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Sample records for particle-induced amorphization complex

  1. Particle-induced amorphization of complex ceramics. Final report

    SciTech Connect

    Ewing, R.C.; Wang, L.M.

    1998-08-01

    The crystalline-to-amorphous (c-a) phase transition is of fundamental importance. Particle irradiations provide an important, highly controlled means of investigating this phase transformation and the structure of the amorphous state. The interaction of heavy-particles with ceramics is complex because these materials have a wide range of structure types, complex compositions, and because chemical bonding is variable. Radiation damage and annealing can produce diverse results, but most commonly, single crystals become aperiodic or break down into a polycrystalline aggregate. The authors continued the studies of the transition from the periodic-to-aperiodic state in natural materials that have been damaged by {alpha}-recoil nuclei in the uranium and thorium decay series and in synthetic, analogous structures. The transition from the periodic to aperiodic state was followed by detailed x-ray diffraction analysis, in-situ irradiation/transmission electron microscopy, high resolution transmission electron microscopy, extended x-ray absorption fine structure spectroscopy/x-ray absorption near edge spectroscopy and other spectroscopic techniques. These studies were completed in conjunction with bulk irradiations that can be completed at Los Alamos National Laboratory or Sandia National Laboratories. Principal questions addressed in this research program included: (1) What is the process at the atomic level by which a ceramic material is transformed into a disordered or aperiodic state? (2) What are the controlling effects of structural topology, bond-type, dose rate, and irradiation temperature on the final state of the irradiated material? (3) What is the structure of the damaged material? (4) What are the mechanisms and kinetics for the annealing of interstitial and aggregate defects in these irradiated ceramic materials? (5) What general criteria may be applied to the prediction of amorphization in complex ceramics?

  2. Amorphic complexity

    NASA Astrophysics Data System (ADS)

    Fuhrmann, G.; Gröger, M.; Jäger, T.

    2016-02-01

    We introduce amorphic complexity as a new topological invariant that measures the complexity of dynamical systems in the regime of zero entropy. Its main purpose is to detect the very onset of disorder in the asymptotic behaviour. For instance, it gives positive value to Denjoy examples on the circle and Sturmian subshifts, while being zero for all isometries and Morse-Smale systems. After discussing basic properties and examples, we show that amorphic complexity and the underlying asymptotic separation numbers can be used to distinguish almost automorphic minimal systems from equicontinuous ones. For symbolic systems, amorphic complexity equals the box dimension of the associated Besicovitch space. In this context, we concentrate on regular Toeplitz flows and give a detailed description of the relation to the scaling behaviour of the densities of the p-skeletons. Finally, we take a look at strange non-chaotic attractors appearing in so-called pinched skew product systems. Continuous-time systems, more general group actions and the application to cut and project quasicrystals will be treated in subsequent work.

  3. Particle-induced amorphization complex ceramic

    SciTech Connect

    Ewing, R.C.; Wang, Lu-Min

    1996-02-16

    The presently funded three-year research program, supported by the Division of Materials Sciences of the Office of Basic Energy Sciences, was initiated on August 1, 1993; during the period in which the grant will have been active, $249,561 of support have been provided to date with an additional $79,723 to be spent during the third, final year (ending July 30, 1996). The primary purpose of the program is to develop an understanding of heavy-particle radiation effects -- {alpha}-recoil nuclei, fission fragments, ion-irradiations -- on ceramic materials and the thermal annealing mechanisms by which crystallinity might be restored. During the past two years, we have completed major studies on zircon (ZrSiO{sub 4}), olivine (Mg{sub 2}SiO{sub 4} and ten other compositions), spinel (MgAl{sub 2}O{sub 4} and four other compositions), and silica polymorphs (quartz, coesite and stishovite), as well as berlinite (AlPO{sub 4}) which is isomorphous with quartz. In addition, based on the above research, we propose the use of zircon as a host phase for the immobilization of plutonium resulting from weapons dismantlement.

  4. Force-field parameters for beryllium complexes in amorphous layers.

    PubMed

    Emelyanova, Svetlana; Chashchikhin, Vladimir; Bagaturyants, Alexander

    2016-09-01

    Unknown force-field parameters for metal organic beryllium complexes used in emitting and electron transporting layers of OLED structures are determined. These parameters can be used for the predictive atomistic simulations of the structure and properties of amorphous organic layers containing beryllium complexes. The parameters are found for the AMBER force field using a relaxed scan procedure and quantum-mechanical DFT calculations of potential energy curves for specific internal (angular) coordinates in a series of three Be complexes (Bebq2; Be(4-mpp)2; Bepp2). The obtained parameters are verified in calculations of some molecular and crystal structures available from either quantum-mechanical DFT calculations or experimental data. Graphical Abstract Beryllium complexes in amorphous layersᅟ.

  5. Impurity-defect complexes in hydrogenated amorphous silicon

    SciTech Connect

    Yang, L.H. ); Fong, C.Y. . Dept. of Physics); Nichols, C.S. . Dept. of Materials Science and Engineering)

    1990-11-01

    The two most outstanding features observed for dopants in hydrogenated amorphous silicon (a-Si:H) -- a shift in the Fermi level accompanied by an increase in the defect density and an absence of degenerate doping -- have previously been postulated to stem from the formation of substitutional dopant-dangling bond complexes. Using first-principles self-consistent pseudopotential calculation in conjunction with a supercell model for the amorphous network and the ability of network relaxation from the first-principles results, we have studied the electronic and structural properties of substitutional fourfold-coordinated phosphorus and boron at the second neighbor position to a dangling bond defect. We demonstrate that such impurity-defect complexes can account for the general features observed experimentally in doped a-Si:H. 16 refs., 2 figs., 1 tab.

  6. Amorphization of complex ceramics by heavy-particle irradiations

    SciTech Connect

    Ewing, R.C.; Wang, L.M.; Weber, W.J.

    1994-11-01

    Complex ceramics, for the purpose of this paper, include materials that are generally strongly bonded (mixed ionic and covalent), refractory and frequently good insulators. They are distinguished from simple, compact ceramics (e.g., MgO and UO{sub 2}) by structural features which include: (1) open network structures, best characterized by a consideration of the shape, size and connectivity of coordination polyhedra; (2) complex compositions which characteristically lead to multiple cation sites and lower symmetry; (3) directional bonding; (4) bond-type variations within the structure. The heavy particle irradiations include ion-beam irradiations and recoil-nucleus damage resulting from a-decay events from constituent actinides. The latter effects are responsible for the radiation-induced transformation to the metamict state in minerals. The responses of these materials to irradiation are complex, as energy may be dissipated ballistically by transfer of kinetic energy from an incident projectile or radiolytically by conversion of radiation-induced electronic excitations into atomic motion. This results in isolated Frenkel defect pairs, defect aggregates, isolated collision cascades or bulk amorphization. Thus, the amorphization process is heterogeneous. Only recently have there been systematic studies of heavy particle irradiations of complex ceramics on a wide variety of structure-types and compositions as a function of dose and temperature. In this paper, we review the conditions for amorphization for the tetragonal orthosilicate, zircon [ZrSiO{sub 4}]; the hexagonal orthosilicate/phosphate apatite structure-type [X{sub 10}(ZO{sub 4}){sub 6}(F,Cl,O){sub 2}]; the isometric pyrochlores [A{sub 1-2}B{sub 2}O{sub 6}(O,OH,F){sub 0-1p}H{sub 2}O] and its monoclinic derivative zirconotite [CaZrTi{sub 2}O{sub 7}]; the olivine (derivative - hcp) structure types, {alpha}-{sup VI}A{sub 2}{sup IV}BO{sub 4}, and spinel (ccp), {gamma}-{sup VI}A{sub 2}{sup IV}BO{sub 4}.

  7. Unveiling the complex electronic structure of amorphous metal oxides

    PubMed Central

    Århammar, C.; Pietzsch, Annette; Bock, Nicolas; Holmström, Erik; Araujo, C. Moyses; Gråsjö, Johan; Zhao, Shuxi; Green, Sara; Peery, T.; Hennies, Franz; Amerioun, Shahrad; Föhlisch, Alexander; Schlappa, Justine; Schmitt, Thorsten; Strocov, Vladimir N.; Niklasson, Gunnar A.; Wallace, Duane C.; Rubensson, Jan-Erik; Johansson, Börje; Ahuja, Rajeev

    2011-01-01

    Amorphous materials represent a large and important emerging area of material’s science. Amorphous oxides are key technological oxides in applications such as a gate dielectric in Complementary metal-oxide semiconductor devices and in Silicon-Oxide-Nitride-Oxide-Silicon and TANOS (TaN-Al2O3-Si3N4-SiO2-Silicon) flash memories. These technologies are required for the high packing density of today’s integrated circuits. Therefore the investigation of defect states in these structures is crucial. In this work we present X-ray synchrotron measurements, with an energy resolution which is about 5–10 times higher than is attainable with standard spectrometers, of amorphous alumina. We demonstrate that our experimental results are in agreement with calculated spectra of amorphous alumina which we have generated by stochastic quenching. This first principles method, which we have recently developed, is found to be superior to molecular dynamics in simulating the rapid gas to solid transition that takes place as this material is deposited for thin film applications. We detect and analyze in detail states in the band gap that originate from oxygen pairs. Similar states were previously found in amorphous alumina by other spectroscopic methods and were assigned to oxygen vacancies claimed to act mutually as electron and hole traps. The oxygen pairs which we probe in this work act as hole traps only and will influence the information retention in electronic devices. In amorphous silica oxygen pairs have already been found, thus they may be a feature which is characteristic also of other amorphous metal oxides.

  8. Iridium Complexes and Clusters in Dealuminated Zeolite HY: Distribution between Crystalline and Impurity Amorphous Regions

    SciTech Connect

    Martinez-Macias, Claudia; Xu, Pinghong; Hwang, Son-Jong; Lu, Jing; Chen, Cong-Yan; Browning, Nigel D.; Gates, Bruce C.

    2014-07-08

    Dealuminated zeolite HY was used to support Ir(CO)2 complexes formed from Ir(CO)2(C5H7O2). Infrared and X-ray absorption spectra and atomic-resolution electron microscopy images identify these complexes, and the images and 27Al NMR spectra identify impurity amorphous regions in the zeolite where the iridium is more susceptible to aggregation than in the crystalline regions. The results indicate a significant stability limitation of metal in amorphous impurity regions of zeolites.

  9. Circular dichroism spectroscopy study of crystalline-to-amorphous transformation in chiral platinum(II) complexes.

    PubMed

    Zhang, Xiao-Peng; Wu, Tao; Liu, Jian; Zhao, Jin-Cheng; Li, Cheng-Hui; You, Xiao-Zeng

    2013-07-01

    Two couples of enantiomeric platinum(II) complexes: Pt(L1a )Cl (1a), Pt(L1b )Cl (1b) and Pt(L1a )(C ≡ C - Ph) (2a), Pt(L1b )(C ≡ C - Ph) (2b) (L1a  = (+)-1,3-di-(2-(4,5-pinene)pyridyl)benzene, L1b  = (-)-1,3-di-(2-(4,5-pinene)pyridyl)benzene) were synthesized and characterized. Their absolute configurations were determined by single crystal X-ray diffraction and further verified by circular dichroism (CD) spectra (including electronic circular dichroism [ECD] and vibrational circular dichroism [VCD]). These complexes show interesting mechanoluminescence and/or vapoluminescence due to crystalline-to-amorphous transformation. The crystalline solids, grinding-induced amorphous powders, and vapor-induced amorphous powders of complexes 2a and 2b were comparatively investigated by solid-state ECD and VCD spectra. The transformation from crystalline solids to amorphous powders was accompanied by significant variances of the spectral feature in both ECD and VCD spectra. © 2013 Wiley Periodicals, Inc.

