death, and attenuated metal ion-induced gut morphological changes in flies following chronic exposure to metal ions. In addition, we screened out, by network pharmacology, six natural products (NPs that could serve as putative active components of A. cochinchinensis that prevented gut injury. Altogether, the results of our study provide evidence that A. cochinchinensis might be an effective phytomedicine for the treatment of metal ion-induced gut injury.

  1. Beam Energy Scaling of Ion-Induced Electron Yield from K+ Ions Impact on Stainless Steel Surfaces

    CERN Document Server

    Kireeff-Covo, Michel; Barnard, John J; Bieniosek, Frank; Celata, C M; Cohen, Ronald; Friedman, Alex; Grote, D P; Kwan, Joe W; Lund, Steven M; Molvik, Arthur; Seidl, Peter; Vay, Jean-Luc; Vujic, Jasmina L; Westenskow, Glen

    2005-01-01

    The cost of accelerators for heavy-ion inertial fusion energy (HIF) can be reduced by using the smallest possible clearance between the beam and the wall from the beamline. This increases beam loss to the walls, generating ion-induced electrons that could be trapped by beam space charge potential into an "electron cloud," which can cause degradation or loss of the ion beam. In order to understand the physical mechanism of production of ion-induced electrons we have measured impact of K+ ions with energies up to 400 KeV on stainless steel surfaces near grazing incidence, using the ion source test stand (STS-500) at LLNL. The electron yield will be discussed and compared with experimental measurements from 1 MeV K+ ions in the High-Current Experiment at LBNL.*

  2. Electronic excitation induced modifications in elongated iron nanoparticle encapsulated multiwalled carbon nanotubes under ion irradiation

    Science.gov (United States)

    Saikiran, V.; Bazylewski, P.; Sameera, I.; Bhatia, Ravi; Pathak, A. P.; Prasad, V.; Chang, G. S.

    2018-05-01

    Multi-wall carbon nanotubes (MWCNT) filled with Fe nanorods were shown to have contracted and deformed under heavy ion irradiation. In this study, 120 MeV Ag and 80 MeV Ni ion irradiation was performed to study the deformation and defects induced in iron filled MWCNT under heavy ion irradiation. The structural modifications induced due to electronic excitation by ion irradiation were investigated employing high-resolution transmission electron microscopy, micro-Raman scattering experiments, and synchrotron-based X-ray absorption and emission spectroscopy. We understand that the ion irradiation causes modifications in the Fe nanorods which result in compressions and expansions of the nanotubes, and in turn leads to the buckling of MWCNT. The G band of the Raman spectra shifts slightly towards higher wavenumber and the shoulder G‧ band enhances with the increase of ion irradiation fluence, where the buckling wavelength depends on the radius 'r' of the nanotubes as exp[(r)0.5]. The intensity ratio of the D to G Raman modes initially decreases at the lowest fluence, and then it increases with the increase in ion fluence. The electron diffraction pattern and the high resolution images clearly show the presence of ion induced defects on the walls of the tube and encapsulated iron nanorods.

  3. Structural systematics of rare earth complexes. III. Structural characterization of lanthanoid (III) picrate hydrates: gadolinium picrate dodecahydrate - an x-ray-induced phase modifications? - and some general aspects of structural chemistry of lanthanoid picrates

    International Nuclear Information System (INIS)

    Harrowfield, J.M.; Weimin, Lu; Brian, W.S.; White, A.H.

    1994-01-01

    In the course of the previous studies (Parts I and II), an unusual result was observed in the case of the structure determination of hydrated gadolinium(III) picrate. Midway through data collection, the monoclinic P2 1 /c phase modification (X-ray-induced?) to a similar cell more nearly resembling that of the La→Pr structure type recorded previously, with no loss of crystal integrity, and with useful data sets being obtained on both forms. Redetermination of the structure with a fresh sample yielded no reproduction of the anomaly. These results are recorded and discussed, together with an overview of the consequences of the data of Parts I-III in relation to those of other literature in the field. 13 refs., 4 tabs., 1 fig

  4. Nanodosimetric Simulation of Direct Ion-Induced DNA Damage Using Different Chromatin Geometry Models.

    Science.gov (United States)

    Henthorn, N T; Warmenhoven, J W; Sotiropoulos, M; Mackay, R I; Kirkby, K J; Merchant, M J

    2017-12-01

    Monte Carlo based simulation has proven useful in investigating the effect of proton-induced DNA damage and the processes through which this damage occurs. Clustering of ionizations within a small volume can be related to DNA damage through the principles of nanodosimetry. For simulation, it is standard to construct a small volume of water and determine spatial clusters. More recently, realistic DNA geometries have been used, tracking energy depositions within DNA backbone volumes. Traditionally a chromatin fiber is built within the simulation and identically replicated throughout a cell nucleus, representing the cell in interphase. However, the in vivo geometry of the chromatin fiber is still unknown within the literature, with many proposed models. In this work, the Geant4-DNA toolkit was used to build three chromatin models: the solenoid, zig-zag and cross-linked geometries. All fibers were built to the same chromatin density of 4.2 nucleosomes/11 nm. The fibers were then irradiated with protons (LET 5-80 keV/μm) or alpha particles (LET 63-226 keV/μm). Nanodosimetric parameters were scored for each fiber after each LET and used as a comparator among the models. Statistically significant differences were observed in the double-strand break backbone size distributions among the models, although nonsignificant differences were noted among the nanodosimetric parameters. From the data presented in this article, we conclude that selection of the solenoid, zig-zag or cross-linked chromatin model does not significantly affect the calculated nanodosimetric parameters. This allows for a simulation-based cell model to make use of any of these chromatin models for the scoring of direct ion-induced DNA damage.

  5. H-isotope retention and thermal/ion-induced release in boronized films

    International Nuclear Information System (INIS)

    Walsh, D.S.; Doyle, B.L.; Wampler, W.R.; Hays, A.K.

    1990-01-01

    Over the past decade, it has been clearly demonstrated that the composition of the very near surface (∼100nm) of plasma-interactive components plays a determinant role in most processes which occur in the plasma-edge of Tokamaks. Two very successful techniques to effect control of the plasma-wall interaction are (1) in-situ deposition of amorphous carbon or boron-carbon films and (2) the use of He/C conditioning discharges or He glow discharge cleaning to modify the near surface of bulk graphite components. We have deposited boronized layers into Si using plasma-assisted CVD and sputter deposition. The PCVD deposition conditions were as close as possible to those used in TFTR, and some films deposited in TFTR have also been studied. Using these two deposition techniques, B x CH y films have been produced with x varying from 1/2 -- 4, and y from ∼1 (sputtered) to ∼3 (PCVD). Most films also contained significant amounts of 0. Thermal and ion-induced release of H-isotopes from BC films is qualitatively similar to that measured for graphite. Implanted H saturates in these films at a H/host atom ratio of 0.7 which is considerably higher than that of graphite(∼0.4). As-deposited PCVD films are already saturated with H, while sputtered films are not. Sputtered BC films therefore possess an inherent H-pumping capability which could prove to be extremely beneficial to TFTR. 16 refs., 5 figs., 1 tab

  6. Electronic structure modification and Fermi level shifting in niobium-doped anatase titanium dioxide thin films: a comparative study of NEXAFS, work function and stiffening of phonons.

    Science.gov (United States)

    Gautam, Subodh K; Das, Arkaprava; Ojha, S; Shukla, D K; Phase, D M; Singh, Fouran

    2016-02-07

    The electronic structure and tuning of work function (WF) by electronic excitations (EEs) induced by swift heavy ions (SHIs) in anatase niobium-doped titanium dioxide (NTO) thin films is reported. The densities of EEs were varied using 80 MeV O, 130 MeV Ni and 120 MeV Ag ions for irradiation. The EE-induced modifications in electronic structure were studied by O K-edge and Ti L3,2 edge absorption spectra using near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The reduction of hybridized O 2p and Ti 3d unoccupied states in the conduction band with a decrease in energy of the crystal field strength of ∼ 480 meV and the correlated effect on the decrease in the WF value of ∼ 520 meV upon increasing the total energy deposition in the lattice are evident from the study of NEXAFS and scanning Kelvin probe microscopy (SKPM), respectively. The observed stiffening in the low frequency Raman mode (LFRM) of ∼ 9 cm(-1) further validates the electronic structure modification under the influence of EE-induced strain in TiO6 octahedra. The reduction of hybridized valence states, stiffening behavior of LFRM and decrease in WF by nano-crystallization followed by amorphization and defects in NTO lattice are explained in terms of continuous, discontinuous amorphous ion tracks containing intestinally created defects and non-stoichiometry in the lattice. These studies are very appropriate for better insights of electronic structure modification during phase transformation and controlled Fermi level shifting, which plays a crucial role in controlling the charge carrier injection efficiency in opto-electronic applications and also provides a deeper understanding of the involved physical processes.

  7. Full jet evolution in quark-gluon plasma and nuclear modification of jet structure in Pb+Pb collisions at 2.76A TeV

    Science.gov (United States)

    Chang, Ning-Bo; Qin, Guang-You

    2017-08-01

    We study the evolution of full jet shower in quark-gluon plasma via solving a set of coupled differential transport equations for the three-dimensional momentum distributions of quarks and gluons contained in the full jets. The evolution equations include all partonic splitting processes as well as the collisional energy loss and transverse momentum broadening for both the leading and radiated partons of the full jets. Combining with realistic hydrodynamic simulation for the space-time evolution of the fireball created in Pb+Pb collisions at 2.76A TeV, we calculate the nuclear modification of single inclusive full jet spectra, the momentum imbalance of photon-jet and dijet pairs, and jet shape function (at partonic level). The roles of various jet-medium interaction mechanisms on the modification of full jet energy and internal structure are studied.

  8. Tyrosine modifications in aging.

    Science.gov (United States)

    Feeney, Maria B; Schöneich, Christian

    2012-12-01

    The understanding of physiological and pathological processes involving protein oxidation, particularly under conditions of aging and oxidative stress, can be aided by proteomic identification of proteins that accumulate oxidative post-translational modifications only if these detected modifications are connected to functional consequences. The modification of tyrosine (Tyr) residues can elicit significant changes in protein structure and function, which, in some cases, may contribute to biological aging and age-related pathologies, such as atherosclerosis, neurodegeneration, and cataracts. Studies characterizing proteins in which Tyr has been modified to 3-nitrotyrosine, 3,4-dihydroxyphenylalanine, 3,3'-dityrosine and other cross-links, or 3-chlorotyrosine are reviewed, with an emphasis on structural and functional consequences. Distinguishing between inconsequential modifications and functionally significant ones requires careful biochemical and biophysical analysis of target proteins, as well as innovative methods for isolating the effects of the multiple modifications that often occur under oxidizing conditions. The labor-intensive task of isolating and characterizing individual modified proteins must continue, especially given the expanding list of known modifications. Emerging approaches, such as genetic and metabolic incorporation of unnatural amino acids, hold promise for additional focused studies of this kind.

  9. A hypertension-associated mitochondrial DNA mutation introduces an m1G37 modification into tRNAMet, altering its structure and function.

    Science.gov (United States)

    Zhou, Mi; Xue, Ling; Chen, Yaru; Li, Haiying; He, Qiufen; Wang, Bibin; Meng, Feilong; Wang, Meng; Guan, Min-Xin

    2018-01-26

    Defective nucleotide modifications of mitochondrial tRNAs have been associated with several human diseases, but their pathophysiology remains poorly understood. In this report, we investigated the pathogenic molecular mechanism underlying a hypertension-associated 4435A→G mutation in mitochondrial tRNA Met The m.4435A→G mutation affected a highly conserved adenosine at position 37, 3' adjacent to the tRNA's anticodon, which is important for the fidelity of codon recognition and stabilization. We hypothesized that the m.4435A→G mutation introduced an m 1 G37 modification of tRNA Met , altering its structure and function. Primer extension and methylation activity assays indeed confirmed that the m.4435A→G mutation created a tRNA methyltransferase 5 (TRMT5)-catalyzed m 1 G37 modification of tRNA Met We found that this mutation altered the tRNA Met structure, indicated by an increased melting temperature and electrophoretic mobility of the mutated tRNA compared with the wildtype molecule. We demonstrated that cybrid cell lines carrying the m.4435A→G mutation exhibited significantly decreased efficiency in aminoacylation and steady-state levels of tRNA Met , as compared with those of control cybrids. The aberrant tRNA Met metabolism resulted in variable decreases in mitochondrial DNA (mtDNA)-encoded polypeptides in the mutant cybrids. Furthermore, we found that the m.4435A→G mutation caused respiratory deficiency, markedly diminished mitochondrial ATP levels and membrane potential, and increased the production of reactive oxygen species in mutant cybrids. These results demonstrated that an aberrant m 1 G37 modification of mitochondrial tRNA Met affected the structure and function of its tRNA and consequently altered mitochondrial function. Our findings provide critical insights into the pathophysiology of maternally inherited hypertension, which is manifested by the deficient tRNA nucleotide modification. © 2018 by The American Society for Biochemistry and

  10. Error analysis and prevention of cosmic ion-induced soft errors in static CMOS RAMS

    International Nuclear Information System (INIS)

    Diehl, S.E.; Ochoa, A. Jr.; Dressendorfer, P.V.; Koga, R.; Kolasinski, W.A.

    1982-06-01

    Cosmic ray interactions with memory cells are known to cause temporary, random, bit errors in some designs. The sensitivity of polysilicon gate CMOS static RAM designs to logic upset by impinging ions has been studied using computer simulations and experimental heavy ion bombardment. Results of the simulations are confirmed by experimental upset cross-section data. Analytical models have been extended to determine and evaluate design modifications which reduce memory cell sensitivity to cosmic ions. A simple design modification, the addition of decoupling resistance in the feedback path, is shown to produce static RAMs immune to cosmic ray-induced bit errors

  11. Discriminating Self and Non-Self by RNA: Roles for RNA Structure, Misfolding, and Modification in Regulating the Innate Immune Sensor PKR

    Science.gov (United States)

    2017-01-01

    CONSPECTUS Pathogens are recognized by the innate immune system in part via their unique and complex RNA signatures. A key sensor in human innate immunity is the RNA-activated protein kinase PKR, which has two double-stranded RNA (dsRNA) binding motifs (dsRBMs) at its N-terminus. Early studies described PKR as being activated potently by long stretches of perfect dsRNA, a signature typical of viruses. More recently, we and others have found that PKR is also activated by RNAs having structural defects such as bulges and internal loops. This article describes advances in our understanding of the ability of PKR to detect diverse foreign RNAs and how that recognition plays significant roles in discriminating self from non-self. The experiments discussed employ a wide range of techniques including activation assays, native polyacrylamide gel electrophoresis (PAGE), protein footprinting, and small angle X-ray scattering (SAXS). We discuss how misfolding and dimerization of RNA lead to activation of PKR. We also present recent findings on the activation of PKR by varied bacterial functional RNAs including ribozymes and riboswitches, which are among the few structured RNAs known to interact with PKR in a site-specific manner. Molecular models for how these structured RNAs activate PKR are provided. Studies by SAXS revealed that PKR straightens bent RNAs. Most external and internal RNA cellular modifications introduced in vitro and found naturally, such as the m7G cap and m6A group, abrogate activation of PKR, but other modifications, such as 5’-ppp and 2’-fluoro groups, are immunostimulatory and potential anticancer agents. Genome-wide studies of RNA folding in vitro and in vivo have provided fresh insights into general differences in RNA structure amongst bacteria, viruses, and human. These studies suggest that in vivo, cellular human RNAs are less folded than once thought, unwound by helicases, destabilized by m6A modifications, and often bound up with proteins

  12. Understanding the conformational impact of chemical modifications on monoclonal antibodies with diverse sequence variation using hydrogen/deuterium exchange mass spectrometry and structural modeling.

    Science.gov (United States)

    Zhang, Aming; Hu, Ping; MacGregor, Paul; Xue, Yu; Fan, Haihong; Suchecki, Peter; Olszewski, Leonard; Liu, Aston

    2014-04-01

    Chemical modifications can potentially induce conformational changes near the modification site and thereby impact the safety and efficacy of protein therapeutics. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) has emerged as a powerful analytical technique with high spatial resolution and sensitivity in detecting such local conformational changes. In this study, we utilized HDX-MS combined with structural modeling to examine the conformational impact on monoclonal antibodies (mAbs) caused by common chemical modifications including methionine (Met) oxidation, aspartic acid (Asp) isomerization, and asparagine (Asn) deamidation. Four mAbs with diverse sequences and glycosylation states were selected. The data suggested that the impact of Met oxidation was highly dependent on its location and glycosylation state. For mAbs with normal glycosylation in the Fc region, oxidation of the two conserved Met252 and Met428 (Kabat numbering) disrupted the interface interactions between the CH2 and CH3 domains, thus leading to a significant decrease in CH2 domain thermal stability as well as a slight increase in aggregation propensity. In contrast, Met oxidation in the variable region and CH3 domain had no detectable impact on mAb conformation. For aglycosylated mAb, Met oxidation could cause a more global conformational change to the whole CH2 domain, coincident with the larger decrease in thermal stability and significant increase in aggregation rate. Unlike Met oxidation, Asn deamidation and Asp isomerization mostly had very limited effects on mAb conformation, with the exception of succiminide intermediate formation which induced a measurable local conformational change to be more solvent protected. Structural modeling suggested that the succinimide intermediate was stabilized by adjacent aromatic amino acids through ring-ring stacking interactions.

  13. Hydroimidazolone modification of the conserved Arg12 in small heat shock proteins: studies on the structure and chaperone function using mutant mimics.

    Directory of Open Access Journals (Sweden)

    Ram H Nagaraj

    Full Text Available Methylglyoxal (MGO is an α-dicarbonyl compound present ubiquitously in the human body. MGO reacts with arginine residues in proteins and forms adducts such as hydroimidazolone and argpyrimidine in vivo. Previously, we showed that MGO-mediated modification of αA-crystallin increased its chaperone function. We identified MGO-modified arginine residues in αA-crystallin and found that replacing such arginine residues with alanine residues mimicked the effects of MGO on the chaperone function. Arginine 12 (R12 is a conserved amino acid residue in Hsp27 as well as αA- and αB-crystallin. When treated with MGO at or near physiological concentrations (2-10 µM, R12 was modified to hydroimidazolone in all three small heat shock proteins. In this study, we determined the effect of arginine substitution with alanine at position 12 (R12A to mimic MGO modification on the structure and chaperone function of these proteins. Among the three proteins, the R12A mutation improved the chaperone function of only αA-crystallin. This enhancement in the chaperone function was accompanied by subtle changes in the tertiary structure, which increased the thermodynamic stability of αA-crystallin. This mutation induced the exposure of additional client protein binding sites on αA-crystallin. Altogether, our data suggest that MGO-modification of the conserved R12 in αA-crystallin to hydroimidazolone may play an important role in reducing protein aggregation in the lens during aging and cataract formation.

  14. Delineation of the structural and functional role of Arg111 in GSTU4-4 from Glycine max by chemical modification and site-directed mutagenesis.

    Science.gov (United States)

    Labrou, Nikolaos E; Muharram, Magdy Mohamed; Abdelkader, Maged Saad

    2016-10-01

    The structural and functional role of Arg111 in GSTU4-4 from Glycine max (GmGSTU4-4) was studied by chemical modification followed by site-directed mutagenesis. The arginine-specific reagent 2,3-butanedione (BTD) inactivates the enzyme in borate buffer at pH8.0, with pseudo-first-order saturation kinetics. The rate of inactivation exhibited a non-linear dependence on the concentration of BTD which can be described by reversible binding of reagent to the enzyme (KD 81.2±9.2mM) prior to the irreversible reaction, with maximum rate constants of 0.18±0.01min(-1). Protection from inactivation was afforded by substrate analogues demonstrating the specificity of the reaction. Structural analysis suggested that the modified residue is Arg111, which was confirmed by protein chemistry experiments. Site-directed mutagenesis was used in dissecting the role of Arg111 in substrate binding, specificity and catalytic mechanism. The mutant Arg111Ala enzyme exhibited unchanged Km value for GSH but showed reduced affinity for the xenobiotic substrates, higher kcat and specific activities towards aromatic substrates and lower specific activities towards aliphatic substrates. The biological significance of the specific modification of Arg111 by dicarbonyl compounds and the role of Arg111 as a target for engineering xenobiotic substrate specificity were discussed. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Matrix effects in ion-induced emission as observed in Ne collisions with Cu-Mg and Cu-Al alloys

    Science.gov (United States)

    Ferrante, J.; Pepper, S. V.

    1983-01-01

    Ion induced Auger electron emission is used to study the surfaces of Al, Mg, Cu - 10 at. % Al, Cu - 19.6 at. % Al, and Cu - 7.4 at. % Mg. A neon (Ne) ion beam whose energy is varied from 0.5 to 3 keV is directed at the surface. Excitation of the lighter Ne occurs by the promotion mechanism of Barat and Lichten in asymmetric collisions with Al or Mg atoms. Two principal Auger peaks are observed in the Ne spectrum: one at 22 eV and one at 25 eV. Strong matrix effects are observed in the alloys as a function of energy in which the population of the second peak is greatly enhanced relative to the first over the pure materials. For the pure material over this energy range this ratio is 1.0. For the alloys it can rise to the electronic structure of alloys and to other surface tools such as secondary ion mass spectroscopy.

  16. Aerosol charging state at an urban site: new analytical approach and implications for ion-induced nucleation

    Directory of Open Access Journals (Sweden)

    S. Gagné

    2012-05-01

    Full Text Available The charging state of aerosol populations was determined using an Ion-DMPS in Helsinki, Finland between December 2008 and February 2010. We extrapolated the charging state and calculated the ion-induced nucleation fraction to be around 1.3 % ± 0.4 % at 2 nm and 1.3 % ± 0.5 % at 1.5 nm, on average. We present a new method to retrieve the average charging state for a new particle formation event, at a given size and polarity. We improve the uncertainty assessment and fitting technique used previously with an Ion-DMPS. We also use a new theoretical framework that allows for different concentrations of small ions for different polarities (polarity asymmetry. We extrapolate the ion-induced fraction using polarity symmetry and asymmetry. Finally, a method to calculate the growth rates from the behaviour of the charging state as a function of the particle diameter using polarity symmetry and asymmetry is presented and used on a selection of new particle formation events.

  17. Correlation between the structure modification and conductivity of 3 MeV Si ion-irradiated polyimide

    International Nuclear Information System (INIS)

    Sun Youmei; Zhu Zhiyong; Li Changlin

    2002-01-01

    The surface modification of the polyimide (PI/Kapton) films was carried out by 3 MeV Si + implantation to fluences ranging from 1x10 12 to 1.25x10 15 ions/cm 2 . Fourier transform infrared (FTIR), Raman and ultraviolet/visible (UV/Vis) spectroscopes were employed to investigate the chemical degradation of function groups in the irradiated layer. FTIR results show that the absorbance of typical function group decreases exponentially as a function of fluence. The damage cross-section of typical bonds of PI was evaluated from the FTIR spectra. Raman analysis shows the absorbed dose for destruction of all function groups is above 218 MGy. The red shifting of the absorption edge from UV to visible reveals the band gap closing which results from increase of the cluster size. The production efficiency of the chromophores was discussed according to UV/Vis analysis. Irradiation dramatically enhances the electrical conductivity and the sheet resistivity in our experiment descends nearly 10 orders of magnitude compared with its intrinsic value

  18. The formation and modification of chromatin-like structure of human parvovirus B19 regulate viral genome replication and RNA processing.

    Science.gov (United States)

    Xu, Huanzhou; Hao, Sujuan; Zhang, Junmei; Chen, Zhen; Wang, Hanzhong; Guan, Wuxiang

    2017-03-15

    B19 virus (B19V) is a single stranded virus in the genus of Erythroparvovirus in the family of Parvoviridae. One of the limiting steps of B19V infection is the replication of viral genome which affected the alternative processing of its RNA. Minute virus of mice (MVM) and adeno-associated virus (AAV) has been reported to form chromatin-like structure within hours after infection of cells. However, the role of chromatin-like structure is unclear. In the present study, we found that B19V formed chromatin-like structure after 12h when B19V infectious clone was co-transfected with pHelper plasmid to HEK293T cells. Interestingly, the inhibitor of DNA methyl-transferase (5-Aza-2'-deoxycytidine, DAC) inhibited not only the formation of chromatin-like structure, but also the replication of the viral genomic DNA. More importantly, the splicing of the second intron at splice acceptor sites (A2-1, and A2-2) were reduced and polyadenylation at (pA)p increased when transfected HEK293T cells were treated with DAC. Our results showed that the formation and modification of chromatin-like structure are a new layer to regulate B19V gene expression and RNA processing. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. The structure and function of ribonuclease T1. XXI. Modification of histidine residues in ribonuclease T1 with iodoacetamide.

    Science.gov (United States)

    Takahashi, K

    1976-12-01

    1. When ribonuclease T1 [EC 3.1.4.8] (0.125% solution) was treated with a 760-fold molar excess of iodoacetamide at pH 8.0 and 37 degrees, about 90% of the original activity was lost in 24 hr. The half-life of the activity was about 8 hr. The binding ability for 3'-GMP was lost simultaneously. Changes were detected only in histidine and the amino-terminal alanine residues upon amino acid analyses of the inactivated protein and its chymotryptic peptides. The inactivation occurred almost in parallel with the loss of two histidine residues in the enzyme. The pH dependences of the rate of inactivation and that of loss of histidine residues were similar and indicated the implication of a histidine residue or residues with pKa 7.5 to 8 in this reaction. 3'-GMP and guanosine showed some protective effect against loss of activity and of histidine residues. The reactivity of histidine residues was also reduced by prior modification of glutamic acid-58 with iodoacetate, of lysine-41 with maleic or cis-aconitic anhydride or 2,4,6-trinitrobenzenesulfonate or of arginine-77 with ninhydrin. 2. Analyses of the chymotryptic peptides from oxidized samples of the iodoacetamide-inactivated enzyme showed that histidine-92 and histidine-40 reacted with iodoacetamide most rapidly and at similar rates, whereas histidine-27 was least reactive. Alkylation of histidine-92 was markedly slowed down when the Glu58-carboxymethylated enzyme was treated with iodoacetamide. On the other hand, alkylation of histidine-40 was slowed down most in the presence of 3'-GMP. These results suggest that histidine-92 and histidine-40 are involved in the catalytic action, probably forming part of the catalytic site and part of the binding site, respectively, and that histidine-27 is partially buried in the enzyme molecule or interacts strongly with some other residue, thus becoming relatively unreactive.

  20. Structural characterization of the high-temperature modification of the Cu{sub 2}ZnGeTe{sub 4} quaternary semiconductor compound

    Energy Technology Data Exchange (ETDEWEB)

    Nieves, L.; Marcano, G.; Power, C.; Rincon, C. [Centro de Estudios de Semiconductores, Departamento de Fisica, Facultad de Ciencias, Universidad de Los Andes, Merida, 5101 (Venezuela, Bolivarian Republic of); Delgado, G.E. [Laboratorio de Cristalografia, Departamento de Quimica, Facultad de Ciencias, Universidad de Los Andes, Merida, 5101 (Venezuela, Bolivarian Republic of); Lopez-Rivera, S.A. [Grupo de Fisica Aplicada, Departamento de Fisica, Facultad de Ciencias, Universidad de Los Andes, Merida, 5101 (Venezuela, Bolivarian Republic of)

    2016-06-15

    A combined study of the X-ray powder diffraction, differential thermal analysis, optical absorption, and Raman spectroscopy of the high-temperature modification of Cu{sub 2}ZnGeTe{sub 4} quaternary semiconductor, obtained by fast quenching from 820 K to ice water temperature, has been done. It has been found that this phase crystallizes in a tetragonal kesterite-type structure. From the analysis of the absorption coefficient spectra, the band gap energy of this material at room temperature has been found to be 1.49 eV. An optical transition from defect acceptor states to the conduction band is also observed below the fundamental absorption edge. Three strongest Raman lines observed at 116, 119, and 139 cm{sup -1} have been assigned to the A-symmetry modes. Also, lines at 81, 89, 97, and 263 cm{sup -1} tentatively ascribed as B or E-symmetry modes have been detected from the spectrum. The presence in this high-temperature modification of ZnTe and Cu{sub 2}GeTe{sub 3} secondary phases has been detected by both XRD and Raman spectroscopy. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Temperature and Magnetic Field Driven Modifications in the I-V Features of Gold-DNA-Gold Structure

    Directory of Open Access Journals (Sweden)

    Nadia Mahmoudi Khatir

    2014-10-01

    Full Text Available The fabrication of Metal-DNA-Metal (MDM structure-based high sensitivity sensors from DNA micro-and nanoarray strands is a key issue in their development. The tunable semiconducting response of DNA in the presence of external electromagnetic and thermal fields is a gift for molecular electronics. The impact of temperatures (25–55 °C and magnetic fields (0–1200 mT on the current-voltage (I-V features of Au-DNA-Au (GDG structures with an optimum gap of 10 μm is reported. The I-V characteristics acquired in the presence and absence of magnetic fields demonstrated the semiconducting diode nature of DNA in GDG structures with high temperature sensitivity. The saturation current in the absence of magnetic field was found to increase sharply with the increase of temperature up to 45 °C and decrease rapidly thereafter. This increase was attributed to the temperature-assisted conversion of double bonds into single bond in DNA structures. Furthermore, the potential barrier height and Richardson constant for all the structures increased steadily with the increase of external magnetic field irrespective of temperature variations. Our observation on magnetic field and temperature sensitivity of I-V response in GDG sandwiches may contribute towards the development of DNA-based magnetic sensors.