  10. Self-assembled amorphous drug-polyelectrolyte nanoparticle complex with enhanced dissolution rate and saturation solubility.

    PubMed

    Cheow, Wean Sin; Hadinoto, Kunn

    2012-02-01

    The dissolution rate and solubility of poorly soluble drugs can be enhanced by formulating them into stable amorphous nanoparticle complex (nanoplex). For this purpose, a highly sustainable self-assembly drug-polyelectrolyte complexation process is developed, with ciprofloxacin and dextran sulfate as the drug and polyelectrolyte models, respectively. The nanoplex are prepared by mixing two aqueous salt solutions - one containing the drug and the other containing the oppositely charged polyelectrolyte. The nanoplex suspension is transformed into stable dry-powder form by freeze-drying. The effects of drug concentration, drug-to-polyelectrolyte charge ratio, and salt concentration on the complexation efficiency, yield, drug loading, and nanoplex morphology are examined. The dissolution rates and solubility of the nanoplex are characterized and compared to raw drug crystals. Nearly spherical amorphous nanoplex having fairly uniform sizes in the range of 200-400 nm and 80% drug loading are successfully produced at ≥80% complexation efficiency and yield. The complexation efficiency is governed by the drug concentration and its ratio to the salt concentration. The nanoplex powders exhibit approximately twice higher dissolution rate and solubility than raw drug crystals and remain stable after one-month storage. Overall, amorphous nanoplex represent a promising bioavailability-enhanced formulation of poorly soluble drugs owed to their superior characteristics and ease of preparation. Copyright © 2011 Elsevier Inc. All rights reserved.

  11. Surface complexation model for strontium sorption to amorphous silica and goethite.

    PubMed

    Carroll, Susan A; Roberts, Sarah K; Criscenti, Louise J; O'Day, Peggy A

    2008-01-18

    Strontium sorption to amorphous silica and goethite was measured as a function of pH and dissolved strontium and carbonate concentrations at 25 degrees C. Strontium sorption gradually increases from 0 to 100% from pH 6 to 10 for both phases and requires multiple outer-sphere surface complexes to fit the data. All data are modeled using the triple layer model and the site-occupancy standard state; unless stated otherwise all strontium complexes are mononuclear. Strontium sorption to amorphous silica in the presence and absence of dissolved carbonate can be fit with tetradentate Sr2+ and SrOH+ complexes on the beta-plane and a monodentate Sr2+complex on the diffuse plane to account for strontium sorption at low ionic strength. Strontium sorption to goethite in the absence of dissolved carbonate can be fit with monodentate and tetradentate SrOH+ complexes and a tetradentate binuclear Sr2+ species on the beta-plane. The binuclear complex is needed to account for enhanced sorption at hgh strontium surface loadings. In the presence of dissolved carbonate additional monodentate Sr2+ and SrOH+ carbonate surface complexes on the beta-plane are needed to fit strontium sorption to goethite. Modeling strontium sorption as outer-sphere complexes is consistent with quantitative analysis of extended X-ray absorption fine structure (EXAFS) on selected sorption samples that show a single first shell of oxygen atoms around strontium indicating hydrated surface complexes at the amorphous silica and goethite surfaces. Strontium surface complexation equilibrium constants determined in this study combined with other alkaline earth surface complexation constants are used to recalibrate a predictive model based on Born solvation and crystal-chemistry theory. The model is accurate to about 0.7 log K units. More studies are needed to determine the dependence of alkaline earth sorption on ionic strength and dissolved carbonate and sulfate concentrations for the development of a robust

  12. Surface complexation model for strontium sorption to amorphous silica and goethite

    PubMed Central

    Carroll, Susan A; Roberts, Sarah K; Criscenti, Louise J; O'Day, Peggy A

    2008-01-01

    Strontium sorption to amorphous silica and goethite was measured as a function of pH and dissolved strontium and carbonate concentrations at 25°C. Strontium sorption gradually increases from 0 to 100% from pH 6 to 10 for both phases and requires multiple outer-sphere surface complexes to fit the data. All data are modeled using the triple layer model and the site-occupancy standard state; unless stated otherwise all strontium complexes are mononuclear. Strontium sorption to amorphous silica in the presence and absence of dissolved carbonate can be fit with tetradentate Sr2+ and SrOH+ complexes on the β-plane and a monodentate Sr2+complex on the diffuse plane to account for strontium sorption at low ionic strength. Strontium sorption to goethite in the absence of dissolved carbonate can be fit with monodentate and tetradentate SrOH+ complexes and a tetradentate binuclear Sr2+ species on the β-plane. The binuclear complex is needed to account for enhanced sorption at hgh strontium surface loadings. In the presence of dissolved carbonate additional monodentate Sr2+ and SrOH+ carbonate surface complexes on the β-plane are needed to fit strontium sorption to goethite. Modeling strontium sorption as outer-sphere complexes is consistent with quantitative analysis of extended X-ray absorption fine structure (EXAFS) on selected sorption samples that show a single first shell of oxygen atoms around strontium indicating hydrated surface complexes at the amorphous silica and goethite surfaces. Strontium surface complexation equilibrium constants determined in this study combined with other alkaline earth surface complexation constants are used to recalibrate a predictive model based on Born solvation and crystal-chemistry theory. The model is accurate to about 0.7 log K units. More studies are needed to determine the dependence of alkaline earth sorption on ionic strength and dissolved carbonate and sulfate concentrations for the development of a robust surface

  13. Surface Complexation Model for Strontium Sorption to Amorphous Silica and Goethite

    SciTech Connect

    Carroll, S; Robers, S; Criscenti, L; O'Day, P

    2007-11-30

    Strontium sorption to amorphous silica and goethite was measured as a function of pH and dissolved strontium and carbonate concentrations at 25 C. Strontium sorption gradually increases from 0 to 100% from pH 6 to 10 for both phases and requires multiple outer-sphere surface complexes to fit the data. All data are modeled using the triple layer model and the site-occupancy standard state; unless stated otherwise all strontium complexes are mononuclear. Strontium sorption to amorphous silica in the presence and absence of dissolved carbonate can be fit with tetradentate Sr{sup 2+} and SrOH{sup +} complexes on the {beta}-plane and a monodentate Sr{sup 2+} complex on the diffuse plane to account for strontium sorption at low ionic strength. Strontium sorption to goethite in the absence of dissolved carbonate can be fit with monodentate and tetradentate SrOH{sup +} complexes and a tetradentate binuclear Sr{sup 2+} species on the {beta}-plane. The binuclear complex is needed to account for enhanced sorption at high strontium surface loadings. In the presence of dissolved carbonate additional monodentate Sr{sup 2+} and SrOH{sup +} carbonate surface complexes on the {beta}-plane are needed to fit strontium sorption to goethite. Modeling strontium sorption as outer-sphere complexes is consistent with quantitative analysis of extended X-ray absorption fine structure (EXAFS) on selected sorption samples that show a single first shell of oxygen atoms around strontium indicating hydrated surface complexes at the amorphous silica and goethite surfaces. Strontium surface complexation equilibrium constants determined in this study combined with other alkaline earth surface complexation constants are used to recalibrate a predictive model based on Born solvation and crystal-chemistry theory. The model is accurate to about 0.7 log K units. More studies are needed to determine the dependence of alkaline earth sorption on ionic strength and dissolved carbonate and sulfate

  14. Alpha-Particle-Induced Complex Chromosome Exchanges Transmitted through Extra-Thymic Lymphopoiesis In Vitro Show Evidence of Emerging Genomic Instability

    PubMed Central

    Sumption, Natalia; Goodhead, Dudley T.; Anderson, Rhona M.

    2015-01-01

    Human exposure to high-linear energy transfer α-particles includes environmental (e.g. radon gas and its decay progeny), medical (e.g. radiopharmaceuticals) and occupational (nuclear industry) sources. The associated health risks of α-particle exposure for lung cancer are well documented however the risk estimates for leukaemia remain uncertain. To further our understanding of α-particle effects in target cells for leukaemogenesis and also to seek general markers of individual exposure to α-particles, this study assessed the transmission of chromosomal damage initially-induced in human haemopoietic stem and progenitor cells after exposure to high-LET α-particles. Cells surviving exposure were differentiated into mature T-cells by extra-thymic T-cell differentiation in vitro. Multiplex fluorescence in situ hybridisation (M-FISH) analysis of naïve T-cell populations showed the occurrence of stable (clonal) complex chromosome aberrations consistent with those that are characteristically induced in spherical cells by the traversal of a single α-particle track. Additionally, complex chromosome exchanges were observed in the progeny of irradiated mature T-cell populations. In addition to this, newly arising de novo chromosome aberrations were detected in cells which possessed clonal markers of α-particle exposure and also in cells which did not show any evidence of previous exposure, suggesting ongoing genomic instability in these populations. Our findings support the usefulness and reliability of employing complex chromosome exchanges as indicators of past or ongoing exposure to high-LET radiation and demonstrate the potential applicability to evaluate health risks associated with α-particle exposure. PMID:26252014

  15. Preserving the supersaturation generation capability of amorphous drug-polysaccharide nanoparticle complex after freeze drying.

    PubMed

    Kiew, Tie Yi; Cheow, Wean Sin; Hadinoto, Kunn

    2015-04-30

    While the supersaturation generation capability of amorphous nanopharmaceuticals (NPs) in their aqueous suspension form has been well established, their supersaturation generation is adversely affected after drying. Herein we investigated the effects of freeze drying on the supersaturation generation capability of a new class of amorphous NPs referred to as drug nanoplex prepared and stabilized by electrostatic complexation of drug molecules with polysaccharides (dextran sulfate). Using ciprofloxacin as the model drug, two types of freeze-drying adjuvants were investigated, i.e., (1) highly water-soluble excipient (trehalose, mannitol), whose role was to prevent irreversible NPs aggregations upon drying, and (2) crystallization inhibitor (hydroxypropylmethylcellulose (HPMC)), whose role was to suppress crystallization of the dissolved drug and the remaining solid phase. The results showed that dual-adjuvant formulations (i.e. trehalose-HPMC and mannitol-HPMC) were required to preserve the supersaturation generation capability of the drug nanoplex suspension after drying. Freeze drying with only one adjuvant type, or incorporating HPMC as physical mixtures with the freeze-dried nanoplex, were ineffective in preserving the supersaturation. The dual-adjuvant formulations produced prolonged supersaturation levels over 240min at ≈6-8× of the saturation solubility with comparable area under the curve (AUC) in the concentration versus time plot as that exhibited by the suspension form. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. Amorphous solid dispersion studies of camptothecin-cyclodextrin inclusion complexes in PEG 6000.