  2. Structure and Properties of Polypropylene Fibres Modiffed with Photoluminescent Pigment as a Tool for the Protection of Original Products

    Directory of Open Access Journals (Sweden)

    Zita Tomčikova

    2017-12-01

    Full Text Available A special photoluminescent inorganic pigment was used as a tool to protect polypropylene (PP fibre originality. The effect of pigment content and uniaxial deformation on the supermolecular structure and basic mechanical properties of PP fibres modified with the above-mentioned pigment were investigated, together with its colour performance under a UV lamp. Supermolecular structure parameters, such as birefringence, sound velocity in fibres, crystallinity and the crystallinity index of undrawn and drawn modified PP fibres prepared using a discontinuous technological process, were studied. Mechanical properties such as fi neness, Young’s modulus, tenacity at break and elongation at break of undrawn and drawn modified fibres were evaluated. The obtained experimental results of modified PP fibres were compared with the supermolecular structure and mechanical characteristics of standard unmodified PP fibres prepared under same technological conditions.

  3. Enhancement of cell growth on honeycomb-structured polylactide surface using atmospheric-pressure plasma jet modification

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Kuang-Yao; Chang, Chia-Hsing; Yang, Yi-Wei; Liao, Guo-Chun; Liu, Chih-Tung; Wu, Jong-Shinn, E-mail: chongsin@faculty.nctu.edu.tw

    2017-02-01

    Graphical abstract: Atmospheric-pressure plasma enhances cell growth on two different pore sizes of honeycomb pattern on polylactide surface. - Highlights: • Different pore sizes of honeycomb pattern on PLA film are created. • The two-step plasma treatment provided the oxygen- and nitrogen-containing functional groups that had a major impact on cell cultivation. • The plasma treatment had a significant effect for cell proliferation. • The surface structures are the main influence on cell cultivation, while plasma treatment can indeed improve the growth environment. - Abstract: In this paper, we compare the cell growth results of NIH-3T3 and Neuro-2A cells over 72 h on flat and honeycomb structured PLA films without and with a two-step atmospheric-pressure nitrogen-based plasma jet treatment. We developed a fabrication system used for forming of a uniform honeycomb structure on PLA surface, which can produce two different pore sizes, 3–4 μm and 7–8 μm, of honeycomb pattern. We applied a previously developed nitrogen-based atmospheric-pressure dielectric barrier discharge (DBD) jet system to treat the PLA film without and with honeycomb structure. NIH-3T3 and a much smaller Neuro-2A cells were cultivated on the films under various surface conditions. The results show that the two-step plasma treatment in combination with a honeycomb structure can enhance cell growth on PLA film, should the cell size be not too smaller than the pore size of honeycomb structure, e.g., NIH-3T3. Otherwise, cell growth would be better on flat PLA film, e.g., Neuro-2A.

  4. Structure and molecular motion in three modifications of a binary C23H48-C24H50 paraffin

    International Nuclear Information System (INIS)

    Craievich, A.F.; Denicolo, I.; Doucet, J.

    1983-01-01

    The temperature dependence of the intensities of the (00l) X-ray reflections from a binary paraffin (C 23 H 48 -25% C 24 H 50 ) was determined, in order to obtain structure parameters related to the molecular motion and intramolecular defects. The long lattice spacing was also determined as a function of the temperature. All of these results are compared with the temperature dependence of the ratio of the two short lattice parameters. The clear correlation of all of these experimental results provides a close characterization of the molecular structures and their changes at the several solid state phase transitions. (Author) [pt

  5. Modification of potato starch granule structure and morphology in planta by expression of starch binding domain fusion proteins

    NARCIS (Netherlands)

    Huang, X.

    2010-01-01

    Producing starches with altered composition, structure and novel physico-chemical properties in planta by manipulating the enzymes which are involved in starch metabolism or (over)expressing heterologous enzymes has huge advantages such as broadening the range of starch applications and reducing the

  6. Structural modifications of type C rare earth sesquioxyde Yb203 and Er203 in function of temperature

    International Nuclear Information System (INIS)

    Saiki, A.; Ishizawa, N.

    1988-03-01

    Monocrystal structure of Yb 2 0 3 and Er 2 0 3 is analyzed with a X-ray diffractometer from ambiant temperature to 1260 K and mean linear thermal dilatation coefficients of crystal network unit mesh are measured for both oxides. Relationship between oxygen atom pattern and oxygen-metal length and evolution with temperature are studied [fr

  7. Synthesis, Crystal Structure, and Topology-Symmetry Analysis of a New Modification of NaIn[IO3]4

    Science.gov (United States)

    Belokoneva, E. L.; Karamysheva, A. S.; Dimitrova, O. V.; Volkov, A. S.

    2018-01-01

    Crystals of new iodate NaIn[IO3]4 were prepared by the hydrothermal synthesis. The unit cell parameters are a = 7.2672(2) Å, b = 15.2572(6) Å, c = 15.0208(6) Å, β = 101.517(3)°, sp. gr. P21/ c. The formula was determined during the structure determination and refinement of a twinned crystal based on a set of reflections from the atomic planes of the major individual. The refinement with anisotropic displacement parameters was performed for both twin components to the final R factor of 0.050. The In and Na atoms are in octahedral coordination formed by oxygen atoms. The oxygen octahedra are arranged into columns by sharing edges, and the columns are connected by isolated umbrella-like [IO3]- groups to form layers. The new structure is most similar to the isoformular iodate NaIn[IO3]4, which crystallizes in the same sp. gr. P21/ c and is structurally similar, but has a twice smaller unit cell and is characterized by another direction of the monoclinic axis. The structural similarity and difference between the two phases were studied by topologysymmetry analysis. The formation of these phases is related to different combinations of identical one-dimensional infinite chains of octahedra.

  8. The roles of energetic displacement cascades in ion beam modifications of materials

    International Nuclear Information System (INIS)

    Averback, R.S.; Kim, S.J.; De la Rubia, T.D.

    1987-01-01

    The roles of energetic displacement cascades are ubiquitous in the fields of radiation damage and ion beam modifications of materials. These roles can be described on two time scales. For the first, which lasts ≅ 10/sup -11/ s, small cascade volumes are characterized by large supersaturations of point defects, structural disorder, and energy densities in excess of some tenths of eV's per atom. During this period, the system can be driven far from equilibrium with significant rearrangement of target atoms and the production of Frenkel pairs. Experimental studies of ion beam mixing in conjunction with molecular dynamics computer simulations, have contributed largely toward understanding these dynamic cascade processes. At later times, the microstructure of the material evolves as cascades begin to overlap, or at elevated temperatures, point defects migrate away from their nascent cascades. It is shown how the primary state of damage in cascades influences this microstructural development. Examples involving radiation-enhanced diffusion and ion-induced amorphization are discussed

  9. Salicylate-Induced Hearing Loss Trigger Structural Synaptic Modifications in the Ventral Cochlear Nucleus of Rats via Medial Olivocochlear (MOC) Feedback Circuit.

    Science.gov (United States)

    Fang, Lian; Fu, YaoYao; Zhang, Tian-Yu

    2016-06-01

    Lesion-induced cochlear damage can result in synaptic outgrowth in the ventral cochlear nucleus (VCN). Tinnitus may be associated with the synaptic outgrowth and hyperactivity in the VCN. However, it remains unclear how hearing loss triggers structural synaptic modifications in the VCN of rats subjected to salicylate-induced tinnitus. To address this issue, we evaluated tinnitus-like behavior in rats after salicylate treatment and compared the amplitude of the distortion product evoked otoacoustic emission (DPOAE) and auditory brainstem response (ABR) between control and treated rats. Moreover, we observed the changes in the synaptic ultrastructure and in the expression levels of growth-associated protein (GAP-43), brain-derived neurotrophic factor (BDNF), the microglial marker Iba-1 and glial fibrillary acidic protein (GFAP) in the VCN. After salicylate treatment (300 mg/kg/day for 4 and 8 days), analysis of the gap prepulse inhibition of the acoustic startle showed that the rats were experiencing tinnitus. The changes in the DPOAE and ABR amplitude indicated an improvement in cochlear sensitivity and a reduction in auditory input following salicylate treatment. The treated rats displayed more synaptic vesicles and longer postsynaptic density in the VCN than the control rats. We observed that the GAP-43 expression, predominantly from medial olivocochlear (MOC) neurons, was significantly up-regulated, and that BDNF- and Iba-1-immunoreactive cells were persistently decreased after salicylate administration. Furthermore, GFAP-immunoreactive astrocytes, which is associated with synaptic regrowth, was significantly increased in the treated groups. Our study revealed that reduced auditory nerve activity triggers synaptic outgrowth and hyperactivity in the VCN via a MOC neural feedback circuit. Structural synaptic modifications may be a reflexive process that compensates for the reduced auditory input after salicylate administration. However, massive increases in

  10. Effect of fluence and ambient environment on the surface and structural modification of femtosecond laser irradiated Ti

    International Nuclear Information System (INIS)

    Umm-i-Kalsoom; Ali, Nisar; Husinsky, Wolfgang; Nathala, Chandra S R; Bashir, Shazia; Shahid Rafique, M; Makarov, Sergey V; Begum, Narjis

    2016-01-01

    Under certain conditions, ultrafast pulsed laser interaction with matter leads to the formation of self-organized conical as well as periodic surface structures (commonly reffered to as, laser induced periodic surface structures, LIPSS). The purpose of the present investigations is to explore the effect of fsec laser fluence and ambient environments (Vacuum and O 2 ) on the formation of LIPSS and conical structures on the Ti surface. The surface morphology was investigated by scanning electron microscope (SEM). The ablation threshold with single and multiple (N = 100) shots and the existence of an incubation effect was demonstrated by SEM investigations for both the vacuum and the O 2 environment. The phase analysis and chemical composition of the exposed targets were performed by x-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS), respectively. SEM investigations reveal the formation of LIPSS (nano and micro). FFT d-spacing calculations illustrate the dependence of periodicity on the fluence and ambient environment. The periodicity of nano-scale LIPSS is higher in the case of irradiation under vacuum conditions as compared to O 2 . Furthermore, the O 2 environment reduces the ablation threshold. XRD data reveal that for the O 2 environment, new phases (oxides of Ti) are formed. EDS analysis exhibits that after irradiation under vacuum conditions, the percentage of impurity element (Al) is reduced. The irradiation in the O 2 environment results in 15% atomic diffusion of oxygen. (paper)

  11. Structure based modification of Bluetongue virus helicase protein VP6 to produce a viable VP6-truncated BTV

    Energy Technology Data Exchange (ETDEWEB)

    Matsuo, Eiko [Microbiology and Immunology, Division of Animal Science, Department of Bioresource Science, Graduate School of Agricultural Science, Kobe University, 1-1, Rokkodai, Nada-ku, Kobe-City 657-8501 (Japan); Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT (United Kingdom); Leon, Esther; Matthews, Steve J. [Division of Molecular Biosciences, Centre for Structural Biology, Imperial College London, South Kensington, London SW7 2AZ (United Kingdom); Roy, Polly, E-mail: polly.roy@lshtm.ac.uk [Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT (United Kingdom)

    2014-09-05

    Highlights: • NMR analysis on BTV VP6 reveals two large loop regions. • The loss of a loop (aa 34–130) does not affect the overall fold of the protein. • A region of VP6 (aa 34–92) is not required for BTV replication. • A region of VP6 (aa 93–130) plays an essential role in the virus replication. - Abstract: Bluetongue virus core protein VP6 is an ATP hydrolysis dependent RNA helicase. However, despite much study, the precise role of VP6 within the viral capsid and its structure remain unclear. To investigate the requirement of VP6 in BTV replication, we initiated a structural and biological study. Multinuclear nuclear magnetic resonance spectra were assigned on his-tagged full-length VP6 (329 amino acid residues) as well as several truncated VP6 variants. The analysis revealed a large structured domain with two large loop regions that exhibit significant conformational exchange. One of the loops (amino acid position 34–130) could be removed without affecting the overall fold of the protein. Moreover, using a BTV reverse genetics system, it was possible to demonstrate that the VP6-truncated BTV was viable in BHK cells in the absence of any helper VP6 protein, suggesting that a large portion of this loop region is not absolutely required for BTV replication.

  12. Effect of hydrothermal modification on the porous structure and thermal properties of carbon-silica adsorbents (carbosils)

    International Nuclear Information System (INIS)

    Skubiszewska-Zieba, J.; Charmas, B.; Leboda, R.; Staszczuk, P.; Kowalczyk, P.; Oleszczuk, P.

    2003-01-01

    Characterisation of porous structure and thermal properties of unmodified and hydrothermally modified (using H 2 O 2 , under high pressure conditions) carbon-silica adsorbents (carbosils) prepared by dichloromethane pyrolysis (under dynamic conditions) on the surface of narrow pore silica were discussed. The analysis was made based on the data of low-temperature nitrogen adsorption/desorption isotherms, transmission electron microscopy (TEM) and the results of differential thermal analysis. It was stated that both porous structure and thermal properties of tested samples are in correlation with the morphology and topography of the carbon deposit. This deposit forms globules and aggregates whose size and position on the inner and outer surface of silica depends on the time of its carbonisation. It was stated that hydrothermal treatment (HTT) of the carbosils changes both the porous structure and thermal properties of the tested samples. As a result of HTT of silica, decondensation and recondensation of orthosilic acid on large particles of silica takes place. Then a decrease in the specific surface area and increase in the radius of pores are observed. In the case of carbosils these changes are smaller and depend on the accessibility of the silica surface, which is connected with topography of carbon deposit

  13. Amines are likely to enhance neutral and ion-induced sulfuric acid-water nucleation in the atmosphere more effectively than ammonia

    Directory of Open Access Journals (Sweden)

    T. Kurtén

    2008-07-01

    Full Text Available We have studied the structure and formation thermodynamics of dimer clusters containing H2SO4 or HSO4 together with ammonia and seven different amines possibly present in the atmosphere, using the high-level ab initio methods RI-MP2 and RI-CC2. As expected from e.g. proton affinity data, the binding of all studied amine-H2SO4 complexes is significantly stronger than that of NH3•H2SO4, while most amine-HSO4 complexes are only somewhat more strongly bound than NH3•HSO4. Further calculations on larger cluster structures containing dimethylamine or ammonia together with two H2SO4 molecules or one H2SO4 molecule and one HSO4 ion demonstrate that amines, unlike ammonia, significantly assist the growth of not only neutral but also ionic clusters along the H2SO4 co-ordinate. A sensitivity analysis indicates that the difference in complexation free energies for amine- and ammonia-containing clusters is large enough to overcome the mass-balance effect caused by the fact that the concentration of amines in the atmosphere is probably 2 or 3 orders of magnitude lower than that of ammonia. This implies that amines might be more important than ammonia in enhancing neutral and especially ion-induced sulfuric acid-water nucleation in the atmosphere.

  14. The crystal structure of Giardia duodenalis 14-3-3 in the apo form: when protein post-translational modifications make the difference.

    Directory of Open Access Journals (Sweden)

    Annarita Fiorillo

    Full Text Available The 14-3-3s are a family of dimeric evolutionary conserved pSer/pThr binding proteins that play a key role in multiple biological processes by interacting with a plethora of client proteins. Giardia duodenalis is a flagellated protozoan that affects millions of people worldwide causing an acute and chronic diarrheal disease. The single giardial 14-3-3 isoform (g14-3-3, unique in the 14-3-3 family, needs the constitutive phosphorylation of Thr214 and the polyglycylation of its C-terminus to be fully functional in vivo. Alteration of the phosphorylation and polyglycylation status affects the parasite differentiation into the cyst stage. To further investigate the role of these post-translational modifications, the crystal structure of the g14-3-3 was solved in the unmodified apo form. Oligomers of g14-3-3 were observed due to domain swapping events at the protein C-terminus. The formation of filaments was supported by TEM. Mutational analysis, in combination with native PAGE and chemical cross-linking, proved that polyglycylation prevents oligomerization. In silico phosphorylation and molecular dynamics simulations supported a structural role for the phosphorylation of Thr214 in promoting target binding. Our findings highlight unique structural features of g14-3-3 opening novel perspectives on the evolutionary history of this protein family and envisaging the possibility to develop anti-giardial drugs targeting g14-3-3.

  15. High fluence swift heavy ion structure modification of the SiO{sub 2}/Si interface and gate insulator in 65 nm MOSFETs

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Yao [Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Key Lab of Microelectronics Sichuan Province, Sichuan University, Chengdu, Sichuan 610064 (China); College of Physical Science and Technology, Sichuan University, Chengdu, Sichuan 610064 (China); Gao, Bo, E-mail: gaobo@scu.edu.cn [Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Key Lab of Microelectronics Sichuan Province, Sichuan University, Chengdu, Sichuan 610064 (China); College of Physical Science and Technology, Sichuan University, Chengdu, Sichuan 610064 (China); Gong, Min [Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Key Lab of Microelectronics Sichuan Province, Sichuan University, Chengdu, Sichuan 610064 (China); College of Physical Science and Technology, Sichuan University, Chengdu, Sichuan 610064 (China); Willis, Maureen [College of Physical Science and Technology, Sichuan University, Chengdu, Sichuan 610064 (China); Yang, Zhimei [Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Key Lab of Microelectronics Sichuan Province, Sichuan University, Chengdu, Sichuan 610064 (China); Guan, Mingyue [College of Physical Science and Technology, Sichuan University, Chengdu, Sichuan 610064 (China); Li, Yun [Key Laboratory of Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064 (China); Key Lab of Microelectronics Sichuan Province, Sichuan University, Chengdu, Sichuan 610064 (China); College of Physical Science and Technology, Sichuan University, Chengdu, Sichuan 610064 (China)

    2017-04-01

    In this work, a study of the structure modification, induced by high fluence swift heavy ion radiation, of the SiO{sub 2}/Si structures and gate oxide interface in commercial 65 nm MOSFETs is performed. A key and novel point in this study is the specific use of the transmission electron microscopy (TEM) technique instead of the conventional atomic force microscope (AFM) or scanning electron microscope (SEM) techniques which are typically performed following the chemical etching of the sample to observe the changes in the structure. Using this method we show that after radiation, the appearance of a clearly visible thin layer between the SiO{sub 2} and Si is observed presenting as a variation in the TEM intensity at the interface of the two materials. Through measuring the EDX line scans we reveal that the Si:O ratio changed and that this change can be attributed to the migration of the Si towards interface after the Si-O bond is destroyed by the swift heavy ions. For the 65 nm MOSFET sample, the silicon substrate, the SiON insulator and the poly-silicon gate interfaces become blurred under the same irradiation conditions.

  16. The crystal structure of Giardia duodenalis 14-3-3 in the apo form: when protein post-translational modifications make the difference.

    KAUST Repository

    Fiorillo, Annarita

    2014-03-21

    The 14-3-3s are a family of dimeric evolutionary conserved pSer/pThr binding proteins that play a key role in multiple biological processes by interacting with a plethora of client proteins. Giardia duodenalis is a flagellated protozoan that affects millions of people worldwide causing an acute and chronic diarrheal disease. The single giardial 14-3-3 isoform (g14-3-3), unique in the 14-3-3 family, needs the constitutive phosphorylation of Thr214 and the polyglycylation of its C-terminus to be fully functional in vivo. Alteration of the phosphorylation and polyglycylation status affects the parasite differentiation into the cyst stage. To further investigate the role of these post-translational modifications, the crystal structure of the g14-3-3 was solved in the unmodified apo form. Oligomers of g14-3-3 were observed due to domain swapping events at the protein C-terminus. The formation of filaments was supported by TEM. Mutational analysis, in combination with native PAGE and chemical cross-linking, proved that polyglycylation prevents oligomerization. In silico phosphorylation and molecular dynamics simulations supported a structural role for the phosphorylation of Thr214 in promoting target binding. Our findings highlight unique structural features of g14-3-3 opening novel perspectives on the evolutionary history of this protein family and envisaging the possibility to develop anti-giardial drugs targeting g14-3-3.

  17. Vitamin D-metabolites from human plasma and mass spectrometric analysis by fast heavy ion induced desorption

    International Nuclear Information System (INIS)

    Fohlman, J.; Peterson, P.A.

    1982-01-01

    D-vitamin metabolites have been isolated from human serum employing chromatographic techniques. The serum carrier protein for vitamin D (DBP) was first isolated by immunosorbent chromatography. Lipid ligands associated with DBP were then extracted with hexane and separated by high pressure liquid chromatography (HPLC). Detection of vitamin D metabolites by their absorbance of ultraviolet light is not sufficiently sensitive to monitor all vitamin D derivatives from a few millilitres of serum. Therefore, further analyses are necessary to quantitative these compounds. We have begun to develop a mass spectrometric method to achieve a reliable, quantitative procedure. As a first step towards this goal a number of pure samples of vitamin D compounds have been studied in a time-of-flight mass spectrometer based on fast heavy ion induced desorption. All vitamin D compounds examined could be detected and identified by their molecular ion and fragment spectra. (orig.)

  18. 0.5 to 6 MeV Ar ion induced X-ray emission in view to analytical application

    International Nuclear Information System (INIS)

    Tenorio Castilleros, M.D.

    1979-01-01

    A study of the X-ray emission induced by 0.5 to 6 MeV Ar ions has been realized in view of multielemental analytical applications. The historical development of the use of heavy ion induced X-ray emission in analysis and the theoretical background of inner-shell ionization in heavy ion-atom collisions are described. The emission of non characteristic X-rays and the effects related to the penetration of heavy ions in matter are also related. The experimental part contains a description of the experimental devices and of the X-ray spectra fitting method. Thick target yields as a function of the target Z and the Ar ion energy are reported. The analytical possibilities are examined and an application to the analysis of Si and Cl in cadmium telluride crystals is given [fr

  19. Role of sodium ions in the vitrification process: glass matrix modification, slag structure depolymerization, and influence of metal immobilization.

    Science.gov (United States)

    Kuo, Yi-Ming

    2014-07-01

    This study investigates the role of Na ions, a common flux, in the vitrification process. Artificial glass systems composed of Al2O3, CaO, and SiO2 with various Na concentrations were melted at 1450 degrees C. The specimens were cooled by air cooling and water quenching and the metal mobility was evaluated using a sequential extraction procedure. The X-ray diffraction analysis and scanning electron microscopy observations showed that Na ions governed the air-cooled slag's structure. Na ions initially depolymerized CaSiO3-linked chains into CaSiO3 chains, and further cut them into shorter and nonuniform ones, making the slag structure amorphous. With even more Na ions, CaSiO3 chains were divided into single SiO4 tetrahedrons and formed Na-related crystals (Na2Ca3Si2O8 and NaAlSiO4). The phase distributions of Al, Cr, Cu Mn, and Ni showed that Na has a positive effect on the immobilization of heavy metals at suitable concentrations, but a negative effect when in excess amounts. Implications: Vitrification has been widely used to treat hazardous materials. The Na-bearing additives were often used as a flux to improve the melting process. This study described the role of Na played in the vitrification process. The Na ions acted as glass modifier and depolymerize the chain structure of slag. With adequate addition amount of Na ions, the immobilization of heavy metals was improved. The results provided much information about the crystalline phase variation, metal mobility, and surface characteristics while Na serves as a flux.

  20. Application of hydrogen-plasma technology for property modification of silicon and producing the silicon-based structures

    International Nuclear Information System (INIS)

    Fedotov, A.K.; Mazanik, A.V.; Ul'yashin, A.G.; Dzhob, R; Farner, V.R.

    2000-01-01

    Effects of atomic hydrogen on the properties of Czochralski-grown single crystal silicon as well as polycrystalline shaped silicon have been investigated. It was established that the buried defect layers created by high-energy hydrogen or helium ion implantation act as a good getter centers for hydrogen atoms introduced in silicon in the process of hydrogen plasma hydrogenation. Atomic hydrogen was shown to be active as a catalyzer significantly enhancing the rate of thermal donors formation in p-type single crystal silicon. This effect can be used for n-p- and p-n-p-silicon based device structures producing [ru

  1. New Parameterizations for Neutral and Ion-Induced Sulfuric Acid-Water Particle Formation in Nucleation and Kinetic Regimes

    Science.gov (United States)

    Määttänen, Anni; Merikanto, Joonas; Henschel, Henning; Duplissy, Jonathan; Makkonen, Risto; Ortega, Ismael K.; Vehkamäki, Hanna

    2018-01-01

    We have developed new parameterizations of electrically neutral homogeneous and ion-induced sulfuric acid-water particle formation for large ranges of environmental conditions, based on an improved model that has been validated against a particle formation rate data set produced by Cosmics Leaving OUtdoor Droplets (CLOUD) experiments at European Organization for Nuclear Research (CERN). The model uses a thermodynamically consistent version of the Classical Nucleation Theory normalized using quantum chemical data. Unlike the earlier parameterizations for H2SO4-H2O nucleation, the model is applicable to extreme dry conditions where the one-component sulfuric acid limit is approached. Parameterizations are presented for the critical cluster sulfuric acid mole fraction, the critical cluster radius, the total number of molecules in the critical cluster, and the particle formation rate. If the critical cluster contains only one sulfuric acid molecule, a simple formula for kinetic particle formation can be used: this threshold has also been parameterized. The parameterization for electrically neutral particle formation is valid for the following ranges: temperatures 165-400 K, sulfuric acid concentrations 104-1013 cm-3, and relative humidities 0.001-100%. The ion-induced particle formation parameterization is valid for temperatures 195-400 K, sulfuric acid concentrations 104-1016 cm-3, and relative humidities 10-5-100%. The new parameterizations are thus applicable for the full range of conditions in the Earth's atmosphere relevant for binary sulfuric acid-water particle formation, including both tropospheric and stratospheric conditions. They are also suitable for describing particle formation in the atmosphere of Venus.

  2. Response modification for enhanced operation and safety of bridges.

    Science.gov (United States)

    2011-08-01

    This report shows that safe extension of the service life of existing bridge structures is possible through bridge : health monitoring and structural response modification. To understand bridge health monitoring and structural : response modification...

  3. Structure and property modification of an oligochitosan-glycosylated and crosslinked soybean protein generated by microbial transglutaminase.

    Science.gov (United States)

    Song, Chun-Li; Zhao, Xin-Huai

    2014-11-15

    The impacts of oligochitosan glycosylation and crosslinking on the structure and properties of a soybean protein were investigated. The reaction was carried out by transglutaminase with 10 kU kg(-1) protein at pH 7.5 and 37°C for 3h, under a protein content of 40 gl(-1) and a molar ratio of acyl donor to oligochitosan acceptor of 1:3. The modified protein contained glucosamine at a concentration of 12.1 g kg(-1) protein. Electrophoresis and infrared spectroscopy analysis confirmed the modified protein to be crosslinked and glycosylated. Circular dichroism analysis showed the modified protein possessed a decreased α-helix and β-structure. The modified protein exhibited lower surface hydrophobicity and emulsifying activity but higher emulsion stability than the soybean protein, it also had better water and oil binding capacity (12.2g and 3.5 ml g(-1) protein, respectively), and could form a thicker protein outer layer in the oil droplets in emulsion. Transglutaminase-induced oligochitosan glycosylation and crosslinking is thus able to modify soybean proteins. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Modification of structural and optical properties of polyvinyl alcohol/polyethylene glycol thin film by laser irradiation

    Science.gov (United States)

    Nouh, S. A.; Benthami, K.; Abutalib, M. M.