    PubMed

    Fatmi, Sofiane; Bournine, Lamine; Iguer-Ouada, Mokrane; Lahiani-Skiba, Malika; Bouchal, Fatiha; Skiba, Mohamed

    2015-01-01

    Abstract: The present work focused on the solubility enhancement of the poorly water-soluble anti-cancer agent camptothecin which, in its natural state, presents poor solubility inducing lack of activity with a marked toxicity. A new approach is adopted by using a ternary system including camptothecin (CPT) and cyclodextrins (CDs) dispersed in polyethylene glycol (PEG) 6000. Camptothecin solubility variations in the presence of α-CD, β-CD, γ-CD, hydroxypropyl-α-CD (HPα-CD), hydroxypropyl-β-CD (HPβ-CD), permethyl-β-CD (PMβ-CD) and sulfobutyl ether-β-CD (SBEβ-CD), were evaluated by Higuchi solubility experiments. In the second part, the most efficient camptothecin/P-CDs binary systems, mainly HPβ-CD and PMβ-CD, were dispersed in PEG 6000. In addition to a drug release and modeling evaluation, the CPT interactions with CDs and PEG 6000 to prepared the amorphous solid dispersion in the binary and ternary systems were investigated by Fourier transformed infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analyses (TGA) and X-ray powder diffraction (XRPD). The results showed that HPβ-CD and PMβ-CD were the most efficient for camptothecin solubilization with highest apparent equilibrium constants. Dissolution studies showed that percentage of CPT alone after two hour in 0.1 M HCI medium, did not exceed 16%, whereas under the same conditions, CPT/PMβ-CD complex reached 76%. When dispersing the binary systems CPT/β-CDs in PEG 6000, the velocity and the percentage of CPT release were considerably improved whatever the CD used, reaching the same value of 85%. The binary and ternary systems characterization demonstrated that CPT inclused into the CDs cavity, replacing the water molecules. Furthermore, a drug transition from crystalline to amorphous form was obtained when solid dispersion is realized. The present work demonstrated that ternary complexes are promising systems for CPT encapsulation, and offer opportunities to

  17. Effects of chitosan molecular weight on the physical and dissolution characteristics of amorphous curcumin-chitosan nanoparticle complex.

    PubMed

    Yu, Hong; Nguyen, Minh-Hiep; Hadinoto, Kunn

    2017-09-11

    To investigate the effects of varying molecular weight (MW) of chitosan (CHI) used in the complexation with curcumin (CUR) on the physical and dissolution characteristics of the amorphous CUR-CHI nanoparticle complex produced. Amorphous CUR-CHI nanoparticle complex (or CUR nanoplex in short) recently emerged as a promising bioavailability enhancement strategy of CUR attributed to its fast dissolution, supersaturation generation capability, and simple preparation. Existing CUR nanoplex prepared using low MW CHI, however, exhibited poor colloidal stability during storage. Herein we hypothesized that the colloidal stability could be improved by using CHI of higher MW. The effects of this approach on the nanoplex's other characteristics were simultaneously investigated. The CUR nanoplex was prepared by electrostatically driven self-assembled complexation between CUR and oppositely charged CHI of three different MWs (i.e. low, medium, and high). Besides colloidal stability, the effects of MW variation were investigated for the nanoplex's (1) other physical characteristics (i.e. size, zeta potential, CUR payload, amorphous state stability), (2) preparation efficiency (i.e. CUR utilization rate, yield), and (3) dissolutions under sink condition and supersaturation generation. CUR nanoplex prepared using CHI of high MW exhibited improved colloidal stability, larger size, superior morphology, and prolonged supersaturation generation. On the other hand, the effects of MW variation on the payload, amorphous state stability, preparation efficiency, and dissolution under sink condition were found to be insignificant. Varying MW of CHI used was an effective means to improve certain aspects of the CUR nanoplex characteristics with minimal adverse effects on the others.

  18. Encapsulation of CO2 into amorphous and crystalline α-cyclodextrin powders and the characterization of the complexes formed.

    PubMed

    Ho, Thao M; Howes, Tony; Bhandari, Bhesh R

    2015-11-15

    Carbon dioxide complexation was undertaken into solid matrices of amorphous and crystalline α-cyclodextrin (α-CD) powders, under various pressures (0.4-1.6 MPa) and time periods (4-96 h). The results show that the encapsulation capacity of crystalline α-CD was significantly lower than that of amorphous α-CD at low pressure and short time (0.4-0.8 MPa and 4-24 h), but was markedly enhanced with an increase of pressure and prolongation of encapsulation time. For each pressure level tested, the time required to reach a near equilibrium encapsulation capacity of the crystalline powder was around 48 h, which was much longer than that of the amorphous one, which only required about 8h. The inclusion complex formation of both types of α-CD powders was confirmed by the appearance of a CO2 peak on the FTIR and NMR spectra. Moreover, inclusion complexes were also characterized by DSC, TGA, SEM and X-ray analyses.

  19. First principles-based multiparadigm, multiscale strategy for simulating complex materials processes with applications to amorphous SiC films

    SciTech Connect

    Naserifar, Saber; Goddard, William A.; Tsotsis, Theodore T.; Sahimi, Muhammad

    2015-05-07

    Progress has recently been made in developing reactive force fields to describe chemical reactions in systems too large for quantum mechanical (QM) methods. In particular, ReaxFF, a force field with parameters that are obtained solely from fitting QM reaction data, has been used to predict structures and properties of many materials. Important applications require, however, determination of the final structures produced by such complex processes as chemical vapor deposition, atomic layer deposition, and formation of ceramic films by pyrolysis of polymers. This requires the force field to properly describe the formation of other products of the process, in addition to yielding the final structure of the material. We describe a strategy for accomplishing this and present an example of its use for forming amorphous SiC films that have a wide variety of applications. Extensive reactive molecular dynamics (MD) simulations have been carried out to simulate the pyrolysis of hydridopolycarbosilane. The reaction products all agree with the experimental data. After removing the reaction products, the system is cooled down to room temperature at which it produces amorphous SiC film, for which the computed radial distribution function, x-ray diffraction pattern, and the equation of state describing the three main SiC polytypes agree with the data and with the QM calculations. Extensive MD simulations have also been carried out to compute other structural properties, as well the effective diffusivities of light gases in the amorphous SiC film.

  20. First principles-based multiparadigm, multiscale strategy for simulating complex materials processes with applications to amorphous SiC films

    NASA Astrophysics Data System (ADS)

    Naserifar, Saber; Goddard, William A.; Tsotsis, Theodore T.; Sahimi, Muhammad

    2015-05-01

    Progress has recently been made in developing reactive force fields to describe chemical reactions in systems too large for quantum mechanical (QM) methods. In particular, ReaxFF, a force field with parameters that are obtained solely from fitting QM reaction data, has been used to predict structures and properties of many materials. Important applications require, however, determination of the final structures produced by such complex processes as chemical vapor deposition, atomic layer deposition, and formation of ceramic films by pyrolysis of polymers. This requires the force field to properly describe the formation of other products of the process, in addition to yielding the final structure of the material. We describe a strategy for accomplishing this and present an example of its use for forming amorphous SiC films that have a wide variety of applications. Extensive reactive molecular dynamics (MD) simulations have been carried out to simulate the pyrolysis of hydridopolycarbosilane. The reaction products all agree with the experimental data. After removing the reaction products, the system is cooled down to room temperature at which it produces amorphous SiC film, for which the computed radial distribution function, x-ray diffraction pattern, and the equation of state describing the three main SiC polytypes agree with the data and with the QM calculations. Extensive MD simulations have also been carried out to compute other structural properties, as well the effective diffusivities of light gases in the amorphous SiC film.

  1. Complex nanospherulites of zinc oxide and native amorphous boron in the lunar regolith from Mare Crisium

    NASA Astrophysics Data System (ADS)

    Mokhov, A. V.; Kartashov, P. M.; Gornostaeva, T. A.; Asadulin, En. E.; Bogatikov, O. A.

    2013-01-01

    During the study of tea-colored impact glass fragments from the sample of lunar regolith delivered to Earth by the Luna 24 automatic station by transmission electron microscopy, the composition variations of the previously described high-carbonaceous film, the presence of at least three composition types of glasses, and unusual nanospherulites with Zn-B-N-O composition were discovered. As a part of a nonuniform high-carbonaceous oxygen-bearing film, sites enriched in either Na, S, Si, or Ca were detected. All these sites, as well as the whole film, are electron-amorphous; however, crystalline graphite was also found. Two types of nanospherulites are composed of amorphous ZnO and regular interstratifications of crystalline ZnO and amorphous boron layers with insignificant participation of adsorbed nitrogen. It is supposed that the formation of zinc-boron nanospherulites was caused by a fast-flowing explosive process and probably was modulated by high-frequency acoustic oscillations in a cloud of evaporated high-temperature ionized gas during the impact event.

  2. Cost-effective alternative to nano-encapsulation: Amorphous curcumin-chitosan nanoparticle complex exhibiting high payload and supersaturation generation.

    PubMed

    Nguyen, Minh Hiep; Yu, Hong; Kiew, Tie Yi; Hadinoto, Kunn

    2015-10-01

    While the wide-ranging therapeutic activities of curcumin have been well established, its successful delivery to realize its true therapeutic potentials faces a major challenge due to its low oral bioavailability. Even though nano-encapsulation has been widely demonstrated to be effective in enhancing the bioavailability of curcumin, it is not without drawbacks (i.e. low payload and costly preparation). Herein we present a cost-effective bioavailability enhancement strategy of curcumin in the form of amorphous curcumin-chitosan nanoparticle complex (or curcumin nanoplex in short) exhibiting a high payload (>80%). The curcumin nanoplex was prepared by a simple yet highly efficient drug-polysaccharide complexation method that required only mixing of the curcumin and chitosan solutions under ambient condition. The effects of (1) pH and (2) charge ratio of chitosan to curcumin on the (i) physical characteristics of the nanoplex (i.e. size, colloidal stability and payload), (ii) complexation efficiency, and (iii) production yield were investigated from which the optimal preparation condition was determined. The nanoplex formation was found to favor low acidic pH and charge ratio below unity. At the optimal condition (i.e. pH 4.4. and charge ratio=0.8), stable curcumin nanoplex (≈260nm) was prepared at >90% complexation efficiency and ≈50% production yield. The amorphous state stability, colloidal stability, and in vitro non-cytotoxicity of the nanoplex were successfully established. The curcumin nanoplex produced prolonged supersaturation (3h) in the presence of hydroxypropyl methylcellulose (HPMC) at five times of the saturation solubility of curcumin. In addition, curcumin released from the nanoplex exhibited improved chemical stability owed to the presence of chitosan. Both results (i.e. high supersaturation and improved chemical stability) bode well for the ability of the curcumin nanoplex to enhance the bioavailability of curcumin clinically. Copyright © 2015

  3. Theoretical Investigation of OCN(-) Charge Transfer Complexes in Condensed Phase Media: Spectroscopic Properties in Amorphous Ice

    NASA Technical Reports Server (NTRS)

    Park, Jin-Young; Woon, David E.

    2004-01-01

    Density functional theory (DFT) calculations of cyanate (OCN(-)) charge-transfer complexes were performed to model the "XCN" feature observed in interstellar icy grain mantles. OCN(-) charge-transfer complexes were formed from precursor combinations of HNCO or HOCN with either NH3 or H2O. Three different solvation strategies for realistically modeling the ice matrix environment were explored, including (1) continuum solvation, (2) pure DFT cluster calculations, and (3) an ONIOM DFT/PM3 cluster calculation. The model complexes were evaluated by their ability to reproduce seven spectroscopic measurements associated with XCN: the band origin of the OCN(-) asymmetric stretching mode, shifts in that frequency due to isotopic substitutions of C, N, O, and H, plus two weak features. The continuum solvent field method produced results consistent with some of the experimental data but failed to account for other behavior due to its limited capacity to describe molecular interactions with solvent. DFT cluster calculations successfully reproduced the available spectroscopic measurements very well. In particular, the deuterium shift showed excellent agreement in complexes where OCN(-) was fully solvated. Detailed studies of representative complexes including from two to twelve water molecules allowed the exploration of various possible solvation structures and provided insights into solvation trends. Moreover, complexes arising from cyanic or isocyanic acid in pure water suggested an alternative mechanism for the formation of OCN(-) charge-transfer complexes without the need for a strong base such as NH3 to be present. An extended ONIOM (B3LYP/PM3) cluster calculation was also performed to assess the impact of a more realistic environment on HNCO dissociation in pure water.

  4. Theoretical Investigation of OCN(-) Charge Transfer Complexes in Condensed Phase Media: Spectroscopic Properties in Amorphous Ice

    NASA Technical Reports Server (NTRS)

    Park, Jin-Young; Woon, David E.

    2004-01-01

    Density functional theory (DFT) calculations of cyanate (OCN(-)) charge-transfer complexes were performed to model the "XCN" feature observed in interstellar icy grain mantles. OCN(-) charge-transfer complexes were formed from precursor combinations of HNCO or HOCN with either NH3 or H2O. Three different solvation strategies for realistically modeling the ice matrix environment were explored, including (1) continuum solvation, (2) pure DFT cluster calculations, and (3) an ONIOM DFT/PM3 cluster calculation. The model complexes were evaluated by their ability to reproduce seven spectroscopic measurements associated with XCN: the band origin of the OCN(-) asymmetric stretching mode, shifts in that frequency due to isotopic substitutions of C, N, O, and H, plus two weak features. The continuum solvent field method produced results consistent with some of the experimental data but failed to account for other behavior due to its limited capacity to describe molecular interactions with solvent. DFT cluster calculations successfully reproduced the available spectroscopic measurements very well. In particular, the deuterium shift showed excellent agreement in complexes where OCN(-) was fully solvated. Detailed studies of representative complexes including from two to twelve water molecules allowed the exploration of various possible solvation structures and provided insights into solvation trends. Moreover, complexes arising from cyanic or isocyanic acid in pure water suggested an alternative mechanism for the formation of OCN(-) charge-transfer complexes without the need for a strong base such as NH3 to be present. An extended ONIOM (B3LYP/PM3) cluster calculation was also performed to assess the impact of a more realistic environment on HNCO dissociation in pure water.

  5. Encapsulation of CO2 into amorphous alpha-cyclodextrin powder at different moisture contents - Part 1: Encapsulation capacity and stability of inclusion complexes.

    PubMed

    Ho, Thao M; Howes, Tony; Bhandari, Bhesh R

    2016-07-15

    This study investigated the effects of water-induced crystallization of amorphous alpha-cyclodextrin (α-CD) powder on CO2 encapsulation at 0.4-1.6 MPa pressure for 1-72 h through the addition of water (to reach to 13, 15 and 17% wet basis, w.b.) into amorphous α-CD powder prior to the encapsulation. The results showed that the α-CD encapsulation capacity was over 1 mol CO2/mol α-CD after pressurizing for longer than 48 h. The encapsulated CO2 concentration by the addition of water was considerably higher (p<0.05) than that of amorphous α-CD powder (5.51% MC, w.b.) without an addition of water and that of crystalline α-CD powders under the same MC and encapsulation conditions. A comparison of CO2 release properties (75% relative humidity, 25 °C) from complexed powders prepared from amorphous and crystalline α-CD powders under the same conditions is also presented.

  6. Complex Amorphous Dielectrics

    SciTech Connect

    van Dover, Robert Bruce

    2014-11-22

    This work focused on synthesizing a wide range of oxides containing two or more metals, and measuring their properties. Many simple metal oxides such as zirconium oxide, have been extensively studied in the past. We developed a technique in which we create a large number of compositions simultaneously and examine their behavior to understand trends and identify high performance materials. Superior performance generally comes in the form of increased responsiveness; in the materials we have studied this may mean more electrical charge for a given voltage in a capacitor, faster switching for a given drive in a transistor, more current for a given voltage in an ionic conductor, or more current for a given illumination in a solar cell. Some of the materials we have identified may find use in decreasing the power needed to operate integrated circuits, other materials could be useful for solar power or other forms of energy conversion.

  7. Solid state characterization of azelnidipine-oxalic acid co-crystal and co-amorphous complexes: The effect of different azelnidipine polymorphs.

    PubMed

    Pan, Yahui; Pang, Wenzhe; Lv, Jie; Wang, Jing; Yang, Caiqin; Guo, Wei

    2017-05-10

    In present study, based on the two polymorphs (α and β form) of azelnidipine (AZE), 12 complexes of AZE and oxalic acid (OXA) were prepared by solvent-assisted grinding (SG) and neat powder grinding (NG) methods at the AZE/OXA molar ratios of 2:1, 1:1, and 1:2. The effect of the different polymorphs of AZE on the micro-structure of the complexes were investigated by powder X-ray diffraction (PXRD), tempreture modulated differential scanning calorimetry and thermogravimetric analysis, cryo-field emission scanning electron microscope system, fourier transform infrared (FTIR), and solid-state nuclear magnetic resonance spectroscopy. β-AZE-OXA co-crystal was produced at β-AZE/OXA molar ratio of 2:1 when SG method was used; while α-AZE was used to produce α-AZE-OXA co-crystal at same condition. However, the other 10 combinations were in co-amorphous forms, including the NG samples with α (or β)-AZE/OXA molar ratios of 2:1, 1:1 (SG and NG), and 1:2 (SG and NG). Although the XRD pattern and IR spectra of the two co-crystals showed no difference, the melting enthalpy and specific heat cp of the β-AZE-OXA co-crystal was higher than that of the α-AZE-OXA co-crystal, indicating that the numbers of solvent molecules which entered the two co-crystal lattices were different. Interestingly, obvious difference occurred in the IR spectra between the α-AZE-OXA and β-AZE-OXA co-amorphous systems. 1745cm(-1) wave-numbers, which were assigned to the free CO groups, appeared in the α-AZE-OXA co-amorphous systems even when just a small amount of OXA was introduced, thereby indicating the presence of different intermolecular forces in the two series of co-amorphous forms. The solubility in different media and the dissolution rate in 0.1molL(-1) HCl of the 12 complexes were determined. The dramatically improved dissolution rates of the α- and β-AZE-OXA 1:2 (NG) combinations in vitro showed potential in improving the physicochemical properties of AZE by co-amorphous complex

  8. Transformation of Graphitic and Amorphous Carbon Dust to Complex Organic Molecules in a Massive Carbon Cycle in Protostellar Nebulae

    NASA Technical Reports Server (NTRS)

    Nuth, Joseph A., III; Johnson, Natasha M.

    2012-01-01

    More than 95% of silicate minerals and other oxides found in meteorites were melted, or vaporized and recondensed in the Solar Nebula prior to their incorporation into meteorite parent bodies. Gravitational accretion energy and heating via radioactive decay further transformed oxide minerals accreted into planetesimals. In such an oxygen-rich environment the carbonaceous dust that fell into the nebula as an intimate mixture with oxide grains should have been almost completely converted to CO. While some pre-collapse, molecular-cloud carbonaceous dust does survive, much in the same manner as do pre-solar oxide grains, such materials constitute only a few percent of meteoritic carbon and are clearly distinguished by elevated D/H, N-15/N-16, C-13/C-12 ratios or noble gas patterns. Carbonaceous Dust in Meteorites: We argue that nearly all of the carbon in meteorites was synthesized in the Solar Nebula from CO and that this CO was generated by the reaction of carbonaceous dust with solid oxides, water or OH. It is probable that some fraction of carbonaceous dust that is newly synthesized in the Solar Nebula is also converted back into CO by additional thermal processing. CO processing might occur on grains in the outer nebula through irradiation of CO-containing ice coatings or in the inner nebula via Fischer-Tropsch type (FTT) reactions on grain surfaces. Large-scale transport of both gaseous reaction products and dust from the inner nebula out to regions where comets formed would spread newly formed carbonaceous materials throughout the solar nebula. Formation of Organic Carbon: Carbon dust in the ISM might easily be described as inorganic graphite or amorphous carbon, with relatively low structural abundances of H, N, O and S . Products of FTT reactions or organics produced via irradiation of icy grains contain abundant aromatic and aliphatic hydrocarbons. aldehydes, keytones, acids, amines and amides.. The net result of the massive nebular carbon cycle is to convert

  9. Encapsulation of CO2 into amorphous alpha-cyclodextrin powder at different moisture contents - Part 2: Characterization of complexed powders and determination of crystalline structure.

    PubMed

    Ho, Thao M; Howes, Tony; Jack, Kevin S; Bhandari, Bhesh R

    2016-09-01

    This study aims to characterize CO2-α-cyclodextrin (α-CD) inclusion complexes produced from amorphous α-CD powder at moisture contents (MC) close to or higher than the critical level of crystallization (e.g. 13, 15 and 17% MC on wet basis, w.b.) at 0.4 and 1.6MPa pressure for 72h. The results of (13)C NMR, SEM, DSC and X-ray analyses showed that these MC levels were high enough to induce crystallization of CO2-α-CD complexed powders during encapsulation, by which amount of CO2 encapsulated by amorphous α-CD powder was significantly increased. The formation of inclusion complexes were well confirmed by results of FTIR and (13)C NMR analyses through an appearance of a peak associated with CO2 on the FTIR (2334cm(-1)) and NMR (125.3ppm) spectra. Determination of crystal packing patterns of CO2-α-CD complexed powders showed that during crystallization, α-CD molecules were arranged in cage-type structure in which CO2 molecules were entrapped in isolated cavities.

  10. A systematic procedure to build a relaxed dense-phase atomistic representation of a complex amorphous polymer using a coarse-grained modeling approach.

    PubMed

    Li, Xianfeng; Latour, Robert A

    2009-07-31

    A systematic procedure has been developed to construct a relaxed dense-phase atomistic structure of a complex amorphous polymer. The numerical procedure consists of (1) coarse graining the atomistic model of the polymer into a mesoscopic model based on an iterative algorithm for potential inversion from distribution functions of the atomistic model, (2) relaxation of the coarse grained chain using a molecular dynamics scheme, and (3) recovery of the atomistic structure by reverse mapping based on the superposition of atomistic counterparts on the corresponding coarse grained coordinates. These methods are demonstrated by their application to construct a relaxed, dense-phase model of poly(DTB succinate), which is an amorphous tyrosine-derived biodegradable polymer that is being developed for biomedical applications. Both static and dynamic properties from the coarse-grained and atomistic simulations are analyzed and compared. The coarse-grained model, which contains the essential features of the DTB succinate structure, successfully described both local and global structural properties of the atomistic chain. The effective speedup compared to the corresponding atomistic simulation is substantially above 10(2), thus enabling simulation times to reach well into the characteristic experimental regime. The computational approach for reversibly bridging between coarse-grained and atomistic models provides an efficient method to produce relaxed dense-phase all-atom molecular models of complex amorphous polymers that can subsequently be used to study and predict the atomistic-level behavior of the polymer under different environmental conditions in order to optimally design polymers for targeted applications.

  11. Carbonate-coordinated metal complexes precede the formation of liquid amorphous mineral emulsions of divalent metal carbonates.