    2016-02-01

    The effect of infrared laser irradiation on the structural and the optical properties of polyvinyl alcohol/polyethylene glycol (PVA/PEG) co-polymer has been investigated. Thin films of PVA/PEG (nearly 50 µm thickness) were irradiated up to 15 J/cm2 of Ga-As laser pulses of 904 nm, 5 W power, and 200-ns pulse duration. The resultant effect of laser irradiation on the structural properties of PVA/PEG has been investigated using X-ray diffraction and Fourier transform infrared spectroscopy (FTIR). Further, the refractive index and the color difference between the exposed samples and the pristine have been studied. FTIR spectroscopy showed that the PVA/PEG samples exhibited degradation under the effect of laser irradiation up to 9 J/cm2, where crosslinking started and continued until 15 J/cm2. The refractive index had a minimum value of 1.5020 at 9 J/cm2, accompanied by a high degree of ordering and maximum value of 1.5640 at 15 J/cm2, with an increase in disordering character due to the degradation and crosslinking formation inside the sample, respectively. Moreover, the color intensity ΔE was greatly increased with increasing the laser fluence, accompanied by a significant increase in the yellow color component.

  5. Electronic excitation induced modifications of structural, electrical and optical properties of Cu-C60 nanocomposite thin films

    Science.gov (United States)

    Inani, H.; Singhal, R.; Sharma, P.; Vishnoi, R.; Ojha, S.; Chand, S.; Sharma, G. D.

    2017-09-01

    High energy ion irradiation significantly affects the size and shape of nanoparticles in composites. Low concentration metal fraction embedded in fullerene matrix in form of nanocomposites was synthesized by thermal co-evaporation method. Swift heavy ion irradiation was performed with 120 MeV Au ion beam on Cu-C60 nanocomposites at different fluences 1 × 1012, 3 × 1012, 6 × 1012, 1 × 1013 and 3 × 1013 ions/cm2. Absorption spectra demonstrated that absorption intensity of nanocomposite thin film was increased whereas absorption modes of fullerene C60 were diminished with fluence. Rutherford backscattering spectroscopy was also performed to estimate the thickness of the film and atomic metal fraction in matrix and found to be 45 nm and 3%, respectively. Transmission electron microscopy was performed for structural and particle size evaluation of Cu nanoparticles (NPs) in fullerene C60 matrix. A growth of Cu nanoparticles is observed at a fluence of 3 × 1013 ions/cm2 with a bi-modal distribution in fullerene C60. Structural evolution of fullerene C60 matrix with increasing fluence of 120 MeV Au ion beam is studied by Raman spectroscopy which shows the amorphization of matrix (fullerene C60) at lower fluence. The growth of Cu nanoparticles is explained using the phenomena of Ostwald ripening.

  6. Reverse osmosis membrane composition, structure and performance modification by bisulphite, iron(III), bromide and chlorite exposure.

    Science.gov (United States)

    Ferrer, O; Gibert, O; Cortina, J L

    2016-10-15

    Reverse osmosis (RO) membrane exposure to bisulphite, chlorite, bromide and iron(III) was assessed in terms of membrane composition, structure and performance. Membrane composition was determined by Rutherford backscattering spectrometry (RBS) and membrane performance was assessed by water and chloride permeation, using a modified version of the solution-diffusion model. Iron(III) dosage in presence of bisulphite led to an autooxidation of the latter, probably generating free radicals which damaged the membrane. It comprised a significant raise in chloride passage (chloride permeation coefficient increased 5.3-5.1 fold compared to the virgin membrane under the conditions studied) rapidly. No major differences in terms of water permeability and membrane composition were observed. Nevertheless, an increase in the size of the network pores, and a raise in the fraction of aggregate pores of the polyamide (PA) layer were identified, but no amide bond cleavage was observed. These structural changes were therefore, in accordance with the transport properties observed. Copyright © 2016 Elsevier Ltd. All rights reserved.

  7. Effects of selenylation modification on structural and antioxidant properties of pectic polysaccharides extracted from Ulmus pumila L.

    Science.gov (United States)

    Lee, Jin-Hye; Lee, Yun-Kyung; Chang, Yoon Hyuk

    2017-11-01

    The present study was carried out to determine the effects of selenylation on structural and antioxidant activities of pectic polysaccharides extracted from Ulmus pumila L. (PPU). Selenylation of PPU (Se-PPU) was synthesized by different concentrations of sodium selenites (0.2, 0.4, 0.6, 0.8, and 1.0g). Structural properties of Se-PPUs were characterized using ICP-OES, HPGPC, FE-SEM, XRD, FT-IR and NMR. After selenylation, the selenium contents and the molecular weights of PPU increased. In FT-IR analysis, a new intensive absorption band at around 667cm -1 was observed in Se-PPU. From 13 C NMR spectra, the new peak at 62.41ppm was found in Se-PPU probably due to the substitution of selenyl groups. In vitro antioxidant activities of all samples were evaluated by reducing power, nitrite scavenging, superoxide dismutase like scavenging activities, hydroxyl radical scavenging activities, and DPPH radical scavenging activities. The antioxidant activities of Se-PPUs were significantly higher than those of PPU. In conclusion, Se-PPU exhibited the potential possibility of the use as an antioxidant in foods and pharmaceuticals. Furthermore, the expanded use of Se-PPU produced from Ulmus sources may be taken in account for better health improvement. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Impact of amylosucrase modification on the structural and physicochemical properties of native and acid-thinned waxy corn starch.

    Science.gov (United States)

    Zhang, Hao; Zhou, Xing; He, Jian; Wang, Tao; Luo, Xiaohu; Wang, Li; Wang, Ren; Chen, Zhengxing

    2017-04-01

    Recombinant amylosucrase from Neisseria polysaccharea was utilized to modify native and acid-thinned starches. The molecular structures and physicochemical properties of modified starches were investigated. Acid-thinned starch displayed much lower viscosity after gelatinization than did the native starch. However, the enzyme exhibited similar catalytic efficiency for both forms of starch. The modified starches had higher proportions of long (DP>33) and intermediate chains (DP 13-33), and X-ray diffraction showed a B-type crystalline structure for all modified starches. With increasing reaction time, the relative crystallinity and endothermic enthalpy of the modified starches gradually decreased, whereas the melting peak temperatures and resistant starch contents increased. Slight differences were observed in thermal parameters, relative crystallinity, and branch chain length distribution between the modified native and acid-thinned starches. Moreover, the digestibility of the modified starches was not affected by acid hydrolysis pretreatment, but was affected by the percentage of intermediate and long chains. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Modification of the electronic, magnetic and structural properties of Nb/Fe(110) multilayers via hydrogen absorption

    International Nuclear Information System (INIS)

    Rehm, Ch.; Fritzsche, H.; Maletta, H.; Klose, F.

    1999-01-01

    Complete text of publication follows. Hydrogen absorption in thin metal films may cause drastic changes of electronic, magnetic and structural properties. The effect of hydrogen loading from the gas phase on Nb/Fe multilayers was investigated (t Nb = 10 - 1000 A). The equilibrium hydrogen concentration in the Nb layers and the hydrogen-induced layer thickness expansion perpendicular to the film plane were determined as function of external hydrogen pressure by means of in-situ neutron reflectivity measurements. In-situ X-ray diffraction experiments performed on the same samples yielded the corresponding expansion of the out-of-plane Nb(110) interplanar spacing and the time-dependence of the charging and decharging process. It was found in all samples that the relative expansion of the Nb layers is considerably larger than the relative increase of the Nb(110) interplanar spacing. The magnetic properties were examined by means of in-situ neutron reflectivity, magnetoresistivity and SQUID measurements. We show that the magnetic exchange coupling between the Fe layers can reversibly be switched by hydrogen absorption/desorption due to changes in the electronic structure of the Nb spacer layers. (author)

  10. Grave pit modifications and wooden structures in the Great Moravian graves and their information potential for cognition of the social structure of the Great Moravian society

    Czech Academy of Sciences Publication Activity Database

    Mazuch, Marian; Hladík, Marek

    2013-01-01

    Roč. 54, č. 2 (2013), s. 45-55 ISSN 1211-7250 R&D Projects: GA ČR GP13-20936P Keywords : Early Middle Ages * Great Moravia * Mikulčice * burial sites * graves * grave pits * burial pits * wooden structures * funeral rite * social structure * GIS * statistics Subject RIV: AC - Archeology, Anthropology, Ethnology

  11. Simultaneous chemical modification and structural transformation of Stöber silica spheres for integration of nanocatalysts

    KAUST Repository

    Yao, Kexin

    2012-01-10

    A synthetic approach has been devised to convert conventional Stöber silica (SiO 2) spheres into a new type of porous structural platform for supporting multicomponent catalysts. With this approach, we have first prepared zinc-doped SiO 2 (Zn-SiO 2) hollow spheres, on which zinc oxide (ZnO) phase and ruthenium (Ru) nanoparticles have been deposited and assembled sequentially in solution phase. A series of complex Ru/ZnO/Zn-SiO 2 nanocatalysts has been thus been integrated onto the zinc-doped SiO 2 supports after additional thermal treatment and reduction. To test their workability under harsh reactive environments, we have further evaluated the above prepared catalysts using arene hydrogenation as model reactions. These integrated nanocatalysts have shown superior activity, high robustness, and easy recovery in the studied heterogeneous catalysis. © 2011 American Chemical Society.

  12. Influence of defect luminescence and structural modification on the electrical properties of Magnesium Doped Zinc Oxide Nanorods

    Science.gov (United States)

    Santoshkumar, B.; Biswas, Amrita; Kalyanaraman, S.; Thangavel, R.; Udayabhanu, G.; Annadurai, G.; Velumani, S.

    2017-06-01

    Magnesium doped zinc oxide nanorod arrays on zinc oxide seed layers were grown by hydrothermal method. X-ray diffraction (XRD) patterns revealed the growth orientation along the preferential (002) direction. The hexagonal morphology was revealed from the field emission scanning electron microscope (FESEM) images. The elemental composition of the samples was confirmed by energy dispersive x-ray analysis spectra (EDS) and mapping dots. Carrier concentration, resistivity and mobility of the samples were obtained by Hall measurements. I-V characteristic curve confirmed the increase in resistivity upon doping. Photoluminescence (PL) spectra exposed the characteristic of UV emission along with defect mediated visible emission in the samples. Electrochemical impedance spectroscopy and cyclic voltammetry were undertaken to study the charge transport property. Owing to the change in the structural parameters and defect concentration the electrical properties of the doped samples were altered.

  13. Systematic structure modifications of imidazo[1,2-a]pyrimidine to reduce metabolism mediated by aldehyde oxidase (AO).

    Science.gov (United States)

    Linton, Angelica; Kang, Ping; Ornelas, Martha; Kephart, Susan; Hu, Qiyue; Pairish, Mason; Jiang, Ying; Guo, Chuangxing

    2011-11-10

    N-{trans-3-[(5-Cyano-6-methylpyridin-2-yl)oxy]-2,2,4,4-tetramethylcyclobutyl}imidazo[1,2-a]pyrimidine-3-carboxamide (1) was recently identified as a full antagonist of the androgen receptor, demonstrating excellent in vivo tumor growth inhibition in castration-resistant prostate cancer (CRPC). However, the imidazo[1,2-a]pyrimidine moiety is rapidly metabolized by aldehyde oxidase (AO). The present paper describes a number of medicinal chemistry strategies taken to avoid the AO-mediated oxidation of this particular system. Guided by an AO protein structure-based model, our investigation revealed the most probable site of AO oxidation and the observation that altering the heterocycle or blocking the reactive site are two of the more effective strategies for reducing AO metabolism. These strategies may be useful for other drug discovery programs.

  14. Response to Extreme Temperatures of Mesoporous Silica MCM-41: Porous Structure Transformation Simulation and Modification of Gas Adsorption Properties.

    Science.gov (United States)

    Zhang, Shenli; Perez-Page, Maria; Guan, Kelly; Yu, Erick; Tringe, Joseph; Castro, Ricardo H R; Faller, Roland; Stroeve, Pieter

    2016-11-08

    Molecular dynamics (MD) and Monte Carlo (MC) simulations were applied together for the first time to reveal the porous structure transformation mechanisms of mesoporous silica MCM-41 subjected to temperatures up to 2885 K. Silica was experimentally characterized to inform the models and enable prediction of changes in gas adsorption/separation properties. MD simulations suggest that the pore closure process is activated by a collective diffusion of matrix atoms into the porous region, accompanied by bond reformation at the surface. Degradation is kinetically limited, such that complete pore closure is postponed at high heating rates. We experimentally observe decreased gas adsorption with increasing temperature in mesoporous silica heated at fixed rates, due to pore closure and structural degradation consistent with simulation predictions. Applying the Kissinger equation, we find a strong correlation between the simulated pore collapse temperatures and the experimental values which implies an activation energy of 416 ± 17 kJ/mol for pore closure. MC simulations give the adsorption and selectivity for thermally treated MCM-41, for N 2 , Ar, Kr, and Xe at room temperature within the 1-10 000 kPa pressure range. Relative to pristine MCM-41, we observe that increased surface roughness due to decreasing pore size amplifies the difference of the absolute adsorption amount differently for different adsorbate molecules. In particular, we find that adsorption of strongly interacting molecules can be enhanced in the low-pressure region while adsorption of weakly interacting molecules is inhibited. This then results in higher selectivity in binary mixture adsorption in mesoporous silica.

  15. Structural and chemical reactivity modifications of a cobalt perovskite induced by Sr-substitution. An in situ XAS study

    International Nuclear Information System (INIS)

    Hueso, Jose L.; Holgado, Juan P.; Pereñíguez, Rosa; Gonzalez-DelaCruz, V.M.; Caballero, Alfonso

    2015-01-01

    LaCoO 3 and La 0.5 Sr 0.5 CoO 3−δ perovskites have been studied by in situ Co K-edge XAS. Although the partial substitution of La(III) by Sr(II) species induces an important increase in the catalytic oxidation activity and modifies the electronic state of the perovskite, no changes could be detected in the oxidation state of cobalt atoms. So, maintaining the electroneutrality of the perovskite requires the generation of oxygen vacancies in the network. The presence of these vacancies explains that the substituted perovskite is now much more reducible than the original LaCoO 3 perovskite. As detected by in situ XAS, after a consecutive reduction and oxidation treatment, the original crystalline structure of the LaCoO 3 perovskite is maintained, although in a more disordered state, which is not the case for the Sr doped perovskite. So, the La 0.5 Sr 0.5 CoO 3−δ perovskite submitted to the same hydrogen reduction treatment produces metallic cobalt, while as determined by in situ XAS spectroscopy the subsequent oxidation treatment yields a Co(III) oxide phase with spinel structure. Surprisingly, no Co(II) species are detected in this new spinel phase. - Highlights: • A Sr-substituted lanthanum cobalt perovskite has been prepared by spray pyrolysis. • It has been established that Co(III) cations are present in both perovskites. • LaCoO 3 is a less reducible phase than the substituted La 0.5 Sr 0.5 CoO 3−δ . • After reoxidation of reduced La 0.5 Sr 0.5 CoO 3−δ , a 100% Co(III) spinel is obtained

  16. Structural and morphological modifications of the Co-thin films caused by magnetic field and pH variation

    International Nuclear Information System (INIS)

    Franczak, Agnieszka; Levesque, Alexandra; Bohr, Frederic; Douglade, Jacques; Chopart, Jean-Paul

    2012-01-01

    Highlights: ► Co electrodeposits were obtained at high electrolyte temperature under applied magnetic field. ► The temperature is commonly used in the industrial process. ► The effects of magnetic field up to 1 T and pH on structure and morphology were investigated. ► The high process temperature enhances HER which is diminishing by the magnetic field application. - Abstract: Cobalt films were deposited by use of the electrochemical process from a cobalt (II) sulfate solution on a titanium electrode and characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD). The experiments at electrolyte temperature of 50 °C were performed which is commonly used in the industrial process. The effects of pH and low uniform magnetic field up to 1 T on structure and morphology changes were investigated. The detected phase composition indicates the presence of both phases: hexagonal centered packed and face centered cubic independent on the pH value and the applied magnetic field amplitude. Calculation of the orientation index of Co phase shows the preferential orientation in the films obtained at higher pH. SEM micro-imagines have shown the nucleus shape transition from coarse-grained to needle-shaped dependent on the application of B-field as well as on the pH variation in the case of higher pH level. Co-films obtained from the electrolyte of low pH were characterized by the fine-grained morphology which was not modified by the influence of magnetic field. AFM images proved the effect on roughness of the Co-films which is closely related with the obtained morphology.

  17. Structural modifications of the salivary conditioning film upon exposure to sodium bicarbonate: implications for oral lubrication and mouthfeel.

    Science.gov (United States)

    Ash, A; Wilde, P J; Bradshaw, D J; King, S P; Pratten, J R

    2016-03-14

    The salivary conditioning film (SCF) that forms on all surfaces in the mouth plays a key role in lubricating the oral cavity. As this film acts as an interface between tongue, enamel and oral mucosa, it is likely that any perturbations to its structure could potentially lead to a change in mouthfeel perception. This is often experienced after exposure to oral hygiene products. For example, consumers that use dentifrice that contain a high concentration of sodium bicarbonate (SB) often report a clean mouth feel after use; an attribute that is clearly desirable for oral hygiene products. However, the mechanisms by which SB interacts with the SCF to alter lubrication in the mouth is unknown. Therefore, saliva and the SCF was exposed to high ionic strength and alkaline solutions to elucidate whether the interactions observed were a direct result of SB, its high alkalinity or its ionic strength. Characteristics including bulk viscosity of saliva and the viscoelasticity of the interfacial salivary films that form at both the air/saliva and hydroxyapatite/saliva interfaces were tested. It was hypothesised that SB interacts with the SCF in two ways. Firstly, the ionic strength of SB shields electrostatic charges of salivary proteins, thus preventing protein crosslinking within the film and secondly; the alkaline pH (≈8.3) of SB reduces the gel-like structure of mucins present in the pellicle by disrupting disulphide bridging of the mucins via the ionization of their cysteine's thiol group, which has an isoelectric point of ≈8.3.

  18. Green fluorescent protein (GFP) color reporter gene visualizes parvovirus B19 non-structural segment 1 (NS1) transfected endothelial modification.

    Science.gov (United States)

    Wurster, Thomas; Pölzelbauer, Catharina; Schönberger, Tanja; Paul, Angela; Seizer, Peter; Stellos, Konstantinos; Schuster, Andreas; Botnar, Rene M; Gawaz, Meinrad; Bigalke, Boris

    2012-01-01

    Human Parvovirus B19 (PVB19) has been associated with myocarditis putative due to endothelial infection. Whether PVB19 infects endothelial cells and causes a modification of endothelial function and inflammation and, thus, disturbance of microcirculation has not been elucidated and could not be visualized so far. To examine the PVB19-induced endothelial modification, we used green fluorescent protein (GFP) color reporter gene in the non-structural segment 1 (NS1) of PVB19. NS1-GFP-PVB19 or GFP plasmid as control were transfected in an endothelial-like cell line (ECV304). The endothelial surface expression of intercellular-adhesion molecule-1 (CD54/ICAM-1) and extracellular matrix metalloproteinase inducer (EMMPRIN/CD147) were evaluated by flow cytometry after NS-1-GFP or control-GFP transfection. To evaluate platelet adhesion on NS-1 transfected ECs, we performed a dynamic adhesion assay (flow chamber). NS-1 transfection causes endothelial activation and enhanced expression of ICAM-1 (CD54: mean ± standard deviation: NS1-GFP vs. control-GFP: 85.3 ± 11.2 vs. 61.6 ± 8.1; PGFP vs. control-GFP: 114 ± 15.3 vs. 80 ± 0.91; PGFP transfected cells. Dynamic adhesion assays showed that adhesion of platelets is significantly enhanced on NS1 transfected ECs when compared to control-GFP (PGFP color reporter gene shows transfection of ECs and may help to visualize NS1-PVB19 induced endothelial activation and platelet adhesion as well as an enhanced monocyte adhesion directly, providing in vitro evidence of possible microcirculatory dysfunction in PVB19-induced myocarditis and, thus, myocardial tissue damage.

  19. Modification of soy protein hydrolysates by Maillard reaction: Effects of carbohydrate chain length on structural and interfacial properties.

    Science.gov (United States)

    Li, Weiwei; Zhao, Haibo; He, Zhiyong; Zeng, Maomao; Qin, Fang; Chen, Jie

    2016-02-01

    This study investigated the effects of carbohydrate chain length on the structural and interfacial properties of the Maillard reaction conjugates of soy protein hydrolysates (Mw>30 kDa). The covalent attachment of sugars to soy peptides was confirmed by amino acid analysis and examination of the Fourier-transform infrared spectra. The results suggested that the emulsion stability of the conjugates increased as the length of the carbohydrate chains increased. The surface activity measurement revealed that the soy peptide-dextran conjugates were closely packed and that each molecule occupied a small area of the interface. It was further confirmed that the soy peptide-dextran conjugates formed a thick adsorbed layer at the oil-water interface, as observed in the confocal laser scanning micrographs. The interfacial layer of soy peptides was rheologically complex with broad linear viscoelastic region and strong elastic modulus, and the soy peptide-dextran conjugates might form multilayer adsorption at the interface. This study suggested that the improved surface properties of the soy peptide-dextran conjugates were a result of the strong membrane formed by the closely packed molecular and multilayer adsorption at the interface, which provided steric hindrance to flocculation. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. Contribution of chemical modifications and isotopic labelling to the establishment of structure-affinity relations of cyclic oligosaccharides

    International Nuclear Information System (INIS)

    Azaroual-Bellanger, Nathalie

    1993-01-01

    The aim of the present work is to synthesize and investigate cyclodextrin derivatives dedicated to the vectorization of drugs. Cyclodextrins are well known for their ability to include hydrophobic molecules in their cavity. Two classes of molecules have been prepared namely cyclodextrins bearing amino-acids, the peptido-cyclodextrins, as models for derivatives dedicated to target receptors, and amphiphilic cyclodextrins (lollipops) bearing an aliphatics chain which could be inserted into pre-organized phases as vesicles or micelles. To investigate the structure and properties of these molecules, Nuclear Magnetic Resonance was used as the analytical tool. Two types of studies have been performed: - First, self-inclusion and complexation phenomena have been showed along with the determination of stoichiometries and association constants. For this purpose, one and two-dimensional NMR (proton and 13 C) were used. - Second, the dynamic study of natural cyclodextrins, derivatives and inclusion complexes was performed using NMR and relaxation studies on deuterium and 13 C nuclei. For this purpose, deuterium labelled analogs have been prepared. (author) [fr

  1. Enhanced radiation resistance through interface modification of nano-structured steels for Gen IV in-core applications

    International Nuclear Information System (INIS)

    Jang, Jinsung; Kang, Suk Hoon; Kim, Min Chul

    2013-06-01

    This project is to increase radiation tolerance of candidate alloys for Gen IV core component through the optimization of grain size and grain boundary characteristics. The focus is on nanocrystalline metal alloys with a fcc crystal structure. The long-term goal is to design and develop bulk nanostructured austenitic steels with enhanced void swelling resistance and substantial ductility, and to enhance their creep resistance at elevated temperatures via grain boundary engineering. An austenitic stainless steel, HT-UPS (high temperature ultra-fine precipitates strengthened) was developed at ORNL, and is expected to show enhanced void swelling resistance through the trapping of point defects at nanometer-sized carbides. Reducing the grain size and increasing the fraction-induced point defects (due to the increased sink area of the grain boundaries), to make bubble nucleation at the boundaries less likely (by reducing the fraction of high-energy boundaries), and to improve the strength and ductility under radiation by producing a higher density of nanometer sized carbides on the boundaries

  2. Effect of modification of isotactic polypropylene by additives of polyamide 6/66 on structural characteristics of composites

    Science.gov (United States)

    Vorontsov, N. V.; Popov, A. A.; Margolin, A. L.

    2017-12-01

    Changes in the supramolecular structure of polymer composites based on isotactic polypropylene (PP) and polyamide 6/66 (PA) are studied depending on the PP : PA ratio. Temperatures and enthalpies of melting and crystallization of both PP and PA and their composites are determined depending on the composition of the mixtures. It was shown that the initial melting point of a composite does not change with increasing PA content in the blends. The crystallization temperature of the mixtures is shown to increase with the addition of PA and becomes much higher than the crystallization temperatures of both PP and PA. The observed effect can be due to a strong interaction between the PP and PA molecules, thus decreasing the molecular mobility and increasing the crystallization temperature. The crystallization and melting of PP-PA mixtures are found to proceed at the close temperatures, although the crystallization and melting temperatures of pure PP and pure PA differ widely. The melting and crystallization enthalpies decrease with increasing PA concentration in the mixtures, which indicates a decrease in the degree of crystallinity of the composite.

  3. Effect of pH on the chemical modification of quercetin and structurally related flavonoids characterized by optical (UV-visible and Raman) spectroscopy.

    Science.gov (United States)

    Jurasekova, Z; Domingo, C; Garcia-Ramos, J V; Sanchez-Cortes, S

    2014-07-07

    In this work we report the study of the chemical modifications undergone by flavonoids, especially by quercetin (QUC), under alkaline conditions by UV-visible absorption, Raman and surface-enhanced Raman scattering (SERS) spectroscopy, the study was performed in aqueous solution and also on Ag nanoparticles (AgNPs). Several processes are involved in the effect of alkaline pH both in solution and on AgNPs: autoxidation affecting mainly the C-ring of the molecule and giving rise to the molecular fragmentation leading to simpler molecular products, and/or the dimerization and further polymerization leading to species with a higher molecular weight. In addition, there exists a clear structure-instability correlation concerning mainly particular groups in the molecule: the C3-OH group in the C-ring, the catechol moiety in the B-ring and the C2=C3 bond also existing in the C-ring. QUC possesses all these groups and exhibits high instability in alkaline solution. The SERS spectra registered at different pH revealed a change in the dimerization protocol of QUC going from the A- and C-rings-like-condensation to B-ring-like-condensation. Increasing the knowledge of the chemical properties of these compounds and determining the structure-activity relationship under specific environmental factors allow us to improve their beneficial properties for health as well as the preservation of Cultural Heritage objects, for example, by preventing their degradation.

  4. Influence of landscape structure and human modifications on insect biomass and bat foraging activity in an urban landscape.

    Science.gov (United States)

    Threlfall, Caragh G; Law, Bradley; Banks, Peter B

    2012-01-01

    Urban landscapes are often located in biologically diverse, productive regions. As such, urbanization may have dramatic consequences for this diversity, largely due to changes in the structure and function of urban communities. We examined the influence of landscape productivity (indexed by geology), housing density and vegetation clearing on the spatial distribution of nocturnal insect biomass and the foraging activity of insectivorous bats in the urban landscape of Sydney, Australia. Nocturnal insect biomass (g) and bat foraging activity were sampled from 113 sites representing backyard, open space, bushland and riparian landscape elements, across urban, suburban and vegetated landscapes within 60 km of Sydney's Central Business District. We found that insect biomass was at least an order of magnitude greater within suburban landscapes in bushland and backyard elements located on the most fertile shale influenced geologies (both plandscapes. Similarly, the feeding activity of bats was greatest in bushland, and riparian elements within suburbs on fertile geologies (p = 0.039). Regression tree analysis indicated that the same three variables explained the major proportion of the variation in insect biomass and bat foraging activity. These were ambient temperature (positive), housing density (negative) and the percent of fertile shale geologies (positive) in the landscape; however variation in insect biomass did not directly explain bat foraging activity. We suggest that prey may be unavailable to bats in highly urbanized areas if these areas are avoided by many species, suggesting that reduced feeding activity may reflect under-use of urban habitats by bats. Restoration activities to improve ecological function and maintain the activity of a diversity of bat species should focus on maintaining and restoring bushland and riparian habitat, particularly in areas with fertile geology as these were key bat foraging habitats.

  5. Influence of landscape structure and human modifications on insect biomass and bat foraging activity in an urban landscape.