    PubMed

    Wolf, Stephan E; Müller, Lars; Barrea, Raul; Kampf, Christopher J; Leiterer, Jork; Panne, Ulrich; Hoffmann, Thorsten; Emmerling, Franziska; Tremel, Wolfgang

    2011-03-01

    During the mineralisation of metal carbonates MCO3 (M=Ca, Sr, Ba, Mn, Cd, Pb) liquid-like amorphous intermediates emerge. These intermediates that form via a liquid/liquid phase separation behave like a classical emulsion and are stabilized electrostatically. The occurrence of these intermediates is attributed to the formation of highly hydrated networks whose stability is mainly based on weak interactions and the variability of the metal-containing pre-critical clusters. Their existence and compositional freedom are evidenced by electrospray ionization mass spectrometry (ESI-MS). Liquid intermediates in non-classical crystallisation pathways seem to be more common than assumed.

  12. Carbonate-coordinated metal complexes precede the formation of liquid amorphous mineral emulsions of divalent metal carbonates†

    PubMed Central

    Wolf, Stephan E.; Müller, Lars; Barrea, Raul; Kampf, Christopher J.; Leiterer, Jork; Panne, Ulrich; Hoffmann, Thorsten

    2011-01-01

    During the mineralisation of metal carbonates MCO3 (M = Ca, Sr, Ba, Mn, Cd, Pb) liquid-like amorphous intermediates emerge. These intermediates that form via a liquid/liquid phase separation behave like a classical emulsion and are stabilized electrostatically. The occurrence of these intermediates is attributed to the formation of highly hydrated networks whose stability is mainly based on weak interactions and the variability of the metal-containing pre-critical clusters. Their existence and compositional freedom are evidenced by electrospray ionization mass spectrometry (ESI-MS). Liquid intermediates in non-classical crystallisation pathways seem to be more common than assumed. PMID:21218241

  13. Analytical Applications Of Particle-Induced X-Ray Emission (PIXE)

    SciTech Connect

    Popescu, I. V.; Stihi, C.; Bancuta, A.; Dima, G.; Ene, A.; Badica, T.; Ghisa, V.

    2007-04-23

    In this paper a complex study of the capabilities of Particle-Induced X-ray Emission (PIXE) technique for the determination of major, minor and trace constituents of metallurgical, biological and environmental samples has been done. The elements identified in the metallurgical samples (steels) using PIXE were: K, Ca, V, Cr, Mn, Fe, Co, Cu, Ni, Zn, W, Ga, As, Pb, Mo, Rb, In, Rh, Zr, Pd, Nb, Sn and Sb. In the investigated biological and environmental samples (vegetals leaves, soil and mosses) PIXE analysis allowed determination of: S, Cl, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, As, Hg and Pb.

  14. Analytical Applications Of Particle-Induced X-Ray Emission (PIXE)

    NASA Astrophysics Data System (ADS)

    Popescu, I. V.; Ene, A.; Stihi, C.; Bancuta, A.; Dima, G.; Badica, T.; Ghisa, V.

    2007-04-01

    In this paper a complex study of the capabilities of Particle-Induced X-ray Emission (PIXE) technique for the determination of major, minor and trace constituents of metallurgical, biological and environmental samples has been done. The elements identified in the metallurgical samples (steels) using PIXE were: K, Ca, V, Cr, Mn, Fe, Co, Cu, Ni, Zn, W, Ga, As, Pb, Mo, Rb, In, Rh, Zr, Pd, Nb, Sn and Sb. In the investigated biological and environmental samples (vegetals leaves, soil and mosses) PIXE analysis allowed determination of: S, Cl, K, Ca, Ti, Mn, Fe, Ni, Cu, Zn, As, Hg and Pb.

  15. The EPIC-MOS Particle-Induced Background Spectrum

    NASA Technical Reports Server (NTRS)

    Kuntz, K. D.; Snowden, S. L.

    2006-01-01

    We have developed a method for constructing a spectrum of the particle-induced instrumental background of the XMM-Newton EPIC MOS detectors that can be used for observations of the diffuse background and extended sources that fill a significant fraction of the instrument field of view. The strength and spectrum of the particle-induced background, that is, the background due to the interaction of particles with the detector and the detector surroundings, is temporally variable as well as spatially variable over individual chips. Our method uses a combination of the filter-wheel-closed data and a database of unexposed-region data to construct a spectrum of the "quiescent" background. We show that, using this method of background subtraction, the differences between independent observations of the same region of "blank sky" are consistent with the statistical uncertainties except when there is clear evidence of solar wind charge exchange emission. We use the blank sky observations to show that contamination by SWCX emission is a strong function of the solar wind proton flux, and that observations through the flanks of the magnetosheath appear to be contaminated only at much higher solar wind fluxes. We have also developed a spectral model of the residual soft proton flares, which allows their effects to be removed to a substantial degree during spectral fitting.

  16. Amorphous nickel-cobalt complexes hybridized with 1T-phase molybdenum disulfide via hydrazine-induced phase transformation for water splitting

    PubMed Central

    Li, Haoyi; Chen, Shuangming; Jia, Xiaofan; Xu, Biao; Lin, Haifeng; Yang, Haozhou; Song, Li; Wang, Xun

    2017-01-01

    Highly active and robust eletcrocatalysts based on earth-abundant elements are desirable to generate hydrogen and oxygen as fuels from water sustainably to replace noble metal materials. Here we report an approach to synthesize porous hybrid nanostructures combining amorphous nickel-cobalt complexes with 1T phase molybdenum disulfide (MoS2) via hydrazine-induced phase transformation for water splitting. The hybrid nanostructures exhibit overpotentials of 70 mV for hydrogen evolution and 235 mV for oxygen evolution at 10 mA cm−2 with long-term stability, which have superior kinetics for hydrogen- and oxygen-evolution with Tafel slope values of 38.1 and 45.7 mV dec−1. Moreover, we achieve 10 mA cm−2 at a low voltage of 1.44 V for 48 h in basic media for overall water splitting. We propose that such performance is likely due to the complete transformation of MoS2 to metallic 1T phase, high porosity and stabilization effect of nickel-cobalt complexes on 1T phase MoS2. PMID:28485395

  17. Amorphous nickel-cobalt complexes hybridized with 1T-phase molybdenum disulfide via hydrazine-induced phase transformation for water splitting

    NASA Astrophysics Data System (ADS)

    Li, Haoyi; Chen, Shuangming; Jia, Xiaofan; Xu, Biao; Lin, Haifeng; Yang, Haozhou; Song, Li; Wang, Xun

    2017-05-01

    Highly active and robust eletcrocatalysts based on earth-abundant elements are desirable to generate hydrogen and oxygen as fuels from water sustainably to replace noble metal materials. Here we report an approach to synthesize porous hybrid nanostructures combining amorphous nickel-cobalt complexes with 1T phase molybdenum disulfide (MoS2) via hydrazine-induced phase transformation for water splitting. The hybrid nanostructures exhibit overpotentials of 70 mV for hydrogen evolution and 235 mV for oxygen evolution at 10 mA cm-2 with long-term stability, which have superior kinetics for hydrogen- and oxygen-evolution with Tafel slope values of 38.1 and 45.7 mV dec-1. Moreover, we achieve 10 mA cm-2 at a low voltage of 1.44 V for 48 h in basic media for overall water splitting. We propose that such performance is likely due to the complete transformation of MoS2 to metallic 1T phase, high porosity and stabilization effect of nickel-cobalt complexes on 1T phase MoS2.

  18. The significance of nanoparticles in particle-induced pulmonary fibrosis

    PubMed Central

    Byrne, James D; Baugh, John A

    2008-01-01

    Exposure to airborne nanoparticles contributes to many chronic pulmonary diseases. Nanoparticles, classified as anthropogenic and natural particles, and fibers of diameters less than 100 nm, have unrestricted access to most areas of the lung due to their size. Size relates to the deposition efficiency of the particle, with particles in the nano-range having the highest efficiencies. The deposition of nanoparticles in the lung can lead to chronic inflammation, epithelial injury, and further to pulmonary fibrosis. Cases of particle-induced pulmonary fibrosis, namely pneumoconiosis, are mostly occupationally influenced, and continue to be documented around the world. The tremendous growth of nanotechnology, however, has spurred fears of increased rates of pulmonary diseases, especially fibrosis. The severity of toxicological consequences warrants further examination of the effects of nanoparticles in humans, possible treatments and increased regulatory measures. PMID:18523535

  19. Amorphous metal composites

    DOEpatents

    Byrne, Martin A.; Lupinski, John H.

    1984-01-01

    An improved amorphous metal composite and process of making the composite. The amorphous metal composite comprises amorphous metal (e.g. iron) and a low molecular weight thermosetting polymer binder. The process comprises placing an amorphous metal in particulate form and a thermosetting polymer binder powder into a container, mixing these materials, and applying heat and pressure to convert the mixture into an amorphous metal composite.

  20. Mechanisms of particle-induced activation of alveolar macrophages.

    PubMed

    Gercken, G; Berg, I; Dörger, M; Schlüter, T

    1996-11-01

    Bovine alveolar macrophages were exposed in vitro to quartz dusts, metal-containing dusts or silica particles coated with a single metal oxide. The release of reactive oxygen intermediates (ROI) was measured in short-term incubations (90 min). The secretion of both ROI was markedly enhanced by silica particles coated with vanadium oxide and lowered by copper oxide-coated particles. The particle-induced ROI release was significantly decreased by the inhibition of protein kinase C (PKC) as well as phospholipase A2, suggesting the involvement of both enzymes in the NADPH oxidase activation. Quartz dusts induced a transient increase of free cytosolic calcium ion concentration, slight intracellular acidification, and depolarization of the plasma membrane. In the presence of EGTA or verapamil the rise of [Ca2+]i was diminished, suggesting an influx of extracellular calcium ions. The PKC inhibitor GF 109203X did not inhibit the quartz-induced calcium rise, while both the cytosolic acidification and depolarization were prevented. BSA-coating of the quartz particles abolished the calcium influx as well as the decrease of pHi, and possibly hyperpolarized the plasma membrane.

  1. Theory of trapped-particle-induced resistive fluid turbulence

    SciTech Connect

    Biglari, H.; Diamond, P.H.

    1987-12-01

    A theory of anomalous electron heat transport, evolving from trapped-particle-induced resistive interchange modes, is proposed. The latter are a new branch of the resistive interchange-ballooning family of instabilities, destabilized when the pressure carried by the unfavorably drifting trapped particles is sufficiently large to overcome stabilizing contributions coming from favorable average curvature. Expressions for the turbulent heat diffusivity and anomalous electron thermal conductivity at saturation are derived for two regimes of trapped-particle energy: (I) a moderately energetic regime, which is ''fluidlike'' in the sense that the unstable mode grows faster than the time that it takes for particles in this energy range to precess once around the torus, and (II) a highly energetic regime, where the trapped species has sufficiently high energy as to be able to interact resonantly with the mode. Unlike previous theories of anomalous transport, the estimates of diffusion and transport obtained here are self-consistent since the trapped particles do not ''see'' the magnetic flutter due to their rapid bounce motion. The theory is valid for moderate electron-temperature, high ion-temperature (auxiliary heated) plasmas and as such, is relevant for present- and future-generation experimental fusion devices.

  2. Theory of trapped-particle-induced resistive fluid turbulence

    SciTech Connect

    Biglari, H.; Diamond, P.H.