    Directory of Open Access Journals (Sweden)

    Caragh G Threlfall

    Full Text Available Urban landscapes are often located in biologically diverse, productive regions. As such, urbanization may have dramatic consequences for this diversity, largely due to changes in the structure and function of urban communities. We examined the influence of landscape productivity (indexed by geology, housing density and vegetation clearing on the spatial distribution of nocturnal insect biomass and the foraging activity of insectivorous bats in the urban landscape of Sydney, Australia. Nocturnal insect biomass (g and bat foraging activity were sampled from 113 sites representing backyard, open space, bushland and riparian landscape elements, across urban, suburban and vegetated landscapes within 60 km of Sydney's Central Business District. We found that insect biomass was at least an order of magnitude greater within suburban landscapes in bushland and backyard elements located on the most fertile shale influenced geologies (both p<0.001 compared to nutrient poor sandstone landscapes. Similarly, the feeding activity of bats was greatest in bushland, and riparian elements within suburbs on fertile geologies (p = 0.039. Regression tree analysis indicated that the same three variables explained the major proportion of the variation in insect biomass and bat foraging activity. These were ambient temperature (positive, housing density (negative and the percent of fertile shale geologies (positive in the landscape; however variation in insect biomass did not directly explain bat foraging activity. We suggest that prey may be unavailable to bats in highly urbanized areas if these areas are avoided by many species, suggesting that reduced feeding activity may reflect under-use of urban habitats by bats. Restoration activities to improve ecological function and maintain the activity of a diversity of bat species should focus on maintaining and restoring bushland and riparian habitat, particularly in areas with fertile geology as these were key bat

  6. Effect of ion-induced processes on characteristics of metal-GaAs phase interfaces

    International Nuclear Information System (INIS)

    Ermolovich, I.B.; Il'in, I.Yu.; Konakova, R.V.; Milenin, V.V.; Naumovets, A.A.

    1996-01-01

    Some features o the interactions between phases in the metal-GaAs structures are studied. The structures were fabricated by condensation of the aluminium atoms and AuGe eutectic alloy on the gallium arsenide surface followed by the low-energy ion-beam treatment. It is shown that the bombardment by inert gas atoms leads to changes in both microstructure and phase composition of the heterocontacts and, as a result, in their electrophysical characteristics. Possible mechanisms of the above effects are discussed. 28 refs., 3 figs

  7. Structural modification of resveratrol leads to increased anti-tumor activity, but causes profound changes in the mode of action

    Energy Technology Data Exchange (ETDEWEB)

    Scherzberg, Maria-Christina; Kiehl, Andreas; Zivkovic, Aleksandra; Stark, Holger [Institute of Pharmaceutical Chemistry, Biozentrum, Goethe University, Max-von-Laue-Str. 9, 60438 Frankfurt am Main (Germany); Stein, Jürgen [Institute of Pharmaceutical Chemistry, Biozentrum, Goethe University, Max-von-Laue-Str. 9, 60438 Frankfurt am Main (Germany); Department of Internal Medicine, Sachsenhausen Hospital, Frankfurt am Main (Germany); Fürst, Robert [Institute of Pharmaceutical Biology, Biozentrum, Goethe University, Max-von-Laue-Str. 9, 60438 Frankfurt am Main (Germany); Steinhilber, Dieter [Institute of Pharmaceutical Chemistry, Biozentrum, Goethe University, Max-von-Laue-Str. 9, 60438 Frankfurt am Main (Germany); Ulrich-Rückert, Sandra, E-mail: sandra.ulrich@em.uni-frankfurt.de [Institute of Pharmaceutical Chemistry, Biozentrum, Goethe University, Max-von-Laue-Str. 9, 60438 Frankfurt am Main (Germany)

    2015-08-15

    (Z)-3,5,4′-Trimethoxystilbene (Z-TMS) is a resveratrol analog with increased antiproliferative activity towards a number of cancer cell lines compared to resveratrol, which has been shown to inhibit tubulin polymerization in vitro. The purpose of this study was to investigate if Z-TMS still shows potential for the prevention of metabolic diseases as known for resveratrol. Cell growth inhibition was determined with IC{sub 50} values for Z-TMS between 0.115 μM and 0.473 μM (resveratrol: 110.7 μM to 190.2 μM). Flow cytometric analysis revealed a G{sub 2}/M arrest after Z-TMS treatment, whereas resveratrol caused S phase arrest. Furthermore, Z-TMS was shown to impair microtubule polymerization. Beneficial effects on lipid accumulation were observed for resveratrol, but not for Z-TMS in an in vitro steatosis model. (E)-Resveratrol was confirmed to elevate cAMP levels, and knockdown of AMPK attenuated the antiproliferative activity, while Z-TMS did not show significant effects in these experiments. SIRT1 and AMPK activities were further measured indirectly via induction of the target gene small heterodimer partner (SHP). Thereby, (E)-resveratrol, but not Z-TMS, showed potent induction of SHP mRNA levels in an AMPK- and SIRT1-dependent manner, as confirmed by knockdown experiments. We provide evidence that Z-TMS does not show beneficial metabolic effects, probably due to loss of activity towards resveratrol target genes. Moreover, our data support previous findings that Z-TMS acts as an inhibitor of tubulin polymerization. These findings confirm that the methylation of resveratrol leads to profound changes in the mode of action, which should be taken into consideration when conducting lead structure optimization approaches. - Highlights: • Methylation of resveratrol leads to profound changes in biologic activity. • Z-TMS does not prevent hepatic steatosis, but inhibits tubulin polymerization. • Resveratrol analog Z-TMS does not influence known targets like

  8. Structure-Guided, Single-Point Modifications in the Phosphinic Dipeptide Structure Yield Highly Potent and Selective Inhibitors of Neutral Aminopeptidases

    Energy Technology Data Exchange (ETDEWEB)

    Vassiliou, Stamatia; Węglarz-Tomczak, Ewelina; Berlicki, Łukasz; Pawełczak, Małgorzata; Nocek, Bogusław; Mulligan, Rory; Joachimiak, Andrzej; Mucha, Artur

    2014-10-09

    Seven crystal structures of alanyl aminopeptidase from Neisseria meningitides (the etiological agent of meningitis, NmAPN) complexed with organophosphorus compounds were resolved to determine the optimal inhibitor-enzyme interactions. The enantiomeric phosphonic acid analogs of Leu and hPhe, which correspond to the P1 amino acid residues of well-processed substrates, were used to assess the impact of the absolute configuration and the stereospecific hydrogen bond network formed between the aminophosphonate polar head and the active site residues on the binding affinity. For the hPhe analog, an imperfect stereochemical complementarity could be overcome by incorporating an appropriate P1 side chain. The constitution of P1'-extended structures was rationally designed and the lead, phosphinic dipeptide hPhePψ[CH2]Phe, was modified in a single position. Introducing a heteroatom/heteroatom-based fragment to either the P1 or P1' residue required new synthetic pathways. The compounds in the refined structure were low nanomolar and subnanomolar inhibitors of N. meningitides, porcine and human APNs, and the reference leucine aminopeptidase (LAP). The unnatural phosphinic dipeptide analogs exhibited a high affinity for monozinc APNs associated with a reasonable selectivity versus dizinc LAP. Another set of crystal structures containing the NmAPN dipeptide ligand were used to verify and to confirm the predicted binding modes; furthermore, novel contacts, which were promising for inhibitor development, were identified, including a π-π stacking interaction between a pyridine ring and Tyr372.

  9. Enzymatic modification of starch

    DEFF Research Database (Denmark)

    Jensen, Susanne Langgård

    In the food industry approaches for using bioengineering are investigated as alternatives to conventional chemical and physical starch modification techniques in development of starches with specific properties. Enzyme-assisted post-harvest modification is an interesting approach to this, since...... it is considered a clean and energy saving technology. This thesis aimed to investigate the effect of using reaction conditions, simulating an industrial process, for enzymatic treatment of starch with branching enzyme (BE) from Rhodothermus obamensis. Thus treatements were conducted at 70°C using very high...... of the obtained products and were correlated to properties of the starch substrates. It was found that the obtained products differed depending on both the conditions used and the properties of the starch. Products of starch from certain origins completely lost their granular structure during the enzyme treatment...

  10. Radiation Resistance of the U(Al, Si)(3) Alloy: Ion-Induced Disordering

    Czech Academy of Sciences Publication Activity Database

    Meshi, L.; Yaniv, G.; Horák, Pavel; Vacík, Jiří; Mykytenko, N.; Rafailov, G.; Dahan, I.; Fuks, D.; Kiv, A.

    2018-01-01

    Roč. 11, č. 2 (2018), č. článku 228. ISSN 1996-1944 R&D Projects: GA ČR(CZ) GBP108/12/G108 Institutional support: RVO:61389005 Keywords : U-Al-Si * ion-irradiation * transmission electron microscopy * structural defects * disordering Subject RIV: JI - Composite Materials OBOR OECD: Composites (including laminates, reinforced plastics, cermets, combined natural and synthetic fibre fabrics Impact factor: 2.654, year: 2016

  11. Structure of the bifunctional methyltransferase YcbY (RlmKL) that adds the m7G2069 and m2G2445 modifications in Escherichia coli 23S rRNA

    DEFF Research Database (Denmark)

    Wang, Kai-Tuo; Desmolaize, Benoit; Nan, Jie

    2012-01-01

    , and this nucleotide remains unmodified in Gram-positive rRNAs. The E.coli YcbY enzyme is the first example of a methyltransferase catalyzing two mechanistically different types of RNA modification, and has been renamed as the Ribosomal large subunit methyltransferase, RlmKL. Our structural and functional data provide...

  12. Heavy ion-induced chromosomal aberrations analyzed by fluorescence in situ hybridization

    Energy Technology Data Exchange (ETDEWEB)

    Durante, M.; Gialanella, G.; Grossi, G.; Pugliese, M. [Univ. ``Federico II``, Naples (Italy). Dept. of Physics]|[INFN, Naples (Italy); Cella, L.; Greco, O. [Univ. ``Federico II``, Naples (Italy). Dept. of Physics; Furusawa, Y. [NIRS, Chiba (Japan); George, K.; Yang, T.C. [NASA Lyndon B. Johnson Space Center, Houston, TX (United States)

    1997-09-01

    We have investigated the effectiveness of heavy ions in the induction of chromosomal aberrations in mammalian cells by the recent technique of fluorescence in situ hybridization (FISH) with whole-chromosome probes. FISH-painting was used both in metaphase and interphase (prematurely condensed) chromosomes. The purpose of our experiments was to address the following problems: (a) the ratio of different types of aberrations as a function of radiation quality (search for biomarkers); (b) the ratio between aberrations scored in interphase and metaphase as a function of radiation quality (role of apoptosis); (c) differences between cytogenetic effects produced by different ions at the same LET (role of track structure). (orig./MG)

  13. An investigation of the structural requirements for ATP hydrolysis and DNA cleavage by the EcoKI Type I DNA restriction and modification enzyme

    Science.gov (United States)

    Roberts, Gareth A.; Cooper, Laurie P.; White, John H.; Su, Tsueu-Ju; Zipprich, Jakob T.; Geary, Paul; Kennedy, Cowan; Dryden, David T. F.

    2011-01-01

    Type I DNA restriction/modification systems are oligomeric enzymes capable of switching between a methyltransferase function on hemimethylated host DNA and an endonuclease function on unmethylated foreign DNA. They have long been believed to not turnover as endonucleases with the enzyme becoming inactive after cleavage. Cleavage is preceded and followed by extensive ATP hydrolysis and DNA translocation. A role for dissociation of subunits to allow their reuse has been proposed for the EcoR124I enzyme. The EcoKI enzyme is a stable assembly in the absence of DNA, so recycling was thought impossible. Here, we demonstrate that EcoKI becomes unstable on long unmethylated DNA; reuse of the methyltransferase subunits is possible so that restriction proceeds until the restriction subunits have been depleted. We observed that RecBCD exonuclease halts restriction and does not assist recycling. We examined the DNA structure required to initiate ATP hydrolysis by EcoKI and find that a 21-bp duplex with single-stranded extensions of 12 bases on either side of the target sequence is sufficient to support hydrolysis. Lastly, we discuss whether turnover is an evolutionary requirement for restriction, show that the ATP hydrolysis is not deleterious to the host cell and discuss how foreign DNA occasionally becomes fully methylated by these systems. PMID:21685455

  14. Structural optimization and evaluation of butenolides as potent antifouling agents: modification of the side chain affects the biological activities of compounds

    KAUST Repository

    Li, Yongxin

    2012-09-01

    A recent global ban on the use of organotin compounds as antifouling agents has increased the need for safe and effective antifouling compounds. In this study, a series of new butenolide derivatives with various amine side chains was synthesized and evaluated for their anti-larval settlement activities in the barnacle, Balanus amphitrite. Side chain modification of butenolide resulted in butenolides 3c-3d, which possessed desirable physico-chemical properties and demonstrated highly effective non-toxic anti-larval settlement efficacy. A structure-activity relationship analysis revealed that varying the alkyl side chain had a notable effect on anti-larval settlement activity and that seven to eight carbon alkyl side chains with a tert-butyloxycarbonyl (Boc) substituent on an amine terminal were optimal in terms of bioactivity. Analysis of the physico-chemical profile of butenolide analogues indicated that lipophilicity is a very important physico-chemical parameter contributing to bioactivity. © 2012 Copyright Taylor and Francis Group, LLC.

  15. Evidence of band structure modification due to Jahn-Teller distortion in LixMn2O4 by photoacoustic spectroscopy

    International Nuclear Information System (INIS)

    Lee, S Thomas; Raveendranath, K; Tomy, Rajive M; George, Nibu A; Jayalekshmi, S; Ravi, Jyotsna

    2007-01-01

    Photoacoustic (PA) spectra of Li 0.9 Mn 2 O 4 , LiMn 2 O 4 and Li 1.1 Mn 2 O 4 at two temperatures, 298 K and 280 K which are, respectively, above and below the Jahn-Teller phase transition temperature, 290 K, are determined. The spectra of LiMn 2 O 4 and Li 1.1 Mn 2 O 4 below the transition temperature are found to be significantly different from their respective spectra above the transition temperature. However, the PA spectra of Li 0.9 Mn 2 O 4 at both these temperatures show only a minor difference between each other compared with the changes occurring in LiMn 2 O 4 and Li 1.1 Mn 2 O 4 . These effects are explained on the basis of the predominant JT tetragonal distortion in cubic Li x Mn 2 O 4 with a high Li content, which brings forth a modification in their electronic structure

  16. Use of small-angle neutron scattering to investigate modifications of internal structure in self-assembled grains of nanoparticles synthesized by spray drying.

    Science.gov (United States)

    Sen, D; Khan, Arshad; Bahadur, J; Mazumder, S; Sapra, B K

    2010-07-01

    Micrometric spherical grains consisting of self-assembled silica nanoparticles have been synthesized by spray drying of colloidal suspension. Inter-particle correlation and available specific surface area of silica and void interfaces, in the assembled grains, were modified by addition of electrolyte in initial colloidal dispersion prior to self-assembly process but keeping the overall spherical shape of the assembled grains un-altered. While the external morphology of the assembled grains was probed by scanning electron microscopy, small-angle neutron scattering technique has been employed to investigate the modifications in the internal structure and the inter-particle correlation inside the assembled grains. It is revealed that a sticky hard sphere type of inter-particle correlation between the constituent particles gets altered to a fractal type of correlation with addition of electrolyte. Further, the specific surface area of the silica-void interface gets somewhat enhanced by addition of electrolyte and particularly at higher electrolyte concentration due to formation of some hollow and buckled assembled grains. Copyright 2010 Elsevier Inc. All rights reserved.

  17. Sputtering and crystalline structure modification of bismuth thin films deposited onto silicon substrates under the impact of 20-160 keV Ar+ ions

    International Nuclear Information System (INIS)

    Mammeri, S.; Ouichaoui, S.; Ammi, H.; Zemih, R.

    2010-01-01

    The sputtering of bismuth thin films induced by 20-160 keV Ar + ions has been studied using Rutherford backscattering spectrometry, scanning electron microscopy and X-ray energy dispersive and diffraction spectroscopy. These techniques revealed increasing modifications of the Bi film surfaces with increasing both ion beam energy and fluence up to their complete deterioration under irradiation conditions E = 160 keV and φ = 1.5 x 10 16 cm -2 , leaving isolated islands of preferred (0 1 2) orientation on the Si substrate. The observed surface morphology and crystalline structure evolutions are likely due to a complex interplay of interaction mechanisms involving both elastic nuclear collisions and inelastic electronic ones. The measured Bi sputtering yields versus Ar + ion fluence for a fixed ion energy exhibit a significant depression at very low φ-values followed by a steady state regime above ∼2.0 x 10 14 cm -2 . Measured sputtering yields versus Ar + ion energy with fixing ion fluence to 1.2 x 10 16 cm -2 in the upper part of the yield saturation regime are also reported. Their comparison to theoretical model and SRIM 2008 Monte Carlo simulation predictions is discussed.

  18. Role of structural modifications of montmorillonite, electrical properties effect, physical behavior of nanocomposite proton conducting membranes for direct methanol fuel cell applications

    Directory of Open Access Journals (Sweden)

    Abidin K. Sainul

    2018-03-01

    Full Text Available Proton exchange membranes have been synthesized from polyimide (PI doped with different contents of montmorillonite (MMT which was obtained by solution casting technique. The enhancement of conductivity was achieved through modification with the MMT. Prepared membranes were systematically characterized in terms of ion exchange capacity, water uptake, methanol uptake, swelling behavior and proton conductivity. Fourier transform infrared spectroscopy and X-ray diffraction measurements were used to confirm the structures of the PI/MMT composite electrolyte membranes. SEM surface morphological images of the composite membranes showed that the MMT nanoclay particles were dispersed uniformly within the membrane what was also reflected in XRD results which indicated a good compatibility of MMT particles with the polymer complex. The TGA spectra showed that the thermal stability of the membrane was reduced by adding MMT into the polymer network. The prepared membrane with 10 wt.% of modified MMT exhibited the highest proton conductivity value of 7.06 × 10-2 S·cm-1 at 70 °C. These results imply the potential application of the PI/MMT composite membranes as improved PEMs for DMFC applications.

  19. Single ion induced surface nanostructures: a comparison between slow highly charged and swift heavy ions.

    Science.gov (United States)

    Aumayr, Friedrich; Facsko, Stefan; El-Said, Ayman S; Trautmann, Christina; Schleberger, Marika

    2011-10-05

    This topical review focuses on recent advances in the understanding of the formation of surface nanostructures, an intriguing phenomenon in ion-surface interaction due to the impact of individual ions. In many solid targets, swift heavy ions produce narrow cylindrical tracks accompanied by the formation of a surface nanostructure. More recently, a similar nanometric surface effect has been revealed for the impact of individual, very slow but highly charged ions. While swift ions transfer their large kinetic energy to the target via ionization and electronic excitation processes (electronic stopping), slow highly charged ions produce surface structures due to potential energy deposited at the top surface layers. Despite the differences in primary excitation, the similarity between the nanostructures is striking and strongly points to a common mechanism related to the energy transfer from the electronic to the lattice system of the target. A comparison of surface structures induced by swift heavy ions and slow highly charged ions provides a valuable insight to better understand the formation mechanisms. © 2011 IOP Publishing Ltd

  20. Antioxidant and ion-induced gelation functions of pectins enabled by polyphenol conjugation.

    Science.gov (United States)

    Ahn, Soohwan; Halake, Kantappa; Lee, Jonghwi

    2017-08-01

    The development of antioxidant polymers through the chemical conjugation of natural polyphenols onto polysaccharides has important applications in biomedical, pharmaceutical, food, and cosmetic fields. Due to their labile characteristics, the covalent conjugation of polyphenols while retaining antioxidant properties has been a challenging task. Herein, four structurally different polyphenols, three with and one without a catechol group, were conjugated onto pectin macromolecules via a simple and efficient preparation method involving epichlorohydrin chemistry. The conjugation reactions were confirmed by FT-IR and UV-vis characterization, and the free radical scavenging assay confirmed that the polyphenols maintained their antioxidant activity after the reaction. The conventional structure-antioxidant property relationship can be applied to the assay results, and hesperidin without a catechol group showed the lowest antioxidant capability. The coordination of multivalent metal ions with polyphenols enabled ionic crosslinking and the moduli of hydrogels depend on the type of polyphenols and their molecular interactions with metal ions. The simplicity of preparation and the resulting unique properties could make the pectin conjugates useful in a wide range of application areas. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Modification of dentin surface to enamel-like structure: A potential strategy for improving dentin bonding durability, desensitizing and self-repairing

    Directory of Open Access Journals (Sweden)

    Hongye Yang

    2014-01-01

    Full Text Available Introduction: Current theories of dentin bonding are based on the concept of "hybrid layer". However, the histological complexity of dentin, as well as the vulnerability of the hybrid layer, goes against the long-term effect of dentin bonding. At the same time, post-operative sensitivity is more likely to occur after traditional adhesive restoration. The Hypothesis: Compared to dentin bonding, enamel bonding exhibits a more optimal immediate and long-term performance, owing to its higher degree of mineralization, well-arranged enamel crystals and the porous structure after etching. Moreover, "enamel hypersensitivity" is never going to happen due to the lack of tubules existing in dentin. In light of this phenomenon, we brought up the concept and the proposal method to form an "enamel-like" dentin, simulating enamel structure to achieve satisfying durability of dentin bonding and obtain good performance for preventing post-operative sensitivity. With the application of mesoporous silicon bi-directionally binding to hydroxyapatite of dentin itself and hydroxyapatite nanorods synthetized in vitro, we may be able to form an enamel-like "functional layer" via ion-regulating self-assembly. Evaluation of Hypothesis: This paper explains how to achieve dentin enamel-like modification by chemical methods, especially, details the strategies and possible mechanisms of the hypothesis. Validation of the hypothesis is more likely to eliminate the adverse effect of dentinal fluid, improve long-term performance of dentin bonding, offer strategies for desensitizing treatment and self-repairing carious-affected dentin, and furthermore, provide the possibility to introduce new theories of dentin bonding.

  2. Quasi-elastic scattering an alternative tool for mapping the fusion barriers for heavy-ion induced fusion reaction

    International Nuclear Information System (INIS)

    Behera, B.R.

    2016-01-01

    Heavy element synthesis through heavy-ion induced fusion reaction is an active field in contemporary nuclear physics. Exact knowledge of fusion barrier is one of the essential parameters for planning any experiments for heavy element production. Theoretically there are many models available to predict the exact barrier. Though these models are successful for predicting the fusion of medium mass nuclei, it somehow fails for predicting the exact location of barrier for fusion of heavy nuclei. Experimental determination of barrier for such reactions is required for future experiments for the synthesis of heavy elements. Traditionally fusion barrier is determined taking a double derivative of fusion excitation function. However, such method is difficult in case of fusion of heavy nuclei due to its very low fusion/capture cross section and its experimental complications. Alternatively fusion barrier can be determined by measuring the quasi-elastic cross section at backward angles. This method can be applied for determining the fusion barrier for the fusion of heavy nuclei. Experimental determination of fusion barrier by different methods and comparison of the fusion excitation function and quasi-elastic scattering methods for the determination of fusion barrier are reviewed. At IUAC, New Delhi recently a program has been started for the measurement of fusion barrier through quasi-elastic scattering methods. The experimental facility and the first results of the experiments carried out with this facility are presented. (author)

  3. Ion-induced adhesion enhancement of Ni films on polyester: Si intermediate layer and 84Kr + implantation

    Science.gov (United States)

    Galuska, A. A.

    1990-02-01

    The influence of a 7 nm Si intermediate layer and 84Kr + implantation on the adhesion of 30 nm Ni films on poly[ethylene terephthalate] (PET) substrates was examined. The objective was to determine if the large (a factor of 20) adhesion increases previously observed for 28Si + implanted Ni/PET could be duplicated using a Si intermediate layer and inert gas ion mixing. Ni/Si/PET specimens were implanted with 84Kr + at substrate temperatures below 100°C to avoid polymer degradation. Substantial bubble and void formation was observed in the implanted specimens. After 1 × 10 16 Kr/cm 2 implantation, a buildup of oxygen in the Si intermediate layer was observed. The Ni that was originally present in the Si layer diffused out of the oxidized Si into the Ni overlayer, leaving a SiO x layer. This oxidized Si layer formed sharp interfaces with both the Ni films and PET substrates. X-ray photoelectron spectroscopy (XPS) analysis shows that the Ni/PET interfacial region consisted of a mixture of Ni 2Si and SiO before ion mixing and a discrete SiO 2 layer after mixing. Adhesion testing of the as-deposited and ion mixed films showed no ion-induced adhesion enhancement. It was concluded that in order to enhance the adhesion of Ni films on PET (or other oxygenated polymers) that the reactive species (Si) must be implanted into both the Ni film and the PET substrate.

  4. Modulation of structure, morphology and wettability of polytetrafluoroethylene surface by low energy ion beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Atta, Ali; Fawzy, Yasser H.A. [Radiation Physics Department, National Center for Radiation Research and Technology (NCRRT), Egyptian Atomic Energy Authority (EAEA) (Egypt); Bek, Alpan, E-mail: bek@metu.edu.tr [Physics Department, Middle East Technical University (METU), Ankara (Turkey); Abdel-Hamid, Hassan M. [Diagnostic Radiology Department, Applied Medical Sciences Faculty, Jazan University (Saudi Arabia); El-Oker, Mohamed M. [Physics Department, Faculty of Science, Al-Azhar University, Cairo (Egypt)

    2013-04-01

    Polytetrafluoroethylene (PTFE) films were irradiated under vacuum with 3 keV Argon ions (Ar{sup +}) and fluences ranging from 0.5 × 10{sup 18} to 2 × 10{sup 18} ions/cm{sup 2}. Ion induced PTFE surface modifications of structural, morphological and wettability nature were studied by means of Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy, atomic force microscopy and force spectroscopy, and contact angle measurements. FTIR analysis indicated defluorination of PTFE due to the rupture of C–C and C–F bonds. The values of droplet contact angle of the irradiated samples decreased gradually with the increasing ion flux, and were found to be very sensitive to the environmental humidity under which the measurements were made. The experimental results show that the surface chemical bond, morphology, and wettability of irradiated PTFE samples depend closely on the argon ion flux.

  5. Analyzing heavy-ion-induced charge collection in Si devices by three-dimensional simulation

    International Nuclear Information System (INIS)

    Dodd, P.E.

    1994-01-01

    Properties of charge collection in Si devices in response to single-ion bombardment have been studied using transient three-dimensional drift-diffusion simulation. In unloaded Si diodes, the funnel effect is particularly strong in lightly-doped materials for high-density strikes such as 100 MeV Fe, and essentially all charge collection is by funnel-assisted drift. This drift collection may occur at time scales as late as several nanoseconds, much later than is traditionally associated with drift. For more heavily-doped materials or lower-density strikes, such as 5-MeV α-particles, drift and diffusion play more equal roles. In epitaxial structures the funnel is truncated by the heavily-doped substrate, collapses quickly, and a great deal of charge is collected at late times by diffusion. Charge collection in Si circuitry is influenced by the circuit external to the struck device. Loading effects on charge collection were studied using passive external circuit elements as well as by mixed-mode simulation, which allows modeling of active external circuitry. Simulations indicate that the funnel can be significantly affected by the inclusion of passive loads, while active loads may prevent any direct charge collection by funneling. Finally, the use of three-dimensional device simulators is presented as a method of analyzing results obtained from focused ion microbeam experiments

  6. Swift heavy ions induced irradiation effects in monolayer graphene and highly oriented pyrolytic graphite

    International Nuclear Information System (INIS)

    Zeng, J.; Yao, H.J.; Zhang, S.X.; Zhai, P.F.; Duan, J.L.; Sun, Y.M.; Li, G.P.; Liu, J.

    2014-01-01

    Monolayer graphene and highly oriented pyrolytic graphite (HOPG) were irradiated by swift heavy ions ( 209 Bi and 112 Sn) with the fluence between 10 11 and 10 14 ions/cm 2 . Both pristine and irradiated samples were investigated by Raman spectroscopy. It was found that D and D′ peaks appear after irradiation, which indicated the ion irradiation introduced damage both in the graphene and graphite lattice. Due to the special single atomic layer structure of graphene, the irradiation fluence threshold Φ th of the D band of graphene is significantly lower ( 11 ions/cm 2 ) than that (2.5 × 10 12 ions/cm 2 ) of HOPG. The larger defect density in graphene than in HOPG indicates that the monolayer graphene is much easier to be damaged than bulk graphite by swift heavy ions. Moreover, different defect types in graphene and HOPG were detected by the different values of I D /I D′ . For the irradiation with the same electronic energy loss, the velocity effect was found in HOPG. However, in this experiment, the velocity effect was not observed in graphene samples irradiated by swift heavy ions

  7. Description and field analysis of a coupled ground-water/surface-water flow model (MODFLOW/BRANCH) with modifications for structures and wetlands in southern Dade County, Florida

    Science.gov (United States)

    Swain, E.D.; Howie, Barbara; Dixon, Joann

    1996-01-01

    A coupled surface-water model (BRANCH) and ground-water model (MODFLOW) model were tested to simulate the interacting wetlands/surface-water/ ground-water system of southern Dade County. Several options created for the MODFLOW ground- ground-water model were used in representing this field situation. The primary option is the MODBRANCH interfacing software, which allows leakage to be accounted for between the MODFLOW ground-water model and the BRANCH dynamic model for simulation of flow in an interconnected network of open channels. A modification to an existing software routine, which is referred to as BCF2, allows cells in MODFLOW to rewet when dry--a requirement in representing the seasonal wetlands in Dade County. A companion to BCF2 is the modified evapotranspiration routine EVT2. The EVT2 routine changes the cells where evapotranspiration occurs, depending on which cells are wet. The Streamlink package represents direct connections between the canals and wetlands at locations where canals open directly into overland flow. Within the BRANCH model, the capability to represent the numerous hydraulic structures, gated spillways, gated culverts, and pumps was added. The application of these modifications to model surface-water/ground-water interactions in southern Dade County demonstrated the usefulness of the coupled MODFLOW/BRANCH model. Ground-water and surface-water flows are both simulated with dynamic models. Flow exchange between models, intermittent wetting and drying, evapotranspiration, and hydraulic structure operations are all represented appropriately. Comparison was made with a simulation using the RIV1 package instead of MODBRANCH to represent the canals. RIV1 represents the canals by user-defined stages, and computes leakage to the aquifer. Greater accuracy in reproducing measured ground- water heads was achieved with MODBRANCH, which also computes dynamic flow conditions in the canals, unlike RIV1. The surface-water integrated flow and transport

  8. Using measurements of the aerosol charging state in determination of the particle growth rate and the proportion of ion-induced nucleation

    Directory of Open Access Journals (Sweden)

    J. Leppä

    2013-01-01

    Full Text Available The fraction of charged nucleation mode particles as a function of particle diameter depends on the particle growth rate and the proportion of particles formed via ion-induced nucleation. In this study we have tested the applicability of recent data analysis methods to determine the growth rate and the proportion of ion-induced nucleation from the measured charged fractions. For this purpose we have conducted a series of aerosol dynamic simulations covering a wide range of atmospheric conditions. The growth rate and initial fraction of charged particles were estimated from simulated data using these methods and compared with the values obtained directly from the simulations. We found that the data analysis methods used in this study should not be used when the nuclei growth rate is less than ~3 nm h−1, or when charged particles grow much more rapidly than neutral ones. Furthermore, we found that the difference in removal rates of neutral and charged particles should be taken into account when estimating the proportion of ion-induced nucleation. Neglecting the higher removal rate of charged particles compared with that of neutral ones could result in an underestimation of the proportion of ion-induced nucleation by up to a factor of 2. This underestimation is further increased if charged particles grow more rapidly than neutral ones. We also provided a simple way of assessing whether these methods are suitable for analyzing data measured under specific conditions. The assessment procedure was illustrated using a few examples of actual measurement sites with a more detailed examination of the typical conditions observed at the SMEAR II station in Hyytiälä, Finland.

  9. Structure de l'amidon de maïs et principaux phénomènes impliqués dans sa modification thermique

    Directory of Open Access Journals (Sweden)

    Malumba, P.

    2011-01-01

    Full Text Available Structures and phenomena occurring during the heat treatment of cornstarch. The structure of cornstarch and the modifications induced during the heat treatments are presented in this review. Current knowledge indicate that the starch granules are semi-crystalline entities composed mainly by amylose and amylopectin, undergoing deep reorganizations during the heat treatments. Gelatinization, glass transitions, relaxation phenomena, retrogradation and the formation of amylose-lipids complexes are the major phenomena involved in these reorganisations, and are the basis of changes of the techno-functional properties of cornstarch-based products during their heat treatment. La rhizosphère est le volume du sol situé au voisinage immédiat des racines des plantes et qui se caractérise par la présence d'exsudats racinaires (rhizodépôts. Ces exsudats sont utilisés par la microflore endémique en tant que signaux chimiques en plus d'être un substrat nutritif disponible pour la croissance et le développement de ces microorganismes dans la rhizosphère. Certaines de ces bactéries du sol, appelées PGPRs (Plant Growth Promoting Rhizobacteria, sont capables de coloniser les racines ou bien encore la rhizosphère, mais à la différence des autres bactéries rhizosphériques elles ont, en retour, un effet bénéfique sur la plante. Cet effet bénéfique peut être direct, ou indirect. La promotion directe de la croissance est le résultat du pouvoir d'acquisition des nutriments ou de la stimulation des hormones de la plante. D'autres mécanismes indirects, mais le plus souvent liés à la croissance des plantes, sont impliqués dans la réduction/suppression des pathogènes des plantes. Cet article décrit les différents mécanismes mis en jeu par les PGPRs dans leur environnement naturel pour influencer favorablement la croissance et la santé des plantes.

  10. Irradiation of zinc single crystal with 500 keV singly-charged carbon ions: surface morphology, structure, hardness, and chemical modifications

    Science.gov (United States)

    Waqas Khaliq, M.; Butt, M. Z.; Saleem, Murtaza

    2017-07-01

    Cylindrical specimens of (1 0 4) oriented zinc single crystal (diameter  =  6 mm and length  =  5 mm) were irradiated with 500 keV C+1 ions with the help of a Pelletron accelerator. Six specimens were irradiated in an ultra-high vacuum (~10‒8 Torr) with different ion doses, namely 3.94  ×  1014, 3.24  ×  1015, 5.33  ×  1015, 7.52  ×  1015, 1.06  ×  1016, and 1.30  ×  1016 ions cm-2. A field emission scanning electron microscope (FESEM) was utilized for the morphological study of the irradiated specimens. Formation of nano- and sub-micron size rods, clusters, flower- and fork-like structures, etc, was observed. Surface roughness of the irradiated specimens showed an increasing trend with the ions dose. Energy dispersive x-ray spectroscopy (EDX) helped to determine chemical modifications in the specimens. It was found that carbon content varied in the range 22.86-31.20 wt.% and that oxygen content was almost constant, with an average value of 10.16 wt.%. The balance content was zinc. Structural parameters, i.e. crystallite size and lattice strain, were determined by Williamson-Hall analysis using x-ray diffraction (XRD) patterns of the irradiated specimens. Both crystallite size and lattice strain showed a decreasing trend with the increasing ions dose. A good linear relationship between crystallite size and lattice strain was observed. Surface hardness depicted a decreasing trend with the ions dose and followed an inverse Hall-Petch relation. FTIR spectra of the specimens revealed that absorption bands gradually diminish as the dose of singly-charged carbon ions is increased from 3.94  ×  1014 ions cm-1 to 1.30  ×  1016 ions cm-1. This indicates progressive deterioration of chemical bonds with the increase in ion dose.

  11. Superhydrophobic cotton by fluorosilane modification

    CSIR Research Space (South Africa)

    Erasmus, E

    2009-12-01

    Full Text Available the treatment with fluorinated or silicon compounds)1-4 and by enhancing the surface roughness with a fractal structure5-8. Cotton, a cellulose-based material, that is greatly hydrophilic, is more benefited when made hydrophobic. Modification of cotton...

  12. Modification of the Argonne tandem

    International Nuclear Information System (INIS)

    Yntema, J.L.

    1978-01-01

    For nuclear structure experiments with heavy ions it is necessary to have ion energies in excess of 5 MeV per nucleon. At the Argonne tandem FN accelerator this was accomplished by the addition of a superconducting linac. Modifications of the FN tandem to improve the performance of the pair is described

  13. Surface topographical and structural analysis of Ag+-implanted polymethylmethacrylate

    International Nuclear Information System (INIS)

    Arif, Shafaq; Rafique, M. Shahid; Saleemi, Farhat; Naab, Fabian; Toader, Ovidiu; Sagheer, Riffat; Bashir, Shazia; Zia, Rehana; Siraj, Khurram; Iqbal, Saman

    2016-01-01

    Specimens of polymethylmethacrylate (PMMA) were implanted with 400-keV Ag + ions at different ion fluences ranging from 1 × 10 14 to 5 × 10 15 ions/cm 2 using a 400-kV NEC ion implanter. The surface topographical features of the implanted PMMA were investigated by a confocal microscope. Modifications in the structural properties of the implanted specimens were analyzed in comparison with pristine PMMA by X-ray diffraction (XRD) and Raman spectroscopy. UV–Visible spectroscopy was applied to determine the effects of ion implantation on optical transmittance of the implanted PMMA. The confocal microscopic images revealed the formation of hillock-like microstructures along the ion track on the implanted PMMA surface. The increase in ion fluence led to more nucleation of hillocks. The XRD pattern confirmed the amorphous nature of pristine and implanted PMMA, while the Raman studies justified the transformation of Ag + -implanted PMMA into amorphous carbon at the ion fluence of ⩾5 × 10 14 ions/cm 2 . Moreover, the decrease in optical transmittance of PMMA is associated with the formation of hillocks and ion-induced structural modifications after implantation.

  14. PERUBAHAN STRUKTUR PATI GARUT (Maranta arundinaceae SEBAGAI AKIBAT MODIFIKASI HIDROLISIS ASAM, PEMOTONGAN TITIK PERCABANGAN DAN SIKLUS PEMANASAN-PENDINGINAN [Structure Changes of Arrowroot (Maranta arundinaceae Starch as Influenced by Acid Hydrolysis, Debranching and Autoclaving-Cooling Cycle Modifications

    Directory of Open Access Journals (Sweden)

    Didah Nur Faridah1*

    2010-12-01

    Full Text Available The effects of lintnerization (2.2 N HCl, 2 hours, debranching with pullulanase (1.3 U/g and 10.4 U/g starch and/or three-auctoclaving-cooling cycles at 121oC for 15 minutes on the changes of arrowroot starch structures were studied. The structural modifications of amylose and amylopectin were measured by Gel Permiation Chromatography (GPC, and the distribution of degree of polimerization (DP was analyzed by Fluorophore-Assisted Capillary Electrophoresis (FACE. The GPC profile of native starch using Toyopearl HW-65S gel gave mainly two fractions. Fraction I (Fr. I was a high molecular weight component and Fraction II (Fr. II was a low molecular weight component. After acid modification, the carbohydrate content of Fr. II increased while that of Fr. I decreased. The amount of DP of 6 to 8 increased in all modified arrowroot starches. The GPC and FACE analyses showed that all starch modification techniques caused the structural changes of amylopectin molecules to form short chain amyloses.

  15. Isomerization and Oxidation in the Complementarity-Determining Regions of a Monoclonal Antibody: A Study of the Modification-Structure-Function Correlations by Hydrogen-Deuterium Exchange Mass Spectrometry.

    Science.gov (United States)

    Yan, Yuetian; Wei, Hui; Fu, Ya; Jusuf, Sutjano; Zeng, Ming; Ludwig, Richard; Krystek, Stanley R; Chen, Guodong; Tao, Li; Das, Tapan K

    2016-02-16

    Chemical modifications can potentially change monoclonal antibody's (mAb) local or global conformation and therefore impact their efficacy as therapeutic drugs. Modifications in the complementarity-determining regions (CDRs) are especially important because they can impair the binding affinity of an antibody for its target and therefore drug potency as a result. In order to understand the impact on mAb attributes induced by specific chemical modifications within the CDR, hydrogen-deuterium exchange mass spectrometry (HDX MS) was used to interrogate the conformational impact of Asp isomerization and Met oxidation in the CDRs of a model monoclonal antibody (mAb1). Our results indicate that despite their proximity to each other, Asp54 isomerization and Met56 oxidation in CDR2 in the heavy chain of mAb1 result in opposing conformational impacts on the local and nearby regions, leading directly to different alterations on antibody-antigen binding affinity. This study revealed direct evidence of local and global conformational changes caused by two of the most common degradation pathways in the CDRs of a mAb and identified correlations between chemical modification, structure, and function of the therapeutic monoclonal antibody.

  16. Synthesis of group 10 metal complexes with a new unsymmetrical PN3P-pincer ligand through ligand post-modification: Structure and reactivity

    KAUST Repository

    Wang, Xiufang

    2017-01-01

    A post-modification strategy are used to synthesize a new class of diimine-amido PN3P-pincer group-10 transition metal complexes. The coordination chemistry and the thermal stabilities of their organometallic derivatives are characterized and investigated.

  17. Crystal structure of the Escherichia coli 23S rRNA:m5C methyltransferase RlmI (YccW) reveals evolutionary links between RNA modification enzymes

    DEFF Research Database (Denmark)

    Sunita, S; Tkaczuk, Karolina L; Purta, Elzbieta

    2008-01-01

    Methylation is the most common RNA modification in the three domains of life. Transfer of the methyl group from S-adenosyl-l-methionine (AdoMet) to specific atoms of RNA nucleotides is catalyzed by methyltransferase (MTase) enzymes. The rRNA MTase RlmI (rRNA large subunit methyltransferase gene I...

  18. An Improved Method for Site-Specific End Modification of Zeolite L for the Formation of Zeolite L and Gold Nanoparticle Self-Assembled Structures

    NARCIS (Netherlands)

    Beierle, John M.; Roswanda, Robby; Erne, Petra M.; Coleman, Anthony C.; Browne, Wesley R.; Feringa, Ben L.

    The ability to site-selectively modify micro- and nanosized particles has allowed for directed self-assembly in two and three dimensions. Site-selective modification of particles can be a complicated task requiring the pre-organization of particles or enhanced particle fabrication methods. The

  19. Behavior Modification in Coaching.

    Science.gov (United States)

    Lynch, Annette Rutt; Stillman, Stephen M.

    1979-01-01

    An example of behavior modification used in athletic coaching is presented. The case study involves a member of a women's basketball team and details the use of behavior modification for both weight reduction and skill improvement. (JMF)

  20. Chemical biology approaches for studying posttranslational modifications.

    Science.gov (United States)

    Yang, Aerin; Cho, Kyukwang; Park, Hee-Sung

    2017-09-13

    Posttranslational modification (PTM) is a key mechanism for regulating diverse protein functions, and thus critically affects many essential biological processes. Critical for systematic study of the effects of PTMs is the ability to obtain recombinant proteins with defined and homogenous modifications. To this end, various synthetic and chemical biology approaches, including genetic code expansion and protein chemical modification methods, have been developed. These methods have proven effective for generating site-specific authentic modifications or structural mimics, and have demonstrated their value for in vitro and in vivo functional studies of diverse PTMs. This review will discuss recent advances in chemical biology strategies and their application to various PTM studies.

  1. Post-Polymerization Modifications of Polymeric Monolithic Columns: A Review

    Directory of Open Access Journals (Sweden)

    Sinéad Currivan

    2014-02-01

    Full Text Available The vast cache of methods used in polymeric monolithic column modification is presented herein, with specific attention to post-polymerization modification reactions. The modification of polymeric monolithic columns is defined and can include the modification of pre-existing surface groups, the addition of polymeric chains or indeed the addition of structures such as nano-particles and nano-structures. The use of these modifications can result in the specific patterning of monoliths, useful in microfluidic device design or in the investigation of modification optimization.

  2. The influence of organic modification on the structural and adsorptive properties of bentonite clay and its application for the removal of lead

    Directory of Open Access Journals (Sweden)

    Stojiljković S.

    2013-01-01

    Full Text Available Organic modification of mineral clay using the monomer ethenyl acetate was performed. The exchange of inorganic interlayer clay cations was achieved using the cationic surfactant Genamine CTAC and Asepsol. Aiming to investigate the influence of organic modifications on adsorptive clay properties, dried composites of clay/ethenyl acetate, with different percentages of clay were soaked in distilled water. The influence of the temperature on the adsorptive properties of organoclays was also followed. The adsorptive properties of the obtained composites of organoclays with Luviskol, Carbopole and purine were investigated along with their capability for removing Pb2+ from water in charged systems. [Projekat Ministarstva nauke Republike Srbije, br. TR 34020, br. 172047 i br. 174007

  3. Large scale analysis of co-existing post-translational modifications in histone tails reveals global fine structure of cross-talk

    DEFF Research Database (Denmark)

    Schwämmle, Veit; Aspalter, Claudia-Maria; Sidoli, Simone

    2014-01-01

    Mass spectrometry (MS) is a powerful analytical method for the identification and quantification of co-existing post-translational modifications in histone proteins. One of the most important challenges in current chromatin biology is to characterize the relationships between co-existing histone...... marks, the order and hierarchy of their deposition, and their distinct biological functions. We developed the database CrossTalkDB to organize observed and reported co-existing histone marks as revealed by MS experiments of histone proteins and their derived peptides. Statistical assessment revealed...... sample-specific patterns for the co-frequency of histone post-translational modifications. We implemented a new method to identify positive and negative interplay between pairs of methylation and acetylation marks in proteins. Many of the detected features were conserved between different cell types...

  4. Modification of chitin as substrates for chitinase

    African Journals Online (AJOL)

    sunny t

    2015-05-06

    Illankovan et al., 2007). The swelling of chitin powder process is expected to help the enzymatic reaction between chitinase and chitin. Possible modification of chitin-chitin can cause structural changes to become more open due to ...

  5. Structural studies of the high-temperature modifications of sodium and silver orthophosphates, II-Na3PO4 and II-Ag3PO4, and of the low-temperature form I-Ag3PO4

    International Nuclear Information System (INIS)

    Newsam, J.M.; Cheetham, A.K.; Tofield, B.C.

    1980-01-01

    The crystal structures of the high-temperature modifications of sodium and silver orthophosphates have been determined using powder neutron diffraction (PND) data. II-Na 3 PO 4 adopts the space group Fm3m with a = 7.512(3) A at 400 0 C. The PO 4 3- group is centred around the origin, but it shows high orientational disorder. The sodium ions occupy the (1/4, 1/4, 1/4) and (1/2, 1/2, 1/2) sites. II-Ag 3 PO 4 , at 650 0 C, is similar with a = 7.722 (5) A. The structure of I-Ag 3 PO 4 at room temperature (P4 - 3n, a = 6.0095 (6) A) has been re-examined by single-crystal X-ray diffraction. The derived model, with R = 0.019 for 116 independent reflections, is in agreement with the latest work reported in the literature. The structure of I-Ag 3 PO 4 at 375 0 C, as determined by PND, has a = 6.061(1) A, and displays no gross modifications from that observed at 25 0 C, although the anisotropic nature of the silver sites is markedly more pronounced at this higher temperature. The cation mobility is discussed in relation to the high-temperature structures. (Auth.)

  6. Heavy-ion induced desorption yields of amorphous carbon films bombarded with 4.2 MeV/u lead ions

    CERN Document Server

    Mahner, E; Küchler, D; Scrivens, R; Costa Pinto, P; Yin Vallgren, C; Bender, M

    2011-01-01

    During the past decade, intense experimental studies on the heavy-ion induced molecular desorption were performed in several particle accelerator laboratories worldwide in order to understand and overcome large dynamic pressure rises caused by lost beam ions. Different target materials and various coatings were studied for desorption and mitigation techniques were applied to heavy-ion accelerators. For the upgrade of the CERN injector complex, a coating of the Super Proton Synchrotron (SPS) vacuum system with a thin film of amorphous carbon is under study to mitigate the electron cloud effect observed during SPS operation with the nominal proton beam for the Large Hadron Collider (LHC). Since the SPS is also part of the heavy-ion injector chain for LHC, dynamic vacuum studies of amorphous carbon films are important to determine their ion induced desorption yields. At the CERN Heavy Ion Accelerator (LINAC 3), carbon-coated accelerator-type stainless steel vacuum chambers were tested for desorption using 4.2 Me...

  7. Comparative study of 150 keV Ar+ and O+ ion implantation induced structural modification on electrical conductivity in Bakelite polymer

    Science.gov (United States)

    Aneesh Kumar, K. V.; Krishnaveni, S.; Asokan, K.; Ranganathaiah, C.; Ravikumar, H. B.

    2018-02-01

    A comparative study of 150 keV argon (Ar+) and oxygen (O+) ion implantation induced microstructural modifications in Bakelite Resistive Plate Chamber (RPC) detector material at different implantation fluences have been studied using Positron Annihilation Lifetime Spectroscopy (PALS). Positron lifetime parameters viz., o-Ps lifetime (τ3) and its intensity (I3) upon lower implantation fluences can be interpreted as the cross-linking and the increased local temperature induced diffusion followed by trapping of ions in the interior polymer voids. The increased o-Ps lifetime (τ3) at higher O+ ion implantation fluences indicates chain scission owing to the oxidation and track formation. This is also justified by the X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) results. The modification in the microstructure and electrical conductivity of Bakelite materials are more upon implantation of O+ ions than Ar+ ions of same energy and fluences. The reduced electrical conductivity of Bakelite polymer material upon ion implantation of both the ions is correlated to the conducting pathways and cross-links in the polymer matrix. The appropriate energy and fluence of implanting ions might reduce the leakage current and hence improve the performance of Bakelite RPC detectors.

  8. Sputtering and surface structure modification of gold thin films deposited onto silicon substrates under the impact of 20–160 keV Ar{sup +} ions

    Energy Technology Data Exchange (ETDEWEB)

    Mammeri, S., E-mail: smammeri@yahoo.fr [Centre de Recherche Nucléaire d’Alger, B.P. 399, 02 Bd. Frantz Fanon, Alger-Gare, Algiers (Algeria); Ouichaoui, S. [Université des Sciences et de la Technologie H. Boumediene (USTHB), Faculté de Physique, Laboratoire SNIRM, B.P. 32, El-Alia, 16111 Bab Ezzouar, Algiers (Algeria); Ammi, H.; Dib, A. [Centre de Recherche Nucléaire d’Alger, B.P. 399, 02 Bd. Frantz Fanon, Alger-Gare, Algiers (Algeria)

    2014-10-15

    Highlights: •Sputter yields were measured for gold thin films under keV Ar{sup +} ion bombardment. •RBS analysis was used to derive energy dependence of sputtering yield. •Surface effects under Ar{sup +} ion irradiation were studied by SEM and XRD analyses. -- Abstract: The induced sputtering and surface state modification of Au thin films bombarded by swift Ar{sup +} ions under normal incident angle have been studied over an energy range of (20–160) keV using three complementary techniques: Rutherford backscattering spectroscopy (RBS), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The sputtering yields determined by RBS measurements using a 2 MeV {sup 4}He{sup +} ion beam were found to be consistent with previous data measured within the Ar{sup +} ion energy region E ⩽ 50 keV, which are thus extended to higher bombarding energies. Besides, the SEM and XRD measurements clearly point out that the irradiated Au film surfaces undergo drastic modifications with increasing the Ar{sup +} ion energy, giving rise to the formation of increasingly sized grains of preferred (1 1 1) crystalline orientations. The relevance of different sputtering yield models for describing experimental data is discussed with invoking the observed surface effects induced by the Ar{sup +} ion irradiation.

  9. Licensing by modification Licensing by modification

    Directory of Open Access Journals (Sweden)

    Veneeta Dayal

    2008-04-01

    Full Text Available Abstract: This paper looks at the phenomena of licensing by modification, whereby an unacceptable noun phrase is redeemed by the presence of a modifier or an unavailable reading for a noun phrase is made available with the addition of a modifier. It argues that an optimal account of such phenomena should derive these effects from the interaction of the meanings of individual expressions in the sentence rather than by positing a formal licensing relation between the modifier and the noun it modifies. The general approach is explicated by considering the distribution of bare plurals in Italian and the availability of generic readings for plural definites in English. The overall goal is a modest one. It seeks to draw attention to properties of modification that go beyond set intersection by focusing on phenomena that have not so far been closely scrutinized in the literature. It uses the particular results to draw some conclusions about questions of general interest.Licensing by modification Abstract: This paper looks at the phenomena of licensing by modification, whereby an unacceptable noun phrase is redeemed by the presence of a modifier or an unavailable reading for a noun phrase is made available with the addition of a modifier. It argues that an optimal account of such phenomena should derive these effects from the interaction of the meanings of individual expressions in the sentence rather than by positing a formal licensing relation between the modifier and the noun it modifies. The general approach is explicated by considering the distribution of bare plurals in Italian and the availability of generic readings for plural definites in English. The overall goal is a modest one. It seeks to draw attention to properties of modification that go beyond set intersection by focusing on phenomena that have not so far been closely scrutinized in the literature. It uses the particular results to draw some conclusions about questions of general

  10. The RNA modification landscape in human disease.

    Science.gov (United States)

    Jonkhout, Nicky; Tran, Julia; Smith, Martin A; Schonrock, Nicole; Mattick, John S; Novoa, Eva Maria

    2017-12-01

    RNA modifications have been historically considered as fine-tuning chemo-structural features of infrastructural RNAs, such as rRNAs, tRNAs, and snoRNAs. This view has changed dramatically in recent years, to a large extent as a result of systematic efforts to map and quantify various RNA modifications in a transcriptome-wide manner, revealing that RNA modifications are reversible, dynamically regulated, far more widespread than originally thought, and involved in major biological processes, including cell differentiation, sex determination, and stress responses. Here we summarize the state of knowledge and provide a catalog of RNA modifications and their links to neurological disorders, cancers, and other diseases. With the advent of direct RNA-sequencing technologies, we expect that this catalog will help prioritize those RNA modifications for transcriptome-wide maps. © 2017 Jonkhout et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.

  11. Permit application modifications

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-11-01

    This document contains the Permit Application Modifications for the Y-12 Industrial Landfill V site on the Oak Ridge Reservation. These modifications include the assessment of stability of the proposed Landfill V under static and loading conditions. Analyses performed include the general slope stability, veneer stability of the bottom liner and cover system, and a liquefaction potential assessment of the foundation soils.

  12. Permit application modifications

    International Nuclear Information System (INIS)

    1995-11-01

    This document contains the Permit Application Modifications for the Y-12 Industrial Landfill V site on the Oak Ridge Reservation. These modifications include the assessment of stability of the proposed Landfill V under static and loading conditions. Analyses performed include the general slope stability, veneer stability of the bottom liner and cover system, and a liquefaction potential assessment of the foundation soils

  13. Surface topographical and structural analysis of Ag{sup +}-implanted polymethylmethacrylate

    Energy Technology Data Exchange (ETDEWEB)

    Arif, Shafaq, E-mail: sarif2005@gmail.com [Department of Physics, Lahore College for Women University, Lahore 54000 (Pakistan); Rafique, M. Shahid [Department of Physics, University of Engineering & Technology, Lahore 54000 (Pakistan); Saleemi, Farhat [Department of Physics, Lahore College for Women University, Lahore 54000 (Pakistan); Naab, Fabian; Toader, Ovidiu [Department of Nuclear Engineering and Radiological Sciences, Michigan Ion Beam Laboratory, University of Michigan, MI 48109-2104 (United States); Sagheer, Riffat [Department of Physics, Lahore College for Women University, Lahore 54000 (Pakistan); Bashir, Shazia [Center for Advanced Studies in Physics (CASP), Government College University, Lahore 54000 (Pakistan); Zia, Rehana [Department of Physics, Lahore College for Women University, Lahore 54000 (Pakistan); Siraj, Khurram; Iqbal, Saman [Department of Physics, University of Engineering & Technology, Lahore 54000 (Pakistan)

    2016-08-15

    Specimens of polymethylmethacrylate (PMMA) were implanted with 400-keV Ag{sup +} ions at different ion fluences ranging from 1 × 10{sup 14} to 5 × 10{sup 15} ions/cm{sup 2} using a 400-kV NEC ion implanter. The surface topographical features of the implanted PMMA were investigated by a confocal microscope. Modifications in the structural properties of the implanted specimens were analyzed in comparison with pristine PMMA by X-ray diffraction (XRD) and Raman spectroscopy. UV–Visible spectroscopy was applied to determine the effects of ion implantation on optical transmittance of the implanted PMMA. The confocal microscopic images revealed the formation of hillock-like microstructures along the ion track on the implanted PMMA surface. The increase in ion fluence led to more nucleation of hillocks. The XRD pattern confirmed the amorphous nature of pristine and implanted PMMA, while the Raman studies justified the transformation of Ag{sup +}-implanted PMMA into amorphous carbon at the ion fluence of ⩾5 × 10{sup 14} ions/cm{sup 2}. Moreover, the decrease in optical transmittance of PMMA is associated with the formation of hillocks and ion-induced structural modifications after implantation.

  14. Modifications at operating nuclear power plants

    International Nuclear Information System (INIS)

    Duffy, T.J.; Gazda, P.A.