    1987-05-01

    A theory of anomalous electron heat transport, evolving from trapped-particle-induced resistive interchange modes, is proposed. These latter are a new branch of the resistive interchange-ballooning family of instabilities, destabilized when the pressure carried by the unfavorably-drifting trapped particles is sufficiently large to overcome stabilizing contributions coming from favorable average curvature. Expressions for the turbulent heat diffusivity and anomalous electron thermal conductivity at saturation are derived for two regimes of trapped particle energy: (1) a moderately-energetic regime, which is ''fluid-like'' in the sense that the unstable mode grows faster than the time that it takes for particles in this energy range to precess once around the torus; and (2) a highly-energetic regime, where the trapped species has sufficiently high energy as to be able to resonantly interact with the mode. Unlike previous theories of anomalous transport, the estimates of diffusion and transport obtained here are self-consistent, since the trapped particles do not ''see'' the magnetic flutter due to their rapid bounce motion. The theory is valid for moderate electron-temperature, high ion-temperature (auxiliary-heated) plasmas, and as such, is relevant for present and future-generation experimental fusion devices.

  3. Intrinsic particle-induced lateral transport in microchannels

    PubMed Central

    Amini, Hamed; Sollier, Elodie; Weaver, Westbrook M.; Di Carlo, Dino

    2012-01-01

    In microfluidic systems at low Reynolds number, the flow field around a particle is assumed to maintain fore-aft symmetry, with fluid diverted by the presence of a particle, returning to its original streamline downstream. This current model considers particles as passive components of the system. However, we demonstrate that at finite Reynolds number, when inertia is taken into consideration, particles are not passive elements in the flow but significantly disturb and modify it. In response to the flow field, particles translate downstream while rotating. The combined effect of the flow of fluid around particles, particle rotation, channel confinement (i.e., particle dimensions approaching those of the channel), and finite fluid inertia creates a net recirculating flow perpendicular to the primary flow direction within straight channels that resembles the well-known Dean flow in curved channels. Significantly, the particle generating this flow remains laterally fixed as it translates downstream and only the fluid is laterally transferred. Therefore, as the particles remain inertially focused, operations can be performed around the particles in a way that is compatible with downstream assays such as flow cytometry. We apply this particle-induced transfer to perform fluid switching and mixing around rigid microparticles as well as deformable cells. This transport phenomenon, requiring only a simple channel geometry with no external forces to operate, offers a practical approach for fluid transfer at high flow rates with a wide range of applications, including sample preparation, flow reaction, and heat transfer. PMID:22761309

  4. Universal features of amorphous plasticity

    NASA Astrophysics Data System (ADS)

    Budrikis, Zoe; Castellanos, David Fernandez; Sandfeld, Stefan; Zaiser, Michael; Zapperi, Stefano

    2017-07-01

    Plastic yielding of amorphous solids occurs by power-law distributed deformation avalanches whose universality is still debated. Experiments and molecular dynamics simulations are hampered by limited statistical samples, and although existing stochastic models give precise exponents, they require strong assumptions about fixed deformation directions, at odds with the statistical isotropy of amorphous materials. Here, we introduce a fully tensorial, stochastic mesoscale model for amorphous plasticity that links the statistical physics of plastic yielding to engineering mechanics. It captures the complex shear patterning observed for a wide variety of deformation modes, as well as the avalanche dynamics of plastic flow. Avalanches are described by universal size exponents and scaling functions, avalanche shapes, and local stability distributions, independent of system dimensionality, boundary and loading conditions, and stress state. Our predictions consistently differ from those of mean-field depinning models, providing evidence that plastic yielding is a distinct type of critical phenomenon.

  5. Universal features of amorphous plasticity

    PubMed Central

    Budrikis, Zoe; Castellanos, David Fernandez; Sandfeld, Stefan; Zaiser, Michael; Zapperi, Stefano

    2017-01-01

    Plastic yielding of amorphous solids occurs by power-law distributed deformation avalanches whose universality is still debated. Experiments and molecular dynamics simulations are hampered by limited statistical samples, and although existing stochastic models give precise exponents, they require strong assumptions about fixed deformation directions, at odds with the statistical isotropy of amorphous materials. Here, we introduce a fully tensorial, stochastic mesoscale model for amorphous plasticity that links the statistical physics of plastic yielding to engineering mechanics. It captures the complex shear patterning observed for a wide variety of deformation modes, as well as the avalanche dynamics of plastic flow. Avalanches are described by universal size exponents and scaling functions, avalanche shapes, and local stability distributions, independent of system dimensionality, boundary and loading conditions, and stress state. Our predictions consistently differ from those of mean-field depinning models, providing evidence that plastic yielding is a distinct type of critical phenomenon. PMID:28671191

  6. Universal features of amorphous plasticity.

    PubMed

    Budrikis, Zoe; Castellanos, David Fernandez; Sandfeld, Stefan; Zaiser, Michael; Zapperi, Stefano

    2017-07-03

    Plastic yielding of amorphous solids occurs by power-law distributed deformation avalanches whose universality is still debated. Experiments and molecular dynamics simulations are hampered by limited statistical samples, and although existing stochastic models give precise exponents, they require strong assumptions about fixed deformation directions, at odds with the statistical isotropy of amorphous materials. Here, we introduce a fully tensorial, stochastic mesoscale model for amorphous plasticity that links the statistical physics of plastic yielding to engineering mechanics. It captures the complex shear patterning observed for a wide variety of deformation modes, as well as the avalanche dynamics of plastic flow. Avalanches are described by universal size exponents and scaling functions, avalanche shapes, and local stability distributions, independent of system dimensionality, boundary and loading conditions, and stress state. Our predictions consistently differ from those of mean-field depinning models, providing evidence that plastic yielding is a distinct type of critical phenomenon.

  7. Alpha Particles Induce Apoptosis through the Sphingomyelin Pathway

    PubMed Central

    Seideman, Jonathan H.; Stancevic, Branka; Rotolo, Jimmy A.; McDevitt, Michael R.; Howell, Roger W.; Kolesnick, Richard N.; Scheinberg, David A.

    2011-01-01

    The sphingomyelin pathway involves the enzymatic cleavage of sphingomyelin to produce ceramide, a second messenger that serves as a key mediator in the rapid apoptotic response to various cell stressors. Low-linear energy transfer (LET) γ radiation can initiate this pathway, independent of DNA damage, via the cell membrane. Whether short-ranged, high-LET a particles, which are of interest as potent environmental carcinogens, radiotherapies and potential components of dirty bombs, can act through this mechanism to signal apoptosis is unknown. Here we show that irradiation of Jurkat cells with a particles emitted by the 225Ac-DOTA-anti-CD3 IgG antibody construct results in dose-dependent apoptosis. This apoptosis was significantly reduced by pretreating cells with cholesterol-depleting nystatin, a reagent known to inhibit ceramide signaling by interfering with membrane raft coalescence and ceramide-rich platform generation. The effects of nystatin on α-particle-induced apoptosis were related to disruption of the ceramide pathway and not to microdosimetry alterations, because similar results were obtained after external irradiation of the cells with a broad beam of collimated a particles using a planar 241Am source. External irradiation allowed for more precise control of the dosimetry and geometry of the irradiation, independent of antibody binding or cell internalization kinetics. Mechanistically consistent with these findings, Jurkat cells rapidly increased membrane concentrations of ceramide after external irradiation with an average of five α-particle traversals per cell. These data indicate that a particles can activate the sphingomyelin pathway to induce apoptosis. PMID:21631289

  8. Alpha particles induce apoptosis through the sphingomyelin pathway.

    PubMed

    Seideman, Jonathan H; Stancevic, Branka; Rotolo, Jimmy A; McDevitt, Michael R; Howell, Roger W; Kolesnick, Richard N; Scheinberg, David A

    2011-10-01

    The sphingomyelin pathway involves the enzymatic cleavage of sphingomyelin to produce ceramide, a second messenger that serves as a key mediator in the rapid apoptotic response to various cell stressors. Low-linear energy transfer (LET) γ radiation can initiate this pathway, independent of DNA damage, via the cell membrane. Whether short-ranged, high-LET α particles, which are of interest as potent environmental carcinogens, radiotherapies and potential components of dirty bombs, can act through this mechanism to signal apoptosis is unknown. Here we show that irradiation of Jurkat cells with α particles emitted by the ²²⁵Ac-DOTA-anti-CD3 IgG antibody construct results in dose-dependent apoptosis. This apoptosis was significantly reduced by pretreating cells with cholesterol-depleting nystatin, a reagent known to inhibit ceramide signaling by interfering with membrane raft coalescence and ceramide-rich platform generation. The effects of nystatin on α-particle-induced apoptosis were related to disruption of the ceramide pathway and not to microdosimetry alterations, because similar results were obtained after external irradiation of the cells with a broad beam of collimated α particles using a planar ²⁴¹Am source. External irradiation allowed for more precise control of the dosimetry and geometry of the irradiation, independent of antibody binding or cell internalization kinetics. Mechanistically consistent with these findings, Jurkat cells rapidly increased membrane concentrations of ceramide after external irradiation with an average of five α-particle traversals per cell. These data indicate that α particles can activate the sphingomyelin pathway to induce apoptosis.

  9. Amorphization strategy affects the stability and supersaturation profile of amorphous drug nanoparticles.

    PubMed

    Cheow, Wean Sin; Kiew, Tie Yi; Yang, Yue; Hadinoto, Kunn

    2014-05-05

    Amorphous drug nanoparticles have recently emerged as a promising bioavailability enhancement strategy of poorly soluble drugs attributed to the high supersaturation solubility generated by the amorphous state and fast dissolution afforded by the nanoparticles. Herein we examine the effects of two amorphization strategies in the nanoscale, i.e., (1) molecular mobility restrictions and (2) high energy surface occupation, both by polymer excipient stabilizers, on the (i) morphology, (ii) colloidal stability, (iii) drug loading, (iv) amorphous state stability after three-month storage, and (v) in vitro supersaturation profiles, using itraconazole (ITZ) as the model drug. Drug-polyelectrolyte complexation is employed in the first strategy to prepare amorphous ITZ nanoparticles using dextran sulfate as the polyelectrolyte (ITZ nanoplex), while the second strategy employs pH-shift precipitation using hydroxypropylmethylcellulose as the surface stabilizer (nano-ITZ), with both strategies resulting in >90% ITZ utilization. Both amorphous ITZ nanoparticles share similar morphology (∼300 nm spheres) with the ITZ nanoplex exhibiting better colloidal stability, albeit at lower ITZ loading (65% versus 94%), due to the larger stabilizer amount used. The ITZ nanoplex also exhibits superior amorphous state stability, attributed to the ITZ molecular mobility restriction by electrostatic complexation with dextran sulfate. The higher stability, however, is obtained at the expense of slower supersaturation generation, which is maintained over a prolonged period, compared to the nano-ITZ. The present results signify the importance of selecting the optimal amorphization strategy, in addition to formulating the excipient stabilizers, to produce amorphous drug nanoparticles having the desired characteristics.