    1985-01-01

    Modifications at operating nuclear power plants offer the structural engineer many challenges in the areas of scheduling of work, field adjustments, and engineering staff planning. The scheduling of structural modification work for operating nuclear power plants is normally closely tied to planned or unplanned outages of the plant. Coordination between the structural engineering effort, the operating plant staff, and the contractor who will be performing the modifications is essential to ensure that all work can be completed within the allotted time. Due to the inaccessibility of some areas in operating nuclear power plants or the short time available to perform the structural engineering in the case of an unscheduled outrage, field verification of a design is not always possible prior to initiating the construction of the modification. This requires the structural engineer to work closely with the contractor to promptly resolve problems due to unanticipated interferences or material procurement problems that may arise during the course of construction. The engineering staff planning for structural modifications at an operating nuclear power plant must be flexible enough to permit rapid response to the common ''fire drills,'' but controlled enough to ensure technically correct designs and to minimize the expenditure of man-hours and the resulting engineering cost

  15. The computational nature of memory modification.

    Science.gov (United States)

    Gershman, Samuel J; Monfils, Marie-H; Norman, Kenneth A; Niv, Yael

    2017-03-15

    Retrieving a memory can modify its influence on subsequent behavior. We develop a computational theory of memory modification, according to which modification of a memory trace occurs through classical associative learning, but which memory trace is eligible for modification depends on a structure learning mechanism that discovers the units of association by segmenting the stream of experience into statistically distinct clusters (latent causes). New memories are formed when the structure learning mechanism infers that a new latent cause underlies current sensory observations. By the same token, old memories are modified when old and new sensory observations are inferred to have been generated by the same latent cause. We derive this framework from probabilistic principles, and present a computational implementation. Simulations demonstrate that our model can reproduce the major experimental findings from studies of memory modification in the Pavlovian conditioning literature.

  16. Ion bombardment modification of surfaces

    International Nuclear Information System (INIS)

    Auciello, O.

    1984-01-01

    An historical overview of the main advances in the understanding of bombardment-induced surface topography is presented. The implantation and sputtering mechanisms which are relevant to ion bombardment modification of surfaces and consequent structural, electronic and compositional changes are described. Descriptions of plasma and ion-beam sputtering-induced film formation, primary ion-beam deposition, dual beam techniques, cluster of molecule ion-beam deposition, and modification of thin film properties by ion bombardment during deposition are presented. A detailed account is given of the analytical and computational modelling of topography from the viewpoint of first erosion theory. Finally, an account of the possible application and/or importance of textured surfaces in technologies and/or experimental techniques not considered in previous chapters is presented. refs.; figs.; tabs

  17. Epigenetic Modifications: Therapeutic Potential in Cancer

    Directory of Open Access Journals (Sweden)

    Manisha Sachan

    2015-08-01

    Full Text Available Epigenetic modifications and alterations in chromatin structure and function contribute to the cumulative changes observed as normal cells undergo malignant transformation. These modifications and enzymes (DNA methyltransferases, histone deacetylases, histone methyltransferases, and demethylases related to them have been deeply studied to develop new drugs, epigenome-targeted therapies and new diagnostic tools. Epigenetic modifiers aim to restore normal epigenetic modification patterns through the inhibition of epigenetic modifier enzymes. Four of them (azacitidine, decitabine, vorinostat and romidepsin are approved by the U.S. Food and Drug Administration. This article provides an overview about the known functional roles of epigenetic enzymes in cancer development.

  18. Modifications to POISSON

    International Nuclear Information System (INIS)

    Harwood, L.H.

    1981-01-01

    At MSU we have used the POISSON family of programs extensively for magnetic field calculations. In the presently super-saturated computer situation, reducing the run time for the program is imperative. Thus, a series of modifications have been made to POISSON to speed up convergence. Two of the modifications aim at having the first guess solution as close as possible to the final solution. The other two aim at increasing the convergence rate. In this discussion, a working knowledge of POISSON is assumed. The amount of new code and expected time saving for each modification is discussed

  19. X-ray studies on piroxicam modifications

    International Nuclear Information System (INIS)

    Reck, G.; Bannier, G.; Hoehne, E.

    1988-01-01

    The anti-inflammatory drug piroxicam, 4-hydroxy-2-methyl-N-(2-pyridyl)2H-1,2-benzothiazine-3-car-boxamide-1,1-dioxide, crystallizes in three different forms, two anhydrates and one monohydrate. Crystal structure analyses of the monohydrate and one of the anhydrate were carried out by Bordner et al. and Kojic-Prodic et al., respectively. The results of the analysis of the third piroxicam modification and of an independently performed structure determination of the monohydrate are reported. Molecular structures and hydrogen bonding of all modifications are discussed. (author)

  20. Study of the mechanisms of heavy-ion induced desorption on accelerator-relevant materials; Untersuchung der Mechanismen schwerioneninduzierter Desorption an beschleunigerrelevanten Materialien

    Energy Technology Data Exchange (ETDEWEB)

    Bender, Markus

    2008-02-22

    The ion beam loss induced desorption is a performance limitation for low charge state heavy ion accelerators. If charge exchanged projectile ions get lost onto the beam pipe, desorption of gas is stimulated resulting in a pressure increase inside of the synchrotron and thus, a dramatically reduction of the beam life time. To minimize the amount of desorbed gas an experimental program has been started to measure the desorption yields (released gas molecules per incident ion) of various materials and different projectile ions. The present work is a contribution to the understanding of the physical processes behind the ion beam loss induced desorption. The yield measurements by the pressure rise method have been combined for the rst time with in situ ion beam analysis technologies such as ERDA and RBS. With this unique method the desorption behavior of a sample can be correlated to its surface and bulk properties. The performed experiments with 1,4 MeV/u Xenon-Ions show that the ion induced desorption is mainly a surface effect. Sputtered oxide layers or impurities do not contribute to the desorbed gas significantly. Nevertheless bulk properties play an important role in the desorption strength. Pure metallic samples desorb less gas than isolating materials under swift heavy ion irradiation. From the experimental results it was possible to estimate the desorption yields of various materials under ion bombardment by means of an extended inelastic thermal-spike-model. The extension is the combination of the thermal-spike's temperature map with thermal desorption. Within this model the ion induced desorption can be regarded as the release of adsorbates from a transient overheated spot on the samples surface around the ion impact. Finally a copper substrate with a gold coated surface was developed and proposed as a suitable material for a beam loss collimator with minimum desorption to ensure the performance of GSI's SIS18 in high current beam operation. (orig.)

  1. End Group Modification

    DEFF Research Database (Denmark)

    Jahnsen, Rasmus O; Sandberg-Schaal, Anne; Frimodt-Møller, Niels

    2015-01-01

    modification with hydrophobic moieties led to increased activity towards the Gram-negative Acinetobacter baumannii. Despite increased cytotoxicity against murine fibroblasts and human umbilical vein endothelial cells, the optimized peptide analogues exhibited significantly improved cell selectivity. Overall...

  2. Antimicrobial Modifications of Polymers

    OpenAIRE

    Sedlarik, Vladimir

    2013-01-01

    This chapter is focused on antimicrobial modifications of polymer materials intended for medical devices production. Firstly, a brief introduction into the field of medical application of polymers is presented. Considering the fact that polymer medical devices are often connected with occurrence of nosocomial infections, the next part refers to this phenomenon and its causes. One of the possibilities of reducing of the infection occurrence is aimed at polymer modification. It is a key topic o...

  3. Modification of JRR-2

    International Nuclear Information System (INIS)

    Miyasaka, Yasuhiko

    1978-01-01

    This report gives an outline of some of the main modifications carried out around the Reactor Core on the Research Reactor JRR-2, at the Tokai Research Establishment of JAERI. The JRR-2 was shut down in December 1973, to improve it in heavy water leakage from the metal packing between core tank and support ring, corrosion of the lower shielding plug, and fault in the control-rod mechanism. Main modifications were a standing seal weld at the support ring to stop heavy water leakage, replacement of the reactor top shield and improvement of the helium system. The control-rod assemblies and the refueling devices were replaced by the newly designed ones also. In addition to the modification plan, the irradiated air exhaust system was improved to reduce radioactive argon gas release through the stack. Works were completed successfully in September 1975. But a light water leakage occurred at the stand pipe below the light water tank on November 11, 1975, which was repaired in about 4 months. When considering the operation of above 5,000 hours after the modification, however, the quality of the modification work may be said to be quite satisfactory. The present report in which works to the completion are described may be valuable as a record of reactor modification which is a new experience at JAERI. (auth.)

  4. BIOCHAR MODIFICATION, THERMAL STABILITY AND TOXICITY OF PRODUCTS MODIFICATION

    Directory of Open Access Journals (Sweden)

    Romana FRIEDRICHOVÁ

    2017-12-01

    Full Text Available Biochar is a product obtained from processing of waste biomass. The main application of biochar is in soil and environment remediation. Some new applications of this carbonaceous material take advantage of its adsorption capacity use it as a heterogeneous catalyst for energy storage and conversion etc. This contribution describes thermal stability of the original biochar. It discusses biochar modified by chemical and physical methods including a new compound of biochar-graphene oxide. The purpose of the modifications is to increase its active surface to introduce active functional groups into the carbon structure of biochar in relation to fire safety and toxicity of those products.

  5. Human tRNALys3UUU Is Pre-Structured by Natural Modifications for Cognate and Wobble Codon Binding through Keto-Enol Tautomerism

    Energy Technology Data Exchange (ETDEWEB)

    Vendeix, Franck A.P.; Murphy, IV, Frank V.; Cantara, William A.; Leszczy,; #324; ska, Gra; #380; yna,; Gustilo, Estella M.; Sproat, Brian; Malkiewicz, Andrzej; Agris, Paul F. [Cornell; (NCSU); (Poland); (Integrated DNA); (SUNYA)

    2013-09-27

    Human tRNALys3UUU (htRNALys3UUU) decodes the lysine codons AAA and AAG during translation and also plays a crucial role as the primer for HIV-1 (human immunodeficiency virus type 1) reverse transcription. The posttranscriptional modifications 5-methoxycarbonylmethyl-2-thiouridine (mcm5s2U34), 2-methylthio-N6-threonylcarbamoyladenosine (ms2t6A37), and pseudouridine (Ψ39) in the tRNA's anticodon domain are critical for ribosomal binding and HIV-1 reverse transcription. To understand the importance of modified nucleoside contributions, we determined the structure and function of this tRNA's anticodon stem and loop (ASL) domain with these modifications at positions 34, 37, and 39, respectively (hASLLys3UUU-mcm5s2U34;ms2t6A3739). Ribosome binding assays in vitro revealed that the hASLLys3UUU-mcm5s2U34;ms2t6A3739 bound AAA and AAG codons, whereas binding of the unmodified ASLLys3UUU was barely detectable. The UV hyperchromicity, the circular dichroism, and the structural analyses indicated that Ψ39 enhanced the thermodynamic stability of the ASL through base stacking while ms2t6A37 restrained the anticodon to adopt an open loop conformation that is required for ribosomal binding. The NMR-restrained molecular-dynamics-derived solution structure revealed that the modifications provided an open, ordered loop for codon binding. The crystal structures of the hASLLys3UUU-mcm5s2U34;ms2t6A3739 bound to the 30S ribosomal subunit with each codon in the A site showed that the

  6. Structure modification and numerical study of the moisture-separation performance of special crossunder pipe separators for nuclear power steam turbines

    Energy Technology Data Exchange (ETDEWEB)

    Xinjun, Wang; Peng, Cheng; Jinwei, Xie; Zijie, Zhou [Xi' an Jiaotong University, Xi' an (China)

    2015-08-15

    The present paper investigated the enhancement of moisture-separation efficiency for ordinary special crossunder pipe separators (SCRUPSs) and proposed three structure-modified separators (combined separator, Z-shaped SCRUPSs, and spiral-type SCRUPSs). Deposition mechanisms for droplets with different sizes were considered using commercial CFD flow solver. Results show that three structure modified separators can increase droplet deposition rate to varying degrees. Regarding flow losses, spiral-type SCRUPSs cause the highest increase, with a total pressure loss coefficient of 231%, although it has the best deposition rate improvement. Among the three structure-modified separators, 'Z' shape separator has the best separation performance because of its higher moisture-separation efficiency and lower total pressure loss efficiency. Results could provide theoretical basis for research on and development of this new type of moisture separator.

  7. Human Rights and Behavior Modification

    Science.gov (United States)

    Roos, Philip

    1974-01-01

    Criticisms of behavior modification, which charge that it violates ethical and legal principles, are discussed and reasons are presented to explain behavior modification's susceptibility to attack. (GW)

  8. Modification of Structure and Tribological Properties of the Surface Layer of Metal-Ceramic Composite under Electron Irradiation in the Plasmas of Inert Gases

    Science.gov (United States)

    Ovcharenko, V. E.; Ivanov, K. V.; Mohovikov, A. A.; Yu, B.; Xu, Yu; Zhong, L.

    2018-01-01

    Metal-ceramic composites are the main materials for high-load parts in tribomechanical systems. Modern approaches to extend the operation life of tribomechanical systems are based on increasing the strength and tribological properties of the surface layer having 100 to 200 microns in depth. The essential improvement of the properties occurs when high dispersed structure is formed in the surface layer using high-energy processing. As a result of the dispersed structure formation the more uniform distribution of elastic stresses takes place under mechanical or thermal action, the energy of stress concentrators emergence significantly increases and the probability of internal defects formation reduces. The promising method to form the dispersed structure in the surface layer is pulse electron irradiation in the plasmas of inert gases combining electron irradiation and ion bombardment in one process. The present work reports upon the effect of pulse electron irradiation in plasmas of different inert gases with different atomic mass and ionization energy on the structure and tribological properties of the surface layer of TiC/(Ni-Cr) metal-ceramic composite with the volume ratio of the component being 50:50. It is experimentally shown that high-dispersed heterophase structure with a fraction of nanosized particles is formed during the irradiation. Electron microscopy study reveals that refining of the initial coarse TiC particles occurs via their dissolution in the molten metal binder followed by the precipitation of secondary fine particles in the interparticle layers of the binder. The depth of modified layer and the fraction of nanosized particles increase when the atomic number of the plasma gas increases and ionization energy decreases. The wear resistance of metal-ceramic composite improves in accordance to the formation of nanocrystalline structure in the surface layer.

  9. Structural model for the multisubunit Type IC restriction-modification DNA methyltransferase M.EcoR124I in complex with DNA

    Czech Academy of Sciences Publication Activity Database

    Obarska, A.; Blundell, A.; Feder, M.; Vejsadová, Štěpánka; Šišáková, Eva; Weiserová, Marie; Bujnicki, J. M.; Firman, K.

    2006-01-01

    Roč. 34, č. 7 (2006), s. 1992-2005 ISSN 0305-1048 R&D Projects: GA ČR GA204/03/1011 Institutional research plan: CEZ:AV0Z50200510 Keywords : hsds * molecular motors * crystal structures Subject RIV: EE - Microbiology, Virology Impact factor: 6.317, year: 2006

  10. Micro-Computed-Tomography-Guided Analysis of In Vitro Structural Modifications in Two Types of 45S5 Bioactive Glass Based Scaffolds.

    Science.gov (United States)

    Westhauser, Fabian; Ciraldo, Francesca; Balasubramanian, Preethi; Senger, Anne-Sophie; Schmidmaier, Gerhard; Moghaddam, Arash; Boccaccini, Aldo R

    2017-11-23

    Three-dimensional 45S5 bioactive glass (BG)-based scaffolds are being investigated for bone regeneration. Besides structural properties, controlled time-dependent alteration of scaffold morphology is crucial to achieve optimal scaffold characteristics for successful bone repair. There is no in vitro evidence concerning the dependence between structural characteristics and dissolution behavior of 45S5 BG-based scaffolds of different morphology. In this study, the dissolution behavior of scaffolds fabricated by the foam replica method using polyurethane foam (Group A) and maritime sponge Spongia Agaricina (Group B) as sacrificial templates was analyzed by micro-computed-tomography (µCT). The scaffolds were immersed in Dulbecco's Modified Eagle Medium for 56 days under static cell culture conditions and underwent µCT-analysis initially, and after 7, 14, and 56 days. Group A showed high porosity (91%) and trabecular structure formed by macro-pores (average diameter 692 µm ± 72 µm). Group-B-scaffolds were less porous (51%), revealing an optimal pore size distribution within the window of 110-500 µm pore size diameter, combined with superior mechanical stability. Both groups showed similar structural alteration upon immersion. Surface area and scaffold volume increased whilst density decreased, reflecting initial dissolution followed by hydroxycarbonate-apatite-layer-formation on the scaffold surfaces. In vitro- and/or in vivo-testing of cell-seeded BG-scaffolds used in this study should be performed to evaluate the BG-scaffolds' time-dependent osteogenic properties in relation to the measured in vitro structural changes.

  11. Micro-Computed-Tomography-Guided Analysis of In Vitro Structural Modifications in Two Types of 45S5 Bioactive Glass Based Scaffolds

    Directory of Open Access Journals (Sweden)

    Fabian Westhauser

    2017-11-01

    Full Text Available Three-dimensional 45S5 bioactive glass (BG-based scaffolds are being investigated for bone regeneration. Besides structural properties, controlled time-dependent alteration of scaffold morphology is crucial to achieve optimal scaffold characteristics for successful bone repair. There is no in vitro evidence concerning the dependence between structural characteristics and dissolution behavior of 45S5 BG-based scaffolds of different morphology. In this study, the dissolution behavior of scaffolds fabricated by the foam replica method using polyurethane foam (Group A and maritime sponge Spongia Agaricina (Group B as sacrificial templates was analyzed by micro-computed-tomography (µCT. The scaffolds were immersed in Dulbecco’s Modified Eagle Medium for 56 days under static cell culture conditions and underwent µCT-analysis initially, and after 7, 14, and 56 days. Group A showed high porosity (91% and trabecular structure formed by macro-pores (average diameter 692 µm ± 72 µm. Group-B-scaffolds were less porous (51%, revealing an optimal pore size distribution within the window of 110–500 µm pore size diameter, combined with superior mechanical stability. Both groups showed similar structural alteration upon immersion. Surface area and scaffold volume increased whilst density decreased, reflecting initial dissolution followed by hydroxycarbonate-apatite-layer-formation on the scaffold surfaces. In vitro- and/or in vivo-testing of cell-seeded BG-scaffolds used in this study should be performed to evaluate the BG-scaffolds’ time-dependent osteogenic properties in relation to the measured in vitro structural changes.

  12. Boundary structure modification and magnetic properties of Nd-Fe-B sintered magnets by co-doping with Dy{sub 2}O{sub 3}/S powders

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Fang [Institute for Advanced Materials& Technology, University of Science and Technology Beijing, Beijing 100083 (China); Guo, Leichen [School of Engineering Technology, Purdue University, West Lafayette, Indiana 47907 (United States); Li, Ping [Institute for Advanced Materials& Technology, University of Science and Technology Beijing, Beijing 100083 (China); Zhao, Xuzhe [School of Engineering Technology, Purdue University, West Lafayette, Indiana 47907 (United States); Sui, Yanli [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Guo, Zhimeng, E-mail: guozhimengustb@163.com [Institute for Advanced Materials& Technology, University of Science and Technology Beijing, Beijing 100083 (China); Gao, Xuexu [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)

    2017-05-01

    In this paper, the effect of Dy{sub 2}O{sub 3}/S co-doping on the magnetic properties and microstructure was studied in Nd-Fe-B sintered magnets. With S co-doping, the coercivity increased due to grain boundary modification and Dy selective introduction. Continuous grain boundary phases were formed in the co-doped magnets with smaller grain size. The average grain size after a doping of 0.2 wt% S is 7.25 µm, which is approximately 2.37 µm smaller than that of the S-free sintered magnets(9.62 µm). The coercivity of the Dy{sub 2}O{sub 3}/0.2 wt% S co-doped magnets could be increased from 20.9 to 22.8 kOe with changing the remanence and the maximum magnetic energy product slightly. S precipitates in the Nd-rich phases were hexagonal Nd{sub 2}O{sub 2}S phase. Dy avoided the Nd{sub 2}O{sub 2}S phase in the triple junction region, resulting in more available Dy atoms diffusing into the Nd{sub 2}Fe{sub 14}B phase grains to enhance the anisotropy field. Dy-saving was achieved by forming Nd{sub 2}O{sub 2}S phase in the Dy{sub 2}O{sub 3}/S co-doped magnets. - Highlights: • The average grain size of Dy{sub 2}O{sub 3}/S co-doped magnets is 2.37 μm smaller than that of Dy{sub 2}O{sub 3} doped magnets. • The Dy atoms avoid the Nd{sub 2}O{sub 2}S phases and more of them become available to diffuse into the Nd{sub 2}Fe{sub 14}B phases. • The coercivity reaches maximum when S content is 0.2 wt%, 9% higher than the 20.9 kOe coercivity of the S-free magnets.

  13. Modifications of the chemical structure of phenolics differentially affect physiological activities in pulvinar cells of Mimosa pudica L. II. Influence of various molecular properties in relation to membrane transport.

    Science.gov (United States)

    Rocher, Françoise; Roblin, Gabriel; Chollet, Jean-François

    2017-03-01

    Early prediction of compound absorption by cells is of considerable importance in the building of an integrated scheme describing the impact of a compound on intracellular biological processes. In this scope, we study the structure-activity relationships of several benzoic acid-related phenolics which are involved in many plant biological phenomena (growth, flowering, allelopathy, defense processes). Using the partial least squares (PLS) regression method, the impact of molecular descriptors that have been shown to play an important role concerning the uptake of pharmacologically active compounds by animal cells was analyzed in terms of the modification of membrane potential, variations in proton flux, and inhibition of the osmocontractile reaction of pulvinar cells of Mimosa pudica leaves. The hydrogen bond donors (HBD) and hydrogen bond acceptors (HBA), polar surface area (PSA), halogen ratio (Hal ratio), number of rotatable bonds (FRB), molar volume (MV), molecular weight (MW), and molar refractivity (MR) were considered in addition to two physicochemical properties (logD and the amount of non-dissociated form in relation to pKa). HBD + HBA and PSA predominantly impacted the three biological processes compared to the other descriptors. The coefficient of determination in the quantitative structure-activity relationship (QSAR) models indicated that a major part of the observed seismonasty inhibition and proton flux modification can be explained by the impact of these descriptors, whereas this was not the case for membrane potential variations. These results indicate that the transmembrane transport of the compounds is a predominant component. An increasing number of implicated descriptors as the biological processes become more complex may reflect their impacts on an increasing number of sites in the cell. The determination of the most efficient effectors may lead to a practical use to improve drugs in the control of microbial attacks on plants.

  14. Modifications of gravity.

    Science.gov (United States)

    Skordis, Constantinos

    2011-12-28

    General relativity (GR) is a phenomenologically successful theory that rests on firm foundations, but has not been tested on cosmological scales. The deep mystery of dark energy (and possibly even the requirement of cold dark matter (CDM)) has increased the need for testing modifications to GR, as the inference of such otherwise undetected fluids depends crucially on the theory of gravity. Here, I discuss a general scheme for constructing consistent and covariant modifications to the Einstein equations. This framework is such that there is a clear connection between the modification and the underlying field content that produces it. I argue that this is mandatory for distinguishing modifications of gravity from conventional fluids. I give a non-trivial example, a simple metric-based modification of the fluctuation equations for which the background is exact ΛCDM, but differs from it in the perturbations. I show how this can be generalized and solved in terms of two arbitrary functions. Finally, I discuss future prospects and directions of research.

  15. Ab initio study of the intermolecular potential energy surface in the ion-induced-dipole hydrogen-bonded O2(-)(X2Πg)-H2(X1Σg(+)) complex.

    Science.gov (United States)

    Fawzy, Wafaa M

    2012-01-26

    This work presents the first investigation on the intermolecular potential energy surface of the ground electronic state of the O2(-)(2Πg)-H2(1Σg(+)) complex. High level correlated ab initio calculations were carried out using the Hartree-Fock spin-unrestricted coupled cluster singles and doubles including perturbative triples correction [RHF-UCCSD(T)]/aug-cc-pVXZ levels of calculations, where XZ = DZ, TZ, QZ, and 5Z. Results of full geometry optimization and the intermolecular potential energy surface (IPES) calculations show four equivalent minimum energy structures of L-shaped geometry with Cs symmetry at equilibrium along the 2A″ surface of the complex. For these equilibrium minimum energy structures, the most accurate value for the dissociation energy (De) was calculated as 1407.7 cm(-1), which was obtained by extrapolating the counterpoise (CP) corrected De values to the complete basis set (CBS) limit. This global minimum energy structure is stabilized by an ion-induced-dipole hydrogen bond. Detailed investigations of the IPES show that the collinear structure is unstable, while the C2v geometries present saddle points along the 2A″ surface. The barrier height between the two equivalent structures that differs in whether the hydrogen-bonded hydrogen atom is above or below the axis that connects centers of masses of the H2 and O2(-) moieties within the complex was calculated as 70 cm(-1). This suggests that the complex exhibits large amplitude motion. The barrier height to rotation of the H2 moiety by 180° within the complex is 1020 cm(-1). Anharmonic oscillator calculations predicted a strong H-H stretch fundamental transition at 3807 cm(-1). Results of the current work are expected to stimulate further theoretical and experimental investigations on the nature of intermolecular interactions in complexes that contain the superoxide radical and various closed-shell molecules that model atmospheric and biological molecules. These studies are fundamental

  16. Lignin-carbohydrate complexes from sisal (Agave sisalana) and abaca (Musa textilis): chemical composition and structural modifications during the isolation process.

    Science.gov (United States)

    Del Río, José C; Prinsen, Pepijn; Cadena, Edith M; Martínez, Ángel T; Gutiérrez, Ana; Rencoret, Jorge

    2016-05-01

    Two types of lignins occurred in different lignin-carbohydrate fractions, a lignin enriched in syringyl units, less condensed, preferentially associated with xylans, and a lignin with more guaiacyl units, more condensed, associated with glucans. Lignin-carbohydrate complexes (LCC) were isolated from the fibers of sisal (Agave sisalana) and abaca (Musa textilis) according to a plant biomass fractionation procedure recently developed and which was termed as "universally" applicable to any type of lignocellulosic material. Two LCC fractions, namely glucan-lignin (GL) and xylan-lignin (XL), were isolated and differed in the content and composition of carbohydrates and lignin. In both cases, GL fractions were enriched in glucans and comparatively depleted in lignin, whereas XL fractions were depleted in glucans, but enriched in xylans and lignin. Analysis by two-dimensional Nuclear Magnetic Resonance (2D-NMR) and Derivatization Followed by Reductive Cleavage (DFRC) indicated that the XL fractions were enriched in syringyl (S)-lignin units and β-O-4' alkyl-aryl ether linkages, whereas GL fractions have more guaiacyl (G)-lignin units and less β-O-4' alkyl-aryl ether linkages per lignin unit. The data suggest that the structural characteristics of the lignin polymers are not homogeneously distributed within the same plant and that two different lignin polymers with different composition and structure might be present. The analyses also suggested that acetates from hemicelluloses and the acyl groups (acetates and p-coumarates) attached to the γ-OH of the lignin side chains were extensively hydrolyzed and removed during the LCC fractionation process. Therefore, caution must be paid when using this fractionation approach for the structural characterization of plants with acylated hemicelluloses and lignins. Finally, several chemical linkages (phenylglycosides and benzyl ethers) could be observed to occur between lignin and xylans in these plants.

  17. Impact of the structural anisotropy of La2NiO4+δ on on high temperature surface modifications and diffusion of oxygen

    International Nuclear Information System (INIS)

    Gauquelin, Nicolas

    2010-01-01

    La 2 NiO 4+δ was first studied due to its structural similarities with the High Temperature superconductor La 2 NiO 4+δ and more recently due to its promise as a cathode material in Solid Oxide Fuel Cells as well as an oxygen exchange membrane. It crystallizes in the K 2 NiF 4 layered structure and accommodates highly mobile oxygen at its ground state and is therefore overstoichiometric. During this thesis, pure single crystals of La 2 NiO 4+δ were successfully grown using the floating-zone method, subsequently characterized using neutron and Laue Backscattering diffraction and oriented pieces of single crystal with [100] and [001] orientation were prepared. The surface morphology behavior after long term exposure to high temperature in different atmospheres was observed using microscopy techniques because stability at high temperature is required for application purposes and it was discovered a structural change to nickel-rich phases at T>1173 K. The sensibility of the oxygen non-stoichiometry to cooling was studied and subsequently a new 18 O- 18 O exchange apparatus allowing quenching of the samples using liquid nitrogen was developed. Oxygen selfdiffusion was studied using SIMS in the range 673-873K in both [100] and [001] crystallographic directions. The effect of the disorientation of the sample surface on the determination of the slowest diffusion coefficient was discovered and revealed the very strong anisotropy (>5 orders of magnitude difference) between the different diffusion paths. Finally using HTXRD and oxygen release experiments, it was shown that oxygen diffusion from interstitial oxygen starts to be relevant at 550-600 K and a change of behavior is observed around 700 K, corresponding to a possible change in the diffusion mechanism from interstitial to interstitialcy.

  18. Impact of the structural anisotropy of La{sub 2}NiO{sub 4+δ} on on high temperature surface modifications and diffusion of oxygen

    Energy Technology Data Exchange (ETDEWEB)

    Gauquelin, Nicolas

    2010-11-29

    La{sub 2}NiO{sub 4+δ} was first studied due to its structural similarities with the High Temperature superconductor La{sub 2}NiO{sub 4+δ} and more recently due to its promise as a cathode material in Solid Oxide Fuel Cells as well as an oxygen exchange membrane. It crystallizes in the K{sub 2}NiF{sub 4} layered structure and accommodates highly mobile oxygen at its ground state and is therefore overstoichiometric. During this thesis, pure single crystals of La{sub 2}NiO{sub 4+δ} were successfully grown using the floating-zone method, subsequently characterized using neutron and Laue Backscattering diffraction and oriented pieces of single crystal with [100] and [001] orientation were prepared. The surface morphology behavior after long term exposure to high temperature in different atmospheres was observed using microscopy techniques because stability at high temperature is required for application purposes and it was discovered a structural change to nickel-rich phases at T>1173 K. The sensibility of the oxygen non-stoichiometry to cooling was studied and subsequently a new {sup 18}O-{sup 18}O exchange apparatus allowing quenching of the samples using liquid nitrogen was developed. Oxygen selfdiffusion was studied using SIMS in the range 673-873K in both [100] and [001] crystallographic directions. The effect of the disorientation of the sample surface on the determination of the slowest diffusion coefficient was discovered and revealed the very strong anisotropy (>5 orders of magnitude difference) between the different diffusion paths. Finally using HTXRD and oxygen release experiments, it was shown that oxygen diffusion from interstitial oxygen starts to be relevant at 550-600 K and a change of behavior is observed around 700 K, corresponding to a possible change in the diffusion mechanism from interstitial to interstitialcy.

  19. Influence of Carbon Modification on the Morphological, Structural, and Optical Properties of Zinc Oxide Nanoparticles Synthesized by Pneumatic Spray Pyrolysis Technique

    Directory of Open Access Journals (Sweden)

    R. Taziwa

    2017-01-01

    Full Text Available This paper reveals the influence of doping on the morphological, structural, and optical properties of zinc oxide (ZnO nanoparticles (NPs synthesized by pneumatic spray pyrolysis technique (PSP, using zinc ethoxide ZnO2CH32 as the precursor. The prepared samples were characterized by XRD, HRTEM, SEM-EDX, UV-Vis spectroscopy, and RS. RS analysis has revealed that the unmodified ZnO and carbon modified ZnO samples have characteristic Raman optic modes at 325 cm−1, 373 cm−1, and 432 cm−1 belonging to Wurtzite ZnO structure. The XRD ZnO (C:ZnO NPS have characteristic peaks of hexagonal Wurtzite ZnO structure. HRTEM analysis has revealed that the synthesized ZnO NPs have particle size range of 8.8–11.82 nm. EDX spectra of both unmodified and modified ZnO nanoparticles have revealed prominent peaks at 0.51 keV, 1.01 keV, 1.49 keV, 8.87 keV, and 9.86 keV. The occurrence of these peaks in the EDX spectra endorses the existence of Zn and O atoms in the PSP synthesized ZnO NPs. The UV-Vis spectroscopy has revealed a red shift of the absorption edge, with the increase in C dopant level. The effect of nanocrystallite size and the gradual prominence of C into ZnO matrix due to increase in C dopant level in the PSP synthesized ZnO NPs was meticulously elaborated through Raman spectroscopy analysis.

  20. Investigations on heavy ion induced Single-Event Transients (SETs) in highly-scaled FinFETs

    International Nuclear Information System (INIS)

    Gaillardin, M.; Raine, M.; Paillet, P.; Adell, P.C.; Girard, S.; Duhamel, O.; Andrieu, F.; Barraud, S.; Faynot, O.

    2015-01-01

    We investigate Single-Event Transients (SET) in different designs of multiple-gate devices made of FinFETs with various geometries. Heavy ion experimental results are explained by using a thorough charge collection analysis of fast transients measured on dedicated test structures. Multi-level simulations are performed to get new insights into the charge collection mechanisms in multiple-gate devices. Implications for multiple-gate device design hardening are finally discussed.

  1. Structural modifications in the arterial wall during physiological aging and as a result of diabetes mellitus in a mouse model: are the changes comparable?

    Science.gov (United States)

    Prévost, G; Bulckaen, H; Gaxatte, C; Boulanger, E; Béraud, G; Creusy, C; Puisieux, F; Fontaine, P

    2011-04-01

    Vascular accelerated aging represents the major cause of morbidity and mortality in subjects with diabetes mellitus. In the present study, our aim was to compare premature functional and morphological changes in the arterial wall resulting from streptozotocin (STZ)-induced diabetes mellitus in mice over a short-term period with those that develop during physiological aging. The effect of aminoguanidine (AG) on the prevention of these alterations in the diabetic group was also analyzed. The vascular relaxation response to acetylcholine (ACh) in the mouse was tested in isolated segments of phenylephrine (Phe)-precontracted aorta at 2, 4 and 8 weeks (wk) of STZ-induced diabetes and compare to 12- and 84-wk-old mice. Aortic structural changes were investigated, and receptor for AGE (RAGE) aortic expression was quantified by western blot. Compared to the 12-wk control group (76 ± 5%), significant endothelium-dependant relaxation (EDR) impairment was found in the group of 12-wk-old mice, which underwent a 4-wk diabetes-inducing STZ treatment (12wk-4WD) (52 ± 4%; P aging preventive effect on the structural changes of the arterial wall. Our study compared EDR linked to physiological aging with that observed in the case of STZ-induced diabetes over a short-term period, and demonstrated the beneficial effect of AG. Copyright © 2010 Elsevier Masson SAS. All rights reserved.

  2. Antifungal activity of the ethanolic extracts of Punica granatum L. and evaluation of the morphological and structural modifications of its compounds upon the cells of Candida spp.

    Directory of Open Access Journals (Sweden)

    Paula Cristina Anibal

    2013-09-01

    Full Text Available Ethanolic crude extracts prepared from the arils and seeds, pericarp, peels and from the whole fruit of Punica granatum, known as pomegranate, had their antifungal activity tested against Candida spp. The ethanolic crude extracts were analyzed by Mass Spectrometry and yielded many compounds such as punicalagin and galladydilacton. The extracts from the pericarp and peel showed activity against Candida spp., with MICs of 125 µg/mL. The effect of pericarp and peel extracts upon the morphological and structure of C. albicans and C. krusei were examined by scanning and transmission electron microscopy, with the visualization of an irregular membrane and hyphae, formation of vacuoles and thickening of the cell wall. The data obtained revealed potential antimicrobial activity against yeasts cells of the Candida genus, and the bioactive compounds could be responsible for changes in cell morphology and structure. The data obtained open new perspectives for future research in continuation to this study, where information such as determination of the site of action of the compounds could contribute to an alternative therapy against these organisms.

  3. Antifungal activity of the ethanolic extracts of Punica granatum L. and evaluation of the morphological and structural modifications of its compounds upon the cells of Candida spp

    Science.gov (United States)

    Anibal, Paula Cristina; Peixoto, Iza Teixeira Alves; Foglio, Mary Ann; Höfling, José Francisco

    2013-01-01

    Ethanolic crude extracts prepared from the arils and seeds, pericarp, peels and from the whole fruit of Punica granatum, known as pomegranate, had their antifungal activity tested against Candida spp. The ethanolic crude extracts were analyzed by Mass Spectrometry and yielded many compounds such as punicalagin and galladydilacton. The extracts from the pericarp and peel showed activity against Candida spp., with MICs of 125 μg/mL. The effect of pericarp and peel extracts upon the morphological and structure of C. albicans and C. krusei were examined by scanning and transmission electron microscopy, with the visualization of an irregular membrane and hyphae, formation of vacuoles and thickening of the cell wall. The data obtained revealed potential antimicrobial activity against yeasts cells of the Candida genus, and the bioactive compounds could be responsible for changes in cell morphology and structure. The data obtained open new perspectives for future research in continuation to this study, where information such as determination of the site of action of the compounds could contribute to an alternative therapy against these organisms. PMID:24516425

  4. Stimulation of the photoluminescent properties of CBD-CdS thin films achieved by structural modifications resulting from Ag{sup +} doping

    Energy Technology Data Exchange (ETDEWEB)

    Flores-Pacheco, A.; Contreras-Rascon, J.I.; Castillo, S.J.; Alvarez-Ramos, M.E. [Posgrado en Nanotecnologia, Departamento de Fisica, Universidad de Sonora, Hermosillo (Mexico); Diaz-Reyes, J. [Centro de Investigacion en Biotecnologia Aplicada, Instituto Politecnico Nacional, Tepetitla, Tlaxcala (Mexico); Angel-Vicente, P.D. [Instituto Mexicano del Petroleo, Direccion de Investigacion y Posgrado, Ciudad de Mexico (Mexico); Enriquez, J.P. [Centro de Investigacion y Desarrollo Tecnologico en Energias Renovables, Universidad de Ciencias y Artes de Chiapas, Tuxtla Gutierrez (Mexico)

    2017-08-15

    The present study details the changes in photoluminescence properties stimulated by the structural changes in consequence of doping the II-VI nanocomposite thin-film semiconductor cadmium sulfide (CdS) with the IB metallic ion Ag{sup +}. The synthesis of the matrix and doped semiconductors was performed using low-temperature chemical bath deposition (CBD). The doping percentage of the CdS matrix was determined by energy-dispersive X-ray spectroscopy (EDS) with a value around 3%. The crystallographic study shows a cubic (1 1 1) preferential growth plane for the undoped material. Both X-ray and HRTEM characterizations show the presence of a polycrystalline structure for the Ag{sup +}-doped sample. Measurements of particle size from HRTEM micrographs confirm quantum confinement with a reduction of the average particle size from 5.46 to 4.12 nm in the doped sample. The photoluminescence study shows intense downshifted emissions in the green range of the visible spectrum. This could be due to the shallow electron traps formed by crystalline defects in the lattice, which are induced by the metallic ion. This study also shows higher-energy emissions due to the decrease of the particle size below the effective CdS exciton Bohr radius. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Surface modifications of Ti alloy with tunable hierarchical structures and chemistry for improved metal-polymer interface used in deepwater composite riser

    Science.gov (United States)

    He, Peigang; Chen, Ke; Yang, Jinglei

    2015-02-01

    Ti-based fiber reinforced plastic (Ti-FRP) composites have attracted increasing attentions in the marine and offshore applications due their excellent specific mechanical and physical properties. Among those, interface issues play important role to determine the failure modes of the hybrid composites. In this paper, tunable hierarchical structures and oxidation states on Ti alloy (Ti6Al4V) were achieved via physical and chemical surface treatment techniques including sandblasting, anodization, etching and annealing. Wetability and interfacial bonding strength between the treated Ti alloy surfaces and epoxy resin were systemically investigated in consideration of surface microstructures, oxidation states of Ti, and possible chemical reaction between oxidized Ti and amine. After the combined treatments, the epoxy-adhered specimen showed fully cohesive failure mode in epoxy with the highest shear strength and work of fracture. The great increase in the shear bonding strength was attributed to the nano- to macro-scale hierarchical structure on the Ti alloy surface which resulted in the enhanced adhesive strength between epoxy and adherend in terms of the excellent wettability, significant interfacial chemical reaction and reasonable mechanical interlocking.

  6. Modification of the length and structure of the linker of N(6)-benzyladenosine modulates its selective antiviral activity against enterovirus 71.

    Science.gov (United States)

    Drenichev, Mikhail S; Oslovsky, Vladimir E; Sun, Liang; Tijsma, Aloys; Kurochkin, Nikolay N; Tararov, Vitali I; Chizhov, Alexander O; Neyts, Johan; Pannecouque, Christophe; Leyssen, Pieter; Mikhailov, Sergey N

    2016-03-23

    Very recently, we demonstrated that N(6)-isopentenyladenosine, a cytokinin nucleoside, exerts a potent and selective antiviral effect on the replication of human enterovirus 71. The present study is devoted to the structure optimization of another natural compound: N(6)-benzyladenosine. We mainly focused on the exploration of the size and nature of the linker between the adenine and the phenyl ring, as well as on the necessity of the D-ribose residue. More than 30 analogues of N(6)-benzyladenosine were prepared and their antiviral properties were evaluated. Two main methodologies were used for preparation: N(6)-acetyl-2',3',5'-tri-O-acetyladenosine can be regioselectively alkylated either by alkyl halides under base promoted conditions or by alcohols in Mitsunobu reactions. After deacylation with 4 M PrNH2 in MeOH at room temperature for one day, the desired products were obtained in overall high yields. Analysis of the structure-activity relationship clearly shows that the optimal size of the linker is limited to 2 or 3 atoms (compounds 4-7). 2'-Deoxyadenosine derivatives did not elicit any inhibitory or cytotoxic effect, while 5'-deoxynucleosides still induced some cell protective antiviral activity. Based on these observations, it can be hypothesized that there may be another mechanism that is at the base of the antiviral activity of these compounds against enterovirus 71 besides a possible 5'-triphosphorylation followed by a putative inhibitory effect on RNA synthesis. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  7. Antifungal activity of the ethanolic extracts of Punica granatum L. and evaluation of the morphological and structural modifications of its compounds upon the cells of Candida spp.

    Science.gov (United States)

    Anibal, Paula Cristina; Peixoto, Iza Teixeira Alves; Foglio, Mary Ann; Höfling, José Francisco

    2013-01-01

    Ethanolic crude extracts prepared from the arils and seeds, pericarp, peels and from the whole fruit of Punica granatum, known as pomegranate, had their antifungal activity tested against Candida spp. The ethanolic crude extracts were analyzed by Mass Spectrometry and yielded many compounds such as punicalagin and galladydilacton. The extracts from the pericarp and peel showed activity against Candida spp., with MICs of 125 μg/mL. The effect of pericarp and peel extracts upon the morphological and structure of C. albicans and C. krusei were examined by scanning and transmission electron microscopy, with the visualization of an irregular membrane and hyphae, formation of vacuoles and thickening of the cell wall. The data obtained revealed potential antimicrobial activity against yeasts cells of the Candida genus, and the bioactive compounds could be responsible for changes in cell morphology and structure. The data obtained open new perspectives for future research in continuation to this study, where information such as determination of the site of action of the compounds could contribute to an alternative therapy against these organisms.

  8. Donor–Acceptor Copolymers of Relevance for Organic Photovoltaics: A Theoretical Investigation of the Impact of Chemical Structure Modifications on the Electronic and Optical Properties

    KAUST Repository

    Pandey, Laxman

    2012-08-28

    We systematically investigate at the density functional theory level how changes to the chemical structure of donor-acceptor copolymers used in a number of organic electronics applications influences the intrinsic geometric, electronic, and optical properties. We consider the combination of two distinct donors, where a central five-membered ring is fused on both sides by either a thiophene or a benzene ring, with 12 different acceptors linked to the donor either directly or through thienyl linkages. The interplay between the electron richness/deficiency of the subunits as well as the evolution of the frontier electronic levels of the isolated donors/acceptors plays a significant role in determining the electronic and optical properties of the copolymers. © 2012 American Chemical Society.

  9. Electron beam induced modifications of bismuth sulphide (Bi{sub 2}S{sub 3}) thin films: Structural and optical properties

    Energy Technology Data Exchange (ETDEWEB)

    Subramanian, S. [M. D. T. Hindu College, Tirunelveli 627 010 (India); Balaji, M.; Chithra lekha, P. [Department of Physics, Manonmaniam Sundaranar University, Tirunelveli 627 012, Tamil Nadu (India); Sanjeev, Ganesh [Microtron Centre, Mangalore University, Mangalore 574 199 (India); Subramanian, E. [Department of Chemistry, Manonmaniam Sundaranar University, Tirunelveli 627 012 (India); Pathinettam Padiyan, D., E-mail: dppadiyan@sancharnet.i [Department of Physics, Manonmaniam Sundaranar University, Tirunelveli 627 012, Tamil Nadu (India)

    2010-11-15

    Thin films of Bi{sub 2}S{sub 3} prepared by electrodeposition method are subjected to electron beam irradiation for different doses from 0 to 100 kGy in steps of 20 kGy in air at room temperature. The changes in structural, surface morphological and optical properties that occurred before and after irradiation in Bi{sub 2}S{sub 3} thin films are studied using X-ray diffraction, scanning electron microscopy and UV-vis spectroscopy. It is shown that electron irradiation can be used as a tool to decrease the crystallite size of the irradiated films from 418 to 285 A as the dose varies from 20 to 100 kGy. The decrease in crystallinity of the films leading to the band gap energy of the films get blue shifted from unirradiated films. These results are explained in the light of thermal spike model.

  10. Improving the antiprotozoal effect of saponins in the rumen by combination with glycosidase inhibiting iminosugars or by modification of their chemical structure.

    Directory of Open Access Journals (Sweden)

    Eva Ramos-Morales

    Full Text Available The antiprotozoal effect of saponins is transitory, as when saponins are deglycosylated to sapogenins by rumen microorganisms they become inactive. We hypothesised that the combination of saponins with glycosidase-inhibiting iminosugars might potentially increase the effectiveness of saponins over time by preventing their deglycosylation in the rumen. Alternatively, modifying the structure of the saponins by substituting the sugar moiety with other small polar residues might maintain their activity as the sugar substitute would not be enzymatically cleaved. The aim of this in vitro study was to evaluate the acute antiprotozoal effect and the stability of this effect over a 24 h incubation period using ivy saponins, a stevia extract rich in iminosugars, ivy saponins with stevia extract, and a chemically modified ivy saponin, hederagenin bis-succinate (HBS. The effects on fermentation parameters and rumen bacterial communities were also studied. Ivy saponins with stevia and HBS had a greater antiprotozoal effect than ivy saponins, and this effect was maintained after 24 h of incubation (P<0.001. The combination of ivy and stevia extracts was more effective in shifting the fermentation pattern towards higher propionate (+39% and lower butyrate (-32% and lower ammonia concentration (-64% than the extracts incubated separately. HBS caused a decrease in butyrate (-45% and an increase in propionate (+43% molar proportions. However, the decrease in ammonia concentration (-42% observed in the presence of HBS was less than that caused by ivy saponins, either alone or with stevia. Whereas HBS and stevia impacted on bacterial population in terms of community structure, only HBS had an effect in terms of biodiversity (P<0.05. It was concluded that ivy saponins with stevia and the modified saponin HBS had a strong antiprotozoal effect, although they differed in their effects on fermentation parameters and bacteria communities. Ivy saponins combined with an

  11. Improving the antiprotozoal effect of saponins in the rumen by combination with glycosidase inhibiting iminosugars or by modification of their chemical structure

    Science.gov (United States)

    de la Fuente, Gabriel; Nash, Robert J.; Braganca, Radek; Duval, Stephane; Bouillon, Marc E.; Lahmann, Martina; Newbold, C. Jamie

    2017-01-01

    The antiprotozoal effect of saponins is transitory, as when saponins are deglycosylated to sapogenins by rumen microorganisms they become inactive. We hypothesised that the combination of saponins with glycosidase-inhibiting iminosugars might potentially increase the effectiveness of saponins over time by preventing their deglycosylation in the rumen. Alternatively, modifying the structure of the saponins by substituting the sugar moiety with other small polar residues might maintain their activity as the sugar substitute would not be enzymatically cleaved. The aim of this in vitro study was to evaluate the acute antiprotozoal effect and the stability of this effect over a 24 h incubation period using ivy saponins, a stevia extract rich in iminosugars, ivy saponins with stevia extract, and a chemically modified ivy saponin, hederagenin bis-succinate (HBS). The effects on fermentation parameters and rumen bacterial communities were also studied. Ivy saponins with stevia and HBS had a greater antiprotozoal effect than ivy saponins, and this effect was maintained after 24 h of incubation (Pstevia extracts was more effective in shifting the fermentation pattern towards higher propionate (+39%) and lower butyrate (-32%) and lower ammonia concentration (-64%) than the extracts incubated separately. HBS caused a decrease in butyrate (-45%) and an increase in propionate (+43%) molar proportions. However, the decrease in ammonia concentration (-42%) observed in the presence of HBS was less than that caused by ivy saponins, either alone or with stevia. Whereas HBS and stevia impacted on bacterial population in terms of community structure, only HBS had an effect in terms of biodiversity (Pstevia and the modified saponin HBS had a strong antiprotozoal effect, although they differed in their effects on fermentation parameters and bacteria communities. Ivy saponins combined with an iminosugar-rich stevia extract and/or HBS should be evaluated to determine their antiprotozoal

  12. Tumour necrosis factor blockade for the treatment of erosive osteoarthritis of the interphalangeal finger joints: a double blind, randomised trial on structure modification.

    Science.gov (United States)

    Verbruggen, Gust; Wittoek, Ruth; Vander Cruyssen, Bert; Elewaut, Dirk

    2012-06-01

    Adalimumab blocks the action of tumor necrosis factor-α and reduces disease progression in rheumatoid arthritis and psoriatic arthritis. The effects of adalimumab in controlling progression of structural damage in erosive hand osteoarthritis (HOA) were assessed. Sixty patients with erosive HOA on radiology received 40 mg adalimumab or placebo subcutaneously every two weeks during a 12-month randomized double-blind trial. Response was defined as the reduction in progression of structural damage according to the categorical anatomic phase scoring system. Furthermore, subchondral bone, bone plate erosion, and joint-space narrowing were scored according to the continuous Ghent University Score System (GUSSTM). The disease appeared to be active since 40.0% and 26,7% of patients out of the placebo and adalimumab group, respectively, showed at least one new interphalangeal (IP) joint that became erosive during the 12 months follow-up. These differences were not significant and the overall results showed no effect of adalimumab. Risk factors for progression were then identified and the presence of palpable soft tissue swelling at baseline was recognized as the strongest predictor for erosive progression. In this subpopulation at risk, statistically significant less erosive evolution on the radiological image (3.7%) was seen in the adalimumab treated group compared to the placebo group (14.5%) (P = 0.009). GUSSTM scoring confirmed a less rapid rate of mean increase in the erosion scores during the first 6 months of treatment in patients in adalimumab-treated patients. Palpable soft tissue swelling in IP joints in patients with erosive HOA is a strong predictor for erosive progression. In these joints adalimumab significantly halted the progression of joint damage compared to placebo.

  13. Behavior Modification: Education's Watergate.

    Science.gov (United States)

    Carrison, Muriel Paskin

    Several of the theoretical and experimental assumptions relating to behavior modification are examined and criticized: (1) the human mind can only be understood by observing and measuring the functional behavior it causes, (2) performance can be equated with learning, (3) reward systems and token economies improve intrinsic learning, and (4) all…

  14. Modifications to nuclear power plants. Safety guide

    International Nuclear Information System (INIS)

    2004-01-01

    This Safety Guide was prepared under the IAEA's programme for safety standards for nuclear power plants. It supplements Section 7 of the Safety Requirements publication on Safety of Nuclear Power Plants: Operation, which establishes the safety requirements for the modification of nuclear power plants. Reasons for carrying out modifications to nuclear power plants may include: (1) maintaining or strengthening existing safety provisions and thus maintaining consistency with or improving on the current design. (2) recovering from plant faults. (3) improving the thermal performance or increasing the power rating of the plant. (4) increasing the maintainability of the plant, reducing the radiation exposure of personnel or reducing the costs of plant maintenance. And (5) extending the design life of the plant. Most modifications, made on the basis of operating experience, are intended to improve on the design or to improve operational performance and flexibility. Some are rendered necessary by new regulatory requirements, ageing of the plant or obsolescence of equipment. However, the benefits of regularly updating the plant design can be jeopardized if modifications are not kept under rigorous control throughout the lifetime of the plant. The need to reduce costs and improve efficiency, in combination with changes to the structure of the electricity generation sector of the economy in many countries, has led many companies to make changes in the structure of the operating organization for nuclear power plants. Whatever the reason for such organizational changes, consideration should be given to the effects of those changes with the aim of ensuring that they would have no impacts that would compromise the safety of the plant. The objective of this Safety Guide is to provide guidance and recommendations on controlling activities relating to modifications at nuclear power plants in order to reduce risk and to ensure that the configuration of the plant is at all times under

  15. Sustainable Energy Solutions Task 2.0: Wind Turbine Reliability and Maintainability Enhancement through System-wide Structure Health Monitoring and Modifications to Rotating Components

    Energy Technology Data Exchange (ETDEWEB)

    Twomey, Janet M. [Wichita State Univ., Wichita, KS (United States)

    2010-04-30

    An evaluation of nondestructive structural health monitoring methods was completed with over 132 documents, 37 specifically about wind turbines, summarized into a technology matrix. This matrix lists the technology, what can be monitored with this technology, and gives a short summary of the key aspects of the technology and its application. Passive and active acoustic emission equipment from Physical Acoustics Corp. and Acellent Technologies have been evaluated and selected for use in experimental state loading and fatigue tests of composite wind turbine blade materials. Acoustic Emission (AE) and Active Ultrasonic Testing (AUT), were applied to composite coupons with both simulated and actual damage. The results found that, while composites are more complicated in nature, compared to metallic structures, an artificial neural network analysis could still be used to determine damage. For the AE system, the failure mode could be determined (i.e. fiber breakage, delamination, etc.). The Acellent system has been evaluated to work well with composite materials. A test-rig for reliability testing of the rotating components was constructed. The research on the types of bearings used in the wind turbines indicated that in most of the designs, the main bearings utilized to support the shaft are cylindrical roller bearings. The accelerated degradation testing of a population of bearings was performed. Vibration and acoustic emission data was collected and analyzed in order to identify a representative degradation signal for each bearing to identify the initiation of the degradation process in the bearings. Afterwards, the RMS of the vibration signal from degradation initiation up to the end of the useful life of the bearing was selected to predict the remaining useful life of the bearing. This step included fitting Autoregressive Moving Average (ARMA) models to the degradation signals and approximating the probability distribution function (PDF) of remaining useful life

  16. Compositional, structural and morphological modifications of N-rich Cu{sub 3}N films induced by irradiation with Cu ions at 42 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Gordillo, N [Fundacion Parque CientIfico de Madrid, E-28049, Madrid (Spain); Rivera, A; Gonzalez-Arrabal, R [Instituto de Microelectronica de Madrid C/ Isaac Newton, 8. Tres Cantos, Madrid. E-28760 (Spain); Groetzschel, R; Munnik, F; Guettler, D [Forschungszentrum Dresden-Rossendorf, PO Box 10119, D-01314 Dresden (Germany); Crespillo, M L; Agullo-Lopez, F, E-mail: nuria.gordillo@uam.e [Centro de Microanalisis de Materiales, Universidad Autonoma de Madrid, E-28049, Madrid (Spain)

    2010-09-01

    N-rich Cu{sub 3}N films were irradiated with Cu at 42 MeV in the fluences range from 4 x 10{sup 11} to 1 x 10{sup 14} cm{sup -2}. The radiation-induced changes in the chemical composition, structural phases, surface morphology and optical properties have been characterized as a function of ion fluence, substrate temperature and angle of incidence of the incoming ion by means of ion-beam analysis (IBA), x-ray diffraction, atomic force microscopy, profilometry and Fourier transform infrared spectroscopy techniques. IBA methods reveal a very efficient sputtering of N whose yield (5 x 10{sup 3} atom/ion) is almost independent of substrate temperature (RT-300 {sup 0}C) but slightly depends on the incidence angle of the incoming ion. The Cu content remains essentially constant within the investigated fluence range. All data suggest an electronic mechanism to be responsible for the N depletion. The release of nitrogen and the formation of Cu{sub 2}O and metallic Cu are discussed on the basis of existing models.

  17. Modifications in morphological, structural, electrical and mechanical properties of Fe-1.0 wt.% Cu alloy on irradiation with 532 nm-6 ns Nd:YAG laser shots

    Science.gov (United States)

    Butt, M. Z.; Ur-Rehman, Khalil; Ali, Dilawar; Aftab, Muzamil; Usman Tanveer, M.