  10. Theory of amorphous ices

    PubMed Central

    Limmer, David T.; Chandler, David

    2014-01-01

    We derive a phase diagram for amorphous solids and liquid supercooled water and explain why the amorphous solids of water exist in several different forms. Application of large-deviation theory allows us to prepare such phases in computer simulations. Along with nonequilibrium transitions between the ergodic liquid and two distinct amorphous solids, we establish coexistence between these two amorphous solids. The phase diagram we predict includes a nonequilibrium triple point where two amorphous phases and the liquid coexist. Whereas the amorphous solids are long-lived and slowly aging glasses, their melting can lead quickly to the formation of crystalline ice. Further, melting of the higher density amorphous solid at low pressures takes place in steps, transitioning to the lower-density glass before accessing a nonequilibrium liquid from which ice coarsens. PMID:24858957

  11. Nanocrystal dispersed amorphous alloys

    NASA Technical Reports Server (NTRS)

    Perepezko, John H. (Inventor); Allen, Donald R. (Inventor); Foley, James C. (Inventor)

    2001-01-01

    Compositions and methods for obtaining nanocrystal dispersed amorphous alloys are described. A composition includes an amorphous matrix forming element (e.g., Al or Fe); at least one transition metal element; and at least one crystallizing agent that is insoluble in the resulting amorphous matrix. During devitrification, the crystallizing agent causes the formation of a high density nanocrystal dispersion. The compositions and methods provide advantages in that materials with superior properties are provided.

  12. Tritium in amorphous silicon

    SciTech Connect

    Sidhu, L.S.; Kosteski, T.; O`Leary, S.K.; Gaspari, F.; Zukotynski, S.; Kherani, N.P.; Shmadya, W.

    1996-12-31

    Preliminary results on infrared and luminescence measurements of tritium incorporated amorphous silicon are reported. Tritium is an unstable isotope that readily substitutes hydrogen in the amorphous silicon network. Due to its greater mass, bonded tritium is found to introduce new stretching modes in the infrared spectrum. Inelastic collisions between the beta particles, produced as a result of tritium decay, and the amorphous silicon network, results in the generation of excess electron-hole pairs. Radiative recombination of these carriers is observed.

  13. Progranulin suppresses titanium particle induced inflammatory osteolysis by targeting TNFα signaling

    PubMed Central

    Zhao, Yun-peng; Wei, Jian-lu; Tian, Qing-yun; Liu, Alexander Tianxing; Yi, Young-Su; Einhorn, Thomas A.; Liu, Chuan-ju

    2016-01-01

    Aseptic loosening is a major complication of prosthetic joint surgery, characterized by chronic inflammation, pain, and osteolysis surrounding the bone-implant interface. Progranulin (PGRN) is known to have anti-inflammatory action by binding to Tumor Necrosis Factor (TNF) receptors and antagonizing TNFα. Here we report that titanium particles significantly induced PGRN expression in RAW264.7 cells and also in a mouse air-pouch model of inflammation. PGRN-deficiency enhanced, whereas administration of recombinant PGRN effectively inhibited, titanium particle-induced inflammation in an air pouch model. In addition, PGRN also significantly inhibited titanium particle-induced osteoclastogenesis and calvarial osteolysis in vitro, ex vivo and in vivo. Mechanistic studies demonstrated that the inhibition of PGRN on titanium particle induced-inflammation is primarily via neutralizing the titanium particle-activated TNFα/NF-κB signaling pathway and this is evidenced by the suppression of particle-induced IκB phosphorylation, NF-κB p65 nuclear translocation, and activity of the NF-κB-specific reporter gene. Collectively, these findings not only demonstrate that PGRN plays an important role in inhibiting titanium particle-induced inflammation, but also provide a potential therapeutic agent for the prevention of wear debris-induced inflammation and osteolysis. PMID:26864916

  14. Progranulin suppresses titanium particle induced inflammatory osteolysis by targeting TNFα signaling.

    PubMed

    Zhao, Yun-peng; Wei, Jian-lu; Tian, Qing-yun; Liu, Alexander Tianxing; Yi, Young-su; Einhorn, Thomas A; Liu, Chuan-ju

    2016-02-11

    Aseptic loosening is a major complication of prosthetic joint surgery, characterized by chronic inflammation, pain, and osteolysis surrounding the bone-implant interface. Progranulin (PGRN) is known to have anti-inflammatory action by binding to Tumor Necrosis Factor (TNF) receptors and antagonizing TNFα. Here we report that titanium particles significantly induced PGRN expression in RAW264.7 cells and also in a mouse air-pouch model of inflammation. PGRN-deficiency enhanced, whereas administration of recombinant PGRN effectively inhibited, titanium particle-induced inflammation in an air pouch model. In addition, PGRN also significantly inhibited titanium particle-induced osteoclastogenesis and calvarial osteolysis in vitro, ex vivo and in vivo. Mechanistic studies demonstrated that the inhibition of PGRN on titanium particle induced-inflammation is primarily via neutralizing the titanium particle-activated TNFα/NF-κB signaling pathway and this is evidenced by the suppression of particle-induced IκB phosphorylation, NF-κB p65 nuclear translocation, and activity of the NF-κB-specific reporter gene. Collectively, these findings not only demonstrate that PGRN plays an important role in inhibiting titanium particle-induced inflammation, but also provide a potential therapeutic agent for the prevention of wear debris-induced inflammation and osteolysis.

  15. Role of direct estrogen receptor signaling in wear particle-induced osteolysis

    PubMed Central

    Nich, Christophe; Rao, Allison J.; Valladares, Roberto D.; Li, Chenguang; Christman, Jane E.; Antonios, Joseph K.; Yao, Zhenyu; Zwingenberger, Stefan; Petite, Hervé; Hamadouche, Moussa; Goodman, Stuart B.

    2014-01-01

    Estrogen withdrawal following surgical ovariectomy was recently shown to mitigate particle-induced osteolysis in the murine calvarial model. Currently, we hypothesize that estrogen receptors (ERs) were involved in this paradoxical phenomenon. To test this hypothesis, we first evaluated polyethylene (PE) particle-induced osteolysis in the murine calvarial model, using wild type (WT) C57BL6J female mice, ERα deficient (ERαKO) mice, and WT mice either treated with 17β-estradiol (E2) or with the ER pan-antagonist ICI 182,780. According to micro-CT and histomorphometry, we showed that bone resorption was consistently altered in both ERαKO and ICI 182,780 treated mice as compared to WT and E2 groups. Then, we demonstrated that ER disruption consistently decreased both PE and polymethylmethacrylate (PMMA) particle-induced production of TNF-α by murine macrophages in vitro. Similar results were obtained following ER blockade using ICI 182,780 in RAW 264.7 and WT macrophages. ER disruption and pre treatment with ICI 182,780 resulted in a consistent down-regulation of particle-induced TNF-α mRNA expression relative to WT macrophages or untreated RAW cells. These results indicate that the response to wear particles involves estrogen receptors in female mice, as part of macrophage activation. Estrogen receptors may be considered as a future therapeutic target for particle-induced osteolysis. PMID:23113918

  16. Role of direct estrogen receptor signaling in wear particle-induced osteolysis.

    PubMed

    Nich, Christophe; Rao, Allison J; Valladares, Roberto D; Li, Chenguang; Christman, Jane E; Antonios, Joseph K; Yao, Zhenyu; Zwingenberger, Stefan; Petite, Hervé; Hamadouche, Moussa; Goodman, Stuart B

    2013-01-01

    Estrogen withdrawal following surgical ovariectomy was recently shown to mitigate particle-induced osteolysis in the murine calvarial model. Currently, we hypothesize that estrogen receptors (ERs) were involved in this paradoxical phenomenon. To test this hypothesis, we first evaluated polyethylene (PE) particle-induced osteolysis in the murine calvarial model, using wild type (WT) C57BL6J female mice, ERα deficient (ERαKO) mice, and WT mice either treated with 17β-estradiol (E2) or with the ER pan-antagonist ICI 182,780. According to micro-CT and histomorphometry, we showed that bone resorption was consistently altered in both ERαKO and ICI 182,780 treated mice as compared to WT and E2 groups. Then, we demonstrated that ER disruption consistently decreased both PE and polymethylmethacrylate (PMMA) particle-induced production of TNF-α by murine macrophages in vitro. Similar results were obtained following ER blockade using ICI 182,780 in RAW 264.7 and WT macrophages. ER disruption and pre treatment with ICI 182,780 resulted in a consistent down-regulation of particle-induced TNF-α mRNA expression relative to WT macrophages or untreated RAW cells. These results indicate that the response to wear particles involves estrogen receptors in female mice, as part of macrophage activation. Estrogen receptors may be considered as a future therapeutic target for particle-induced osteolysis. Copyright © 2012 Elsevier Ltd. All rights reserved.

  17. Evaluation of particle-induced X-ray emission and particle-induced γ-ray emission of quartz grains for forensic trace sediment analysis.

    PubMed

    Bailey, M J; Morgan, R M; Comini, P; Calusi, S; Bull, P A

    2012-03-06

    The independent verification in a forensics context of quartz grain morphological typing by scanning electron microscopy was demonstrated using particle-induced X-ray emission (PIXE) and particle-induced γ-ray emission (PIGE). Surface texture analysis by electron microscopy and high-sensitivity trace element mapping by PIXE and PIGE are independent analytical techniques for identifying the provenance of quartz in sediment samples in forensic investigations. Trace element profiling of the quartz grain matrix separately from the quartz grain inclusions served to differentiate grains of different provenance and indeed went some way toward discriminating between different quartz grain types identified in a single sample of one known forensic provenance. These results confirm the feasibility of independently verifying the provenance of critical samples from forensic cases.

  18. Trehalose amorphization and recrystallization.

    PubMed

    Sussich, Fabiana; Cesàro, Attilio

    2008-10-13

    The stability of the amorphous trehalose prepared by using several procedures is presented and discussed. Amorphization is shown to occur by melting (T(m)=215 degrees C) or milling (room temperature) the crystalline anhydrous form TRE-beta. Fast dehydration of the di-hydrate crystalline polymorph, TRE-h, also produces an amorphous phase. Other dehydration procedures of TRE-h, such as microwave treatment, supercritical extraction or gentle heating at low scan rates, give variable fractions of the polymorph TRE-alpha, that undergo amorphization upon melting (at lower temperature, T(m)=130 degrees C). Additional procedures for amorphization, such as freeze-drying, spray-drying or evaporation of trehalose solutions, are discussed. All these procedures are classified depending on the capability of the undercooled liquid phase to undergo cold crystallization upon heating the glassy state at temperatures above the glass transition temperature (T(g)=120 degrees C). The recrystallizable amorphous phase is invariably obtained by the melt of the polymorph TRE-alpha, while other procedures always give an amorphous phase that is unable to crystallize above T(g). The existence of two different categories is analyzed in terms of the transformation paths and the hypothesis that the systems may exhibit different molecular mobilities.

  19. Hydrogen in amorphous silicon

    SciTech Connect

    Peercy, P. S.

    1980-01-01

    The structural aspects of amorphous silicon and the role of hydrogen in this structure are reviewed with emphasis on ion implantation studies. In amorphous silicon produced by Si ion implantation of crystalline silicon, the material reconstructs into a metastable amorphous structure which has optical and electrical properties qualitatively similar to the corresponding properties in high-purity evaporated amorphous silicon. Hydrogen studies further indicate that these structures will accomodate less than or equal to 5 at.% hydrogen and this hydrogen is bonded predominantly in a monohydride (SiH/sub 1/) site. Larger hydrogen concentrations than this can be achieved under certain conditions, but the excess hydrogen may be attributed to defects and voids in the material. Similarly, glow discharge or sputter deposited amorphous silicon has more desirable electrical and optical properties when the material is prepared with low hydrogen concentration and monohydride bonding. Results of structural studies and hydrogen incorporation in amorphous silicon were discussed relative to the different models proposed for amorphous silicon.