    2017-09-01

    The role of laser irradiation in tailoring the mechanical and electrical properties of Fe-1.0 wt.% Cu alloy has been explored, and compared with that of energetic particle irradiation. Mechanically polished/annealed Fe-1.0 wt.% Cu alloy specimens were irradiated in a vacuum ~10-3 Torr with 1-2500 laser shots. The laser fluence and laser intensity at the laser spot on the target surface were 86.54 J cm-2 and 14.4  ×  109 W cm-2, respectively. Different surface morphological features, e.g. dips, ripples, ridges, nanohillocks, microcones, micropillars, cavities, grooves, nano- and micro-size droplets, as well as tadpole-like structures, etc, were observed by SEM. Surface roughness was maximum for 1 laser shot, decreased by 40% for 250 laser shots, and then reduced by 70% in the range 500-2500. Crystallite size D and lattice strain ɛ were determined by Williamson-Hall analysis of x-ray diffractographs. An increasing linear relationship between electrical resistivity and Vickers hardness was found. In a plot of hardness versus D -1/2, crossover from Hall-Petch to Inverse Hall-Petch relation was observed at a critical value of D  ≈  11 nm. This behaviour was also followed by electrical resistivity. It is established that the nature of microstructural changes produced in the alloy on laser irradiation and on energetic particle irradiation is different.

  18. Structure-activity relationship studies on a Trp dendrimer with dual activities against HIV and enterovirus A71. Modifications on the amino acid.

    Science.gov (United States)

    Martínez-Gualda, Belén; Sun, Liang; Rivero-Buceta, Eva; Flores, Aida; Quesada, Ernesto; Balzarini, Jan; Noppen, Sam; Liekens, Sandra; Schols, Dominique; Neyts, Johan; Leyssen, Pieter; Mirabelli, Carmen; Camarasa, María-José; San-Félix, Ana

    2017-03-01

    We have recently described a new class of dendrimers with tryptophan (Trp) on the surface that show dual antiviral activities against HIV and EV71 enterovirus. The prototype compound of this family is a pentaerythritol derivative with 12 Trps on the periphery. Here we complete the structure-activity relationship studies of this family to identify key features that might be significant for the antiviral activity. With this aim, novel dendrimers containing different amino acids (aromatic and non-aromatic), tryptamine (a "decarboxylated" analogue of Trp) and N-methyl Trp on the periphery have been prepared. Dendrimer with N-Methyl Trp was the most active against HIV-1 and HIV-2 while dendrimer with tyrosine was endowed with the most potent antiviral activity against EV71. This tyrosine dendrimer proved to inhibit a large panel of EV71 clinical isolates (belonging to different clusters) in the low nanomolar/high picomolar range. In addition, a new synthetic procedure (convergent approach) has been developed for the synthesis of the prototype and some other dendrimers. This convergent approach proved more efficient (higher yields, easier purification) than the divergent approach previously reported. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  19. [Modification of the structure of penial glands in males of the intertidal molluscs Littorina saxatilis and L. obtusata under the influence of the infestation by trematode parthenites].

    Science.gov (United States)

    Ganzha, E V; Granovich, A I

    2008-01-01

    Sporocycts of the "pygmaeus" microphallides (Microphallus piriformes) are localized in hepatopancreas and gonads of Littorina molluscs causing total parasitic castration. A histological study of penial glands in Littorina saxatilis and L. obtusata males infested with trematodes M. piriformes has been made. Copulatory organs of noninfested molluscs, molluscs after recent contamination (with not completely formed daughter sporocysts), and molluscs containing mature metacercariae inside daughter sporocysts were examined. Based on the data obtained, probable dynamics of the histological structure of infested glandular apparatus was established. It was shown, that the trematode infestation have an influence on the muscular and secretory parts of penial glands. The wall of the penial gland muscular capsule becomes more fine in infested L. saxatilis. On the contrary, this wall is vastly thicker in infested L. obtusata, as compared with noninfested individuals. Glandular cells of the molluscs' penial glands decreases the amount of granular secret in both species. In L. obtusata the number of secretory cells is shown to be reduced up to their total disappearance. The above pathological changes probably prevent normal function of penial glands.

  20. Study of electronic structure modifications of silicon oxides (alpha SiO2), aluminium oxide (alpha Al2O3) and yttrium oxide (Y2O3) induced by structure defects (non stoichiometry, stresses, high energy ion irradiation)

    International Nuclear Information System (INIS)

    Jollet, F.

    1989-10-01

    Influence of structure defects on electronic structure of ceramics is studied by X-ray absorption spectroscopy, photoelectron spectroscopy and state density calculations with the tight-binding model. Are investigated: Influence of oxygen stoichiometry on electronic structure of yttrium oxide, effect of mechanical stress on electronic structure of quartz alpha and effect of irradiation by high energy ions on electronic structure of quartz. Irradiated quartz show a disorganized crystalline state which is different from amorphous state. Results are interpreted as metamicte state internal stresses [fr

  1. Modification of Experimental Protocols for a Space Shuttle Flight and Applications for the Analysis of Cytoskeletal Structures During Fertilization, Cell Division , and Development in Sea Urchin Embryos

    Science.gov (United States)

    Chakrabarti, Amitabha; Stoecker, Andrew; Schatten, Heide

    1995-01-01

    To explore the role of microgravity on cytoskeletal organization and skeletal calcium deposition during fertilization, cell division, and early development, the sea urchin was chosen as a model developmental system. Methods were developed to employ light, immunofluorescence, and electron microscopy on cultures being prepared for flight on the Space Shuttle. For analysis of microfilaments, microtubules, centrosomes, and calcium-requiring events, our standard laboratory protocols had to be modified substantially for experimentation on the Space Shuttle. All manipulations were carried out in a closed culture chamber containing 35 ml artificial sea water as a culture fluid. Unfertilized eggs stored for 24 hours in these chambers were fertilized with sperm diluted in sea water and fixed with concentrated fixatives for final fixation in formaldehyde, taxol, EGTA, and MgCl2(exp -6)H2O for 1 cell to 16 cell stages to preserve cytoskeletal structures for simultaneous analysis with light, immunofluorescence, and electron microscopy, and 1.5 percent glutaraldehyde and 0.4 percent formaldehyde for blastula and plueus stages. The fixed samples wre maintained in chambers without degradation for up to two weeks after which the specimens were processed and analyzed with routine methods. Since complex manipulations are not possible in the closed chambers, the fertilization coat was removed from fixation using 0.5 percent freshly prepared sodium thioglycolate solution at pH 10.0 which provided reliable immunofluorescence staining for microtubules. Sperm/egg fusion, mitosis, cytokinesis, and calcium deposition during spicule formatin in early embryogenesis were found to be without artificial alterations when compared to cells fixed fresh and processed with conventional methods.

  2. Differential Effects of Structural Modifications on the Competition of Chalcones for the PIB Amyloid Imaging Ligand-Binding Site in Alzheimer's Disease Brain and Synthetic Aβ Fibrils.

    Science.gov (United States)

    Fosso, Marina Y; McCarty, Katie; Head, Elizabeth; Garneau-Tsodikova, Sylvie; LeVine, Harry

    2016-02-17

    Alzheimer's disease (AD) is a complex brain disorder that still remains ill defined. In order to understand the significance of binding of different clinical in vivo imaging ligands to the polymorphic pathological features of AD brain, the molecular characteristics of the ligand interacting with its specific binding site need to be defined. Herein, we observed that tritiated Pittsburgh Compound B ((3)H-PIB) can be displaced from synthetic Aβ(1-40) and Aβ(1-42) fibrils and from the PIB binding complex purified from human AD brain (ADPBC) by molecules containing a chalcone structural scaffold. We evaluated how substitution on the chalcone scaffold alters its ability to displace (3)H-PIB from the synthetic fibrils and ADPBC. By comparing unsubstituted core chalcone scaffolds along with the effects of bromine and methyl substitution at various positions, we found that attaching a hydroxyl group on the ring adjacent to the carbonyl group (ring I) of the parent member of the chalcone family generally improved the binding affinity of chalcones toward ADPBC and synthetic fibrils F40 and F42. Furthermore, any substitution on ring I at the ortho-position of the carbonyl group greatly decreases the binding affinity of the chalcones, potentially as a result of steric hindrance. Together with the finding that neither our chalcones nor PIB interact with the Congo Red/X-34 binding site, these molecules provide new tools to selectively probe the PIB binding site that is found in human AD brain, but not in brains of AD pathology animal models. Our chalcone derivatives also provide important information on the effects of fibril polymorphism on ligand binding.

  3. Structural and optical properties of DC magnetron sputtered ZnO films on glass substrate and their modification by Ag ions implantation

    Science.gov (United States)

    Ahmad, R.; Afzal, Naveed; Amjad, U.; Jabbar, S.; Hussain, T.; Hussnain, A.

    2017-07-01

    This work is focused on investigating the effects of deposition time and Ag ions implantation on structural and optical properties of ZnO film. The ZnO film was prepared on glass substrate by pulsed DC magnetron sputtering of pure Zn target in reactive oxygen environment for 2 h, 3 h, 4 h and 5 h respectively. X-ray diffraction results revealed polycrystalline ZnO film whose crystallinity was improved with increase of the deposition time. The morphological features indicated agglomeration of smaller grains into larger ones by increasing the deposition time. The UV-vis spectroscopy analysis depicted a small decrease in the band gap of ZnO from 3.36 eV to 3.27 eV with increase of deposition time. The Ag ions implantation in ZnO films deposited for 5 h on glass was carried out by using Pelletron Accelerator at different ions fluences ranging from 1  ×  1011 ions cm-2 to 2  ×  1012 ions cm-2. XRD patterns of Ag ions implanted ZnO did not show significant change in crystallite size by increasing ions fluence from 1  ×  1011 ions cm-2 to 5  ×  1011 ions cm-2. However, with further increase of the ions fluence, the crystallite size was decreased. The band gap of Ag ions implanted ZnO indicated anomalous variations with increase of the ions fluence.

  4. Multicharged Ion-induced simple molecule fragmentation dynamics; Dynamique de la fragmentation de molecules simples induite par impact d'ion multicharge

    Energy Technology Data Exchange (ETDEWEB)

    Tarisien, M

    2003-10-01

    The aim of this work is to study the dynamics of swift multicharged ion-induced fragmentation of diatomic (CO) and triatomic (CO{sub 2}) molecules. Performed at the GANIL facility, this study used the Recoil Ion Momentum Spectroscopy technique (RIMS), which consists of a time-of-flight mass spectrometer, coupled with a multi-hit capability position sensitive detector (delay line anode). The high-resolution measurement of the kinetic energy distribution released (KER) during the CO fragmentation points out the limitation of the Coulomb Explosion Model, revealing, for example, the di-cation CO{sub 2}{sup +} electronic state contribution in the case of C{sup +}/O{sup +} fragmentation pathway. Furthermore, the multi-ionization cross section dependence with the orientation of the internuclear axis of CO is compared with a geometrical model calculation. Finally, different behaviours are observed for the dissociation dynamics of a triatomic molecule (CO{sub 2}). While triple ionization leads mainly to a synchronous concerted fragmentation dynamics, a weak fraction of dissociating molecule follows a sequential dynamics involving CO{sub 2}{sup +} metastable states. In the case of double ionization, (CO{sub 2}){sup 2+} di-cation dissociation dynamics is asynchronously concerted and has been interpreted using a simple model involving an asymmetrical vibration of the molecule. (author)

  5. Angle-differential observation of plasmon electrons in the double-differential cross-section spectra of fast-ion-induced electron ejection from C60

    Science.gov (United States)

    Kelkar, A. H.; Gulyás, L.; Tribedi, Lokesh C.

    2015-11-01

    We report on the measurement of double-differential distribution of soft electron emission from C60 fullerene, induced by a fast-moving Coulomb field of 76 MeV energy bare fluorine ions. A broad "plasmon-electron" peak, riding on the Coulomb-ionization continuum, is observed due to the deexcitation of the giant dipole plasmon resonance state in C60. The angular distribution of the plasmon electrons goes through a dip around 90°, which is contrary to that observed in ion-atom collisions measured in situ, indicating the alignment of the induced dipole moment along the projectile beam direction. A model based on the photoelectron angular distribution which is modified due to the ion-induced postcollisional interaction provides an excellent agreement with the observed asymmetric distribution. The distribution smoothly changes from a dip at 90° to a peak with the variation of ejected electron energy indicating transition from a collective plasmon behavior of the whole system to a single ion-atom interaction. The single-differential cross section was also derived, which preserves the signature of the collective excitation.

  6. Mean carrier transport properties and charge collection dynamics of single-crystal, natural type IIa diamonds from ion-induced conductivity measurements

    Energy Technology Data Exchange (ETDEWEB)

    Han, Sung Su [Univ. of California, Berkeley, CA (United States)

    1993-09-01

    Ion-induced conductivity has been used to investigate the detector characteristics of diamond detectors. Both integrated-charge, and time-resolved current measurements were performed to examine the mean carrier transport properties of diamond and the dynamics of charge collection under highly-localized and high-density excitation conditions. The integrated-charge measurements were conducted with a standard pulse-counting system with 241Am radioactivity as the excitation source for the detectors. The time-resolved current measurements were performed using a 70 GHz random sampling oscilloscope with the detectors incorporated into high-speed microstrip transmission lines and the excitation source for these measurements was an ion beam of either 5-MeV He+ or 10-MeV Si3+. The detectors used in both experiments can be described as metal-semiconductor-metal (MSM) devices where a volume of the detector material is sandwiched between two metal plates. A charge collection model was developed to interpret the integrated-charge measurements which enabled estimation of the energy required to produce an electron-hole pair (ϵdi) and the mean carrier transport properties in diamond, such as carrier mobility and lifetime, and the behavior of the electrical contacts to diamond.

  7. Structural differences between the avian and human H7N9 hemagglutinin proteins are attributable to modifications in salt bridge formation: a computational study with implications in viral evolution.

    Directory of Open Access Journals (Sweden)

    Marni E Cueno

    Full Text Available Influenza A hemagglutinin (HA is a homotrimeric glycoprotein composed of a fibrous globular stem supporting a globular head containing three sialic acid binding sites responsible for infection. The H7N9 strain has consistently infected an avian host, however, the novel 2013 strain is now capable of infecting a human host which would imply that the HA in both strains structurally differ. A better understanding of the structural differences between the avian and human H7N9 strains may shed light into viral evolution and transmissibility. In this study, we elucidated the structural differences between the avian and human H7N9 strains. Throughout the study, we generated HA homology models, verified the quality of each model, superimposed HA homology models to determine structural differences, and, likewise, elucidated the probable cause for these structural differences. We detected two different types of structural differences between the novel H7N9 human and representative avian strains, wherein, one type (Pattern-1 showed three non-overlapping regions while the other type (Pattern-2 showed only one non-overlapping region. In addition, we found that superimposed HA homology models exhibiting Pattern-1 contain three non-overlapping regions designated as: Region-1 (S1571-A1601; Region-3 (R2621-S2651; and Region-4 (S2701-D2811, whereas, superimposed HA homology models showing Pattern-2 only contain one non-overlapping region designated as Region-2 (S1371-S1451. We attributed the two patterns we observed to either the presence of salt bridges involving the E1141 residue or absence of the R1411:D771 salt bridge. Interestingly, comparison between the human H7N7 and H7N9 HA homology models showed high structural similarity. We propose that the putative absence of the R1411:D771 salt bridge coupled with the putative presence of the E1141:R2621 and E1141:K2641 salt bridges found in the 2013 H7N9 HA homology model is associated to human-type receptor binding

  8. Epigenetic modifications and diabetic nephropathy

    Directory of Open Access Journals (Sweden)

    Marpadga A. Reddy

    2012-09-01

    Full Text Available Diabetic nephropathy (DN is a major complication associated with both type 1 and type 2 diabetes, and a leading cause of end-stage renal disease. Conventional therapeutic strategies are not fully efficacious in the treatment of DN, suggesting an incomplete understanding of the gene regulation mechanisms involved in its pathogenesis. Furthermore, evidence from clinical trials has demonstrated a “metabolic memory” of prior exposure to hyperglycemia that continues to persist despite subsequent glycemic control. This remains a major challenge in the treatment of DN and other vascular complications. Epigenetic mechanisms such as DNA methylation, nucleosomal histone modifications, and noncoding RNAs control gene expression through regulation of chromatin structure and function and post-transcriptional mechanisms without altering the underlying DNA sequence. Emerging evidence indicates that multiple factors involved in the etiology of diabetes can alter epigenetic mechanisms and regulate the susceptibility to diabetes complications. Recent studies have demonstrated the involvement of histone lysine methylation in the regulation of key fibrotic and inflammatory genes related to diabetes complications including DN. Interestingly, histone lysine methylation persisted in vascular cells even after withdrawal from the diabetic milieu, demonstrating a potential role of epigenetic modifications in metabolic memory. Rapid advances in high-throughput technologies in the fields of genomics and epigenomics can lead to the identification of genome-wide alterations in key epigenetic modifications in vascular and renal cells in diabetes. Altogether, these findings can lead to the identification of potential predictive biomarkers and development of novel epigenetic therapies for diabetes and its associated complications.

  9. Hydrogen and copper ion induced molecular reorganizations in two new scorpiand-like ligands appended with pyridine rings.

    Science.gov (United States)

    Blasco, Salvador; Verdejo, Begoña; Clares, M Paz; Castillo, Carmen E; Algarra, Andrés G; Latorre, Julio; Máñez, M Angeles; Basallote, Manuel G; Soriano, Conxa; García-España, Enrique

    2010-08-02

    The synthesis of two new ligands constituted of a tris(2-aminoethyl)amine moiety linked to the 2,6 positions of a pyridine spacer through methylene groups in which the hanging arm is further functionalized with a 2-pycolyl (L1) or 3-pycolyl (L2) group is presented. The protonation of L1 and L2 and formation of Cu(2+) complexes have been studied using potentiometric, NMR, X-ray, and kinetic experiments. The results provide new information about the relevance of molecular movements in the chemistry of this kind of so-called scorpiand ligand. The comparison between these two ligands that only differ in the position of the substituent at the arm reveals important differences in both thermodynamic and kinetic properties. The Cu(2+) complex with L1 is several orders of magnitude more stable than that with L2, surely because in the latter case the pyridine nitrogen at the pendant arm is unable to coordinate to the metal ion with the ligand acting as hexadentate, a possibility that occurs in the case of [CuL1](2+), as demonstrated by its crystal structure. Significant differences are also found between both ligands in the kinetic studies of complex formation and decomposition. For L1, those processes occur in a single kinetic step, whereas for L2 they occur with the formation of a detectable reaction intermediate whose structure corresponds to that resulting from the movement typical of scorpiands. Another interesting conclusion derived from kinetic studies on complex formation is that the reactive form of the ligand is H(3)L(3+) for L1 and H(2)L(2+) for L2. DFT calculations are also reported, and they allow a rationalization of the kinetic results relative to the reactive forms of the ligands in the process of complex formation. In addition, they provide a full picture of the mechanistic pathway leading to the formation of the first Cu-N bond, including outer-sphere complexation, water dissociation, and reorganization of the outer-sphere complex.

  10. Enzymatic modification of starch

    DEFF Research Database (Denmark)

    Jensen, Susanne Langgård

    In the food industry approaches for using bioengineering are investigated as alternatives to conventional chemical and physical starch modification techniques in development of starches with specific properties. Enzyme-assisted post-harvest modification is an interesting approach to this, since...... it is considered a clean and energy saving technology. This thesis aimed to investigate the effect of using reaction conditions, simulating an industrial process, for enzymatic treatment of starch with branching enzyme (BE) from Rhodothermus obamensis. Thus treatements were conducted at 70°C using very high...... substrate concentration (30-40% dry matter (DM)) and high enzyme activity (750-2250 BE units (BEU)/g sample). Starches from various botanical sources, representing a broad range of properties, were used as substrates. The effects of the used conditions on the BE-reaction were evaluated by characterization...

  11. Geometrically Consistent Mesh Modification

    KAUST Repository

    Bonito, A.

    2010-01-01

    A new paradigm of adaptivity is to execute refinement, coarsening, and smoothing of meshes on manifolds with incomplete information about their geometry and yet preserve position and curvature accuracy. We refer to this collectively as geometrically consistent (GC) mesh modification. We discuss the concept of discrete GC, show the failure of naive approaches, and propose and analyze a simple algorithm that is GC and accuracy preserving. © 2010 Society for Industrial and Applied Mathematics.

  12. In-Situ Catalytic Surface Modification of Micro-Structured La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF Oxygen Permeable Membrane Using Vacuum-Assisted technique

    Directory of Open Access Journals (Sweden)

    Othman Nur Hidayati

    2016-01-01

    Full Text Available This paper aims at investigating the means to carry out in-situ surface modification of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF oxygen permeable membrane by using vacuum assisted technique. The unique structure of the LSCF hollow fibre membrane used in this study, which consists of an outer dense oxygen separation layer and conical-shaped microchannels open at the inner surface has allowed the membrane to be used as oxygen separation membrane and as a structured substrate for where catalyst can be deposited. A catalyst solution of similar material, LSCF was prepared using sol-gel technique. Effects of calcination temperature and heating rate were investigated using XRD and TGA to ensure pure perovskites structure of LSCF was obtained. It was found that a lower calcination temperature can be used to obtain pure perovskite phase if slower heating rate is used. The SEM photograph shows that the distribution of catalyst onto the membrane microchannels using in-situ deposition technique was strongly related to the viscosity of LSCF catalytic sol. Interestingly, it was found that the amount of catalyst deposited using viscous solution was slightly higher than the less viscous sol. This might be due to the difficulty of catalyst sol to infiltrate the membrane and as a result, thicker catalyst layer was observed at the lumen rather than onto the conical-shaped microchannels. Therefore, the viscosity of catalyst solution and calcination process should be precisely controlled to ensure homogeneous catalyst layer deposition. Analysis of the elemental composition will be studied in the future using energy dispersive X-ray Spectroscopy (EDX to determine the elements deposited onto the membranes. Once the elemental analysis is confirmed, oxygen permeation analysis will be carried out.

  13. Histone modifications in response to DNA damage

    International Nuclear Information System (INIS)

    Altaf, Mohammed; Saksouk, Nehme; Cote, Jacques

    2007-01-01

    The packaging of the eukaryotic genome into highly condensed chromatin makes it inaccessible to the factors required for gene transcription, DNA replication, recombination and repair. Eukaryotes have developed intricate mechanisms to overcome this repressive barrier imposed by chromatin. Histone modifying enzymes and ATP-dependent chromatin remodeling complexes play key roles here as they regulate many nuclear processes by altering the chromatin structure. Significantly, these activities are integral to the process of DNA repair where histone modifications act as signals and landing platforms for various repair proteins. This review summarizes the recent developments in our understanding of histone modifications and their role in the maintenance of genome integrity

  14. Behavior Modification in the Classroom

    Science.gov (United States)

    Whitman, Mryon; Whitman, Joan

    1971-01-01

    This article presents the theoretical rationale for behavior modification, principally through its comparison with traditional psychotherapies, and suggests some behavior modification techniques for the classroom management of maladaptive behavior. (Author)

  15. Manufacturing technologies for photovoltaics and possible means of their development in Russia (Review): Part 2. Modification of production technologies for photoelectric converters, development of contact structures, and choice of promising technologies for expansion of FEC production in Russia

    Science.gov (United States)

    Tarasenko, A. B.; Popel', O. S.

    2015-12-01

    As the development of the first part of the review of modern industrial technologies for manufacture of photoelectric converters (PECs) of solar power, the present paper considers modifications of technologies for manufacture of PECs, including various thin-film techniques. Main tendencies in the advancement of contact structures of PECs are described. Formulation and substantiation are made for promising, in the authors' opinion, lines of the development of industry of PECs in Russia based on the upcoming implementation of 1.5 GW network photovoltaic power plants to 2020, which are developed with the national support under conditions of the fulfillment of rigid requirements to manufacture localization. As the most prospective technology for development of the competitive manufacture of photoelectric converters subject to the Russian scientific and engineering groundwork, the authors recommend the technology based on single-crystal silicon of the n type with the passivation of the frontal and rear sides and symmetrical contacts ( n-PASHa), which provides the possibility to produce double-faced solar modules also.

  16. Unrestricted Mass Spectrometric Data Analysis for Identification, Localization, and Quantification of Oxidative Protein Modifications

    DEFF Research Database (Denmark)

    Rykær, Martin; Svensson, Birte; Davies, Michael J

    2017-01-01

    Oxidation generates multiple diverse post-translational modifications resulting in changes in protein structure and function associated with a wide range of diseases. Of these modifications, carbonylations have often been used as hallmarks of oxidative damage. However, accumulating evidence suppo...

  17. Structural dynamic modification using additive damping

    Indian Academy of Sciences (India)

    A viscoelastic material like polyvinyl chloride (PVC) has the characteristics of both elastic and viscous elements. The dynamic properties of such materials are represented under harmonic vibration conditions by complex moduli. This is due to the phase difference between stress ' and strain or 'a И E1 З iE2 for direct strain.

  18. Structural dynamic modification using additive damping

    Indian Academy of Sciences (India)

    B C NAKRA. Mechanical Engineering Department, Indian Institute of Technology, New. Delhi, India ... design as in flow systems, avoiding resonances by change in mass and/or stiffness, use of vibration absorbers and ... The objective of the present paper is to discuss some of the above topics. Detailed reviews on the ...

  19. Structural modification of a steam turbine blade

    Science.gov (United States)

    Heidari, M.; Amini, K.

    2017-05-01

    Blades are significant components of steam turbines which are failed due to stresses arising from centrifugal and bending forces. The turbine blade has a number of geometrical variables that need to be considered at the design stage. Hence, this paper investigated a three-dimensional model of steam turbine blade with different lengths and thicknesses using finite element method. A three-dimensional model of blade was developed using a computer-aided design software. All materials were assumed linear, homogenous, elastic and isotropic. A 5 N widespread force was applied to the blade. The results of this study showed that longer blades are experienced higher maximum Von Mises stress and strain than shorter ones. The blade with the length of 400 mm and thickness of 20 mm experienced the lowest maximum Von Mises stress at 51 kPa. Furthermore, blade with the length of 400 mm and 600 mm experienced the lowest and highest strain at 3.07 × 10-6 and 4.3 × 10-6 respectively. In addition, thicker blades were undergone less maximum Von Mises stress and strain than thinner ones. Understanding stress and strain pattern in turbine blades provides useful knowledge which can be useful to estimate the fatigue in turbine blades.

  20. Induction of helical structure in a heptapeptide with a metal cross-link: modification of the Lifson-Roig helix-coil theory to account for covalent cross-links.

    Science.gov (United States)

    Kise, Kenneth J; Bowler, Bruce E

    2002-12-31

    A short peptide, acetyl-AHAAAHA-carboxamide, has been synthesized and the histidines cross-linked with a cis-tetraammineruthenium(III) moiety. In the absence of the Ru(III) cross-link, the heptapeptide is essentially structureless, as judged by circular dichroism, NMR chemical shift, and NMR-monitored hydrogen deuterium exchange data. The presence of the cis-Ru(III) cross-link is confirmed by mass spectral data and the characteristic pH dependence of the UV-vis spectrum of the cis-(bis-(imidazole))ruthenium(III) unit. Circular dichroism data indicate that the Ru(III) cross-linked heptapeptide is approximately 37% helical at 0 degrees C. The NMR spectrum of the cross-linked peptide has been fully assigned using TOCSY and ROESY experiments. ROE interactions and J-coupling data provide evidence for helical structure. NMR-monitored hydrogen-deuterium exchange data for the Ru(III)-cross-linked peptide, resolved at the level of the individual amides, give larger protection factors at the ends than in the center of the helix. Steric and polarization effects of the Ru(III) cross-link are proposed to cause this unusual apparent protection pattern. A modification to the Lifson-Roig helix-coil model to account for the effect of the i,i+4 Ru(III) cross-link on the helix-coil transition of a peptide is presented. The model provides an excellent fit to the temperature dependence of the circular dichroism spectrum of the Ru(III)-cross-linked peptide. The modified model indicates that the effect of the cross-link on the nucleation parameter, v(2), is modest (about 7-fold) for residues bounded by the cross-link. Significant increases in the propagation parameter, w, occur for residues within the cross-link. The modification to the Lifson-Roig model accounts for the effect of a Ru(III) cross-link on the circular dichroism spectrum of a previously reported 17 residue peptide.