  20. Hydrogenated amorphous silicon photonics

    NASA Astrophysics Data System (ADS)

    Narayanan, Karthik

    2011-12-01

    Silicon Photonics is quickly proving to be a suitable interconnect technology for meeting the future goals of on-chip bandwidth and low power requirements. However, it is not clear how silicon photonics will be integrated into CMOS chips, particularly microprocessors. The issue of integrating photonic circuits into electronic IC fabrication processes to achieve maximum flexibility and minimum complexity and cost is an important one. In order to minimize usage of chip real estate, it will be advantageous to integrate in three-dimensions. Hydrogenated amorphous silicon (a-Si:H) is emerging as a promising material for the 3-D integration of silicon photonics for on-chip optical interconnects. In addition, a-Si:H film can be deposited using CMOS compatible low temperature plasma-enhanced chemical vapor deposition (PECVD) process at any point in the fabrication process allowing maximum flexibility and minimal complexity. In this thesis, we demonstrate a-Si:H as a high performance alternate platform to crystalline silicon, enabling backend integration of optical interconnects in a hybrid photonic-electronic network-on-chip architecture. High quality passive devices are fabricated on a low-loss a-Si:H platform enabling wavelength division multiplexing schemes. We demonstrate a broadband all-optical modulation scheme based on free-carrier absorption effect, which can enable compact electro-optic modulators in a-Si:H. Furthermore, we comprehensively characterize the optical nonlinearities in a-Si:H and observe that a-Si:H exhibits enhanced nonlinearities as compared to crystalline silicon. Based on the enhanced nonlinearities, we demonstrate low-power four-wave mixing in a-Si:H waveguides enabling high speed all-optical devices in an a-Si:H platform. Finally, we demonstrate a novel data encoding scheme using thermal and all-optical tuning of silicon waveguides, increasing the spectral efficiency in an interconnect link.

  1. Amorphous pharmaceutical solids.

    PubMed

    Vranić, Edina

    2004-07-01

    Amorphous forms are, by definition, non-crystalline materials which possess no long-range order. Their structure can be thought of as being similar to that of a frozen liquid with the thermal fluctuations present in a liquid frozen out, leaving only "static" structural disorder. The amorphous solids have always been an essential part of pharmaceutical research, but the current interest has been raised by two developments: a growing attention to pharmaceutical solids in general, especially polymorphs and solvates and a revived interest in the science of glasses and the glass transition. Amorphous substances may be formed both intentionally and unintentionally during normal pharmaceutical manufacturing operations. The properties of amorphous materials can be exploited to improve the performance of pharmaceutical dosage forms, but these properties can also give rise to unwanted effects that need to be understood and managed in order for the systems to perform as required.

  2. Amorphous diamond films

    DOEpatents

    Falabella, S.

    1998-06-09

    Amorphous diamond films having a significant reduction in intrinsic stress are prepared by biasing a substrate to be coated and depositing carbon ions thereon under controlled temperature conditions. 1 fig.

  3. Amorphous metal alloy

    DOEpatents

    Wang, R.; Merz, M.D.

    1980-04-09

    Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

  4. Influence of resistivity on energetic trapped particle-induced internal kink modes

    SciTech Connect

    Biglari, H.; Chen, L.

    1986-01-01

    The influence of resistivity on energetic trapped particle-induced internal kink modes, dubbed ''fishbones'' in the literature, explored. A general dispersion relation, which recovers the ideal theory in its appropriate limit, is derived and analyzed. Implications of the theory for present generation fusion devices such as the Joint European Torus are discussed. 8 refs., 2 figs.

  5. 14th International Conference on Particle Induced X-ray Emission ("PIXE 2015")

    NASA Astrophysics Data System (ADS)

    Przybyłowicz, Wojciech Józef; Pineda-Vargas, Carlos

    2015-11-01

    This special issue of Nuclear Instruments and Methods in Physics Research B contains the proceedings of the 14th International Conference on Particle Induced X-ray Emission ("PIXE 2015") that was held in Somerset West (South Africa) from 25th February to 3rd March 2015.

  6. URBAN PARTICLE-INDUCED PULMONARY ARTERY CONSTRUCTION IS MEDIATED BY SUPEROXIDE PRODUCTION

    EPA Science Inventory

    URBAN PARTICLE-INDUCED PULMONARY ARTERY CONSTRICTION IS MEDIATED BY SUPEROXIDE PRODUCTION.Jacqueline D. Carter, Zhuowei Li, Lisa A. Dailey, Yuh-Chin T. Huang. CEMALB, University of North Carolina, and ORD, US EPA, Chapel Hill, North Carolina.

    Exposure to particulate matter...

  7. Inhibition of osteolysis after local administration of osthole in a TCP particles-induced osteolysis model.

    PubMed

    Lv, Shumin; Zhang, Yun; Yan, Ming; Mao, Hongjiao; Pan, Cailing; Gan, Mingxiao; Fan, Jiawen; Wang, Guoxia

    2016-07-01

    Wear debris-induced osteolysis and aseptic loosening are the most frequent late complications of total joint arthroplasty leading to revision of the prosthesis. However, no effective measures for the prevention and treatment of particles-induced osteolysis currently exist. Here, we investigated the efficacy of local administration of osthole on tricalcium phosphate (TCP) particles-induced osteolysis in a murine calvarial model. TCP particles were implanted over the calvaria of ICR mice, and established TCP particles-induced osteolysis model. On days one, four, seven, ten and thirteen post-surgery, osthole (10 mg/kg) or phosphate buffer saline (PBS) were subcutaneously injected into the calvaria of TCP particles-implanted or sham-operated mice. Two weeks later, blood, the periosteum and the calvaria were collected and processed for bone turnover markers, pro-inflammatory cytokine, histomorphometric and molecular analysis. Osthole (10 mg/kg) markedly prevented TCP particles-induced osteoclastogenesis and bone resorption in a mouse calvarial model. Osthole also inhibited the decrease of serum osteocalcin level and calvarial alkaline phosphatase (ALP) activity, and prevented the increase in the activity of tartrate resistant acid phosphatase (TRAP) and cathepsin K in the mouse calvaria. Furthermore, osthole obviously reduced the release of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) into the periosteum. Western blotting demonstrated TCP particles caused a remarkable endoplasmic reticulum (ER) stress response in the mouse calvaria, which was obviously blocked by osthole treatment. These results suggest that local administration of osthole inhibits TCP particles-induced osteolysis in the mouse calvarial in vivo, which may be mediated by inhibition of the ER stress signaling pathway, and it will be developed as a new drug in the prevention and treatment of destructive diseases caused by prosthetic wear particles.

  8. Particle-induced osteolysis in three-dimensional micro-computed tomography.

    PubMed

    Wedemeyer, Christian; Xu, Jie; Neuerburg, Carl; Landgraeber, Stefan; Malyar, Nasser M; von Knoch, Fabian; Gosheger, Georg; von Knoch, Marius; Löer, Franz; Saxler, Guido

    2007-11-01

    Small-animal models are useful for the in vivo study of particle-induced osteolysis, the most frequent cause of aseptic loosening after total joint replacement. Microstructural changes associated with particle-induced osteolysis have been extensively explored using two-dimensional (2D) techniques. However, relatively little is known regarding the 3D dynamic microstructure of particle-induced osteolysis. Therefore, we tested micro-computed tomography (micro-CT) as a novel tool for 3D analysis of wear debris-mediated osteolysis in a small-animal model of particle-induced osteolysis. The murine calvarial model based on polyethylene particles was utilized in 14 C57BL/J6 mice randomly divided into two groups. Group 1 received sham surgery, and group 2 was treated with polyethylene particles. We performed 3D micro-CT analysis and histological assessment. Various bone morphometric parameters were assessed. Regression was used to examine the relation between the results achieved by the two methods. Micro-CT analysis provides a fully automated means to quantify bone destruction in a mouse model of particle-induced osteolysis. This method revealed that the osteolytic lesions in calvaria in the experimental group were affected irregularly compared to the rather even distribution of osteolysis in the control group. This is an observation which would have been missed if histomorphometric analysis only had been performed, leading to false assessment of the actual situation. These irregularities seen by micro-CT analysis provide new insight into individual bone changes which might otherwise be overlooked by histological analysis and can be used as baseline information on which future studies can be designed.

  9. Formation of amorphous materials

    DOEpatents

    Johnson, William L.; Schwarz, Ricardo B.

    1986-01-01

    Metastable amorphous or fine crystalline materials are formed by solid state reactions by diffusion of a metallic component into a solid compound or by diffusion of a gas into an intermetallic compound. The invention can be practiced on layers of metals deposited on an amorphous substrate or by intermixing powders with nucleating seed granules. All that is required is that the diffusion of the first component into the second component be much faster than the self-diffusion of the first component. The method is practiced at a temperature below the temperature at which the amorphous phase transforms into one or more crystalline phases and near or below the temperature at which the ratio of the rate of diffusion of the first component to the rate of self-diffusion is at least 10.sup.4. This anomalous diffusion criteria is found in many binary, tertiary and higher ordered systems of alloys and appears to be found in all alloy systems that form amorphous materials by rapid quenching. The method of the invention can totally convert much larger dimensional materials to amorphous materials in practical periods of several hours or less.

  10. Structural Amorphous Steels

    NASA Astrophysics Data System (ADS)

    Lu, Z. P.; Liu, C. T.; Thompson, J. R.; Porter, W. D.

    2004-06-01

    Recent advancement in bulk metallic glasses, whose properties are usually superior to their crystalline counterparts, has stimulated great interest in fabricating bulk amorphous steels. While a great deal of effort has been devoted to this field, the fabrication of structural amorphous steels with large cross sections has remained an alchemist’s dream because of the limited glass-forming ability (GFA) of these materials. Here we report the discovery of structural amorphous steels that can be cast into glasses with large cross-section sizes using conventional drop-casting methods. These new steels showed interesting physical, magnetic, and mechanical properties, along with high thermal stability. The underlying mechanisms for the superior GFA of these materials are discussed.

  11. Self-organization of a periodic structure between amorphous and crystalline phases in a GeTe thin film induced by femtosecond laser pulse amorphization

    SciTech Connect

    Katsumata, Y.; Morita, T.; Morimoto, Y.; Shintani, T.; Saiki, T.

    2014-07-21

    A self-organized fringe pattern in a single amorphous mark of a GeTe thin film was formed by multiple femtosecond pulse amorphization. Micro Raman measurement indicates that the fringe is a periodic alternation between crystalline and amorphous phases. The period of the fringe is smaller than the irradiation wavelength and the direction is parallel to the polarization direction. Snapshot observation revealed that the fringe pattern manifests itself via a complex but coherent process, which is attributed to crystallization properties unique to a nonthermally amorphized phase and the distinct optical contrast between crystalline and amorphous phases.

  12. Amorphous silicon photovoltaic devices

    DOEpatents

    Carlson, David E.; Lin, Guang H.; Ganguly, Gautam

    2004-08-31

    This invention is a photovoltaic device comprising an intrinsic or i-layer of amorphous silicon and where the photovoltaic device is more efficient at converting light energy to electric energy at high operating temperatures than at low operating temperatures. The photovoltaic devices of this invention are suitable for use in high temperature operating environments.

  13. Disorder-induced amorphization

    SciTech Connect

    Lam, N.Q.; Okamoto, P.R.; Li, Mo

    1997-03-01

    Many crystalline materials undergo a crystalline-to-amorphous (c-a) phase transition when subjected to energetic particle irradiation at low temperatures. By focusing on the mean-square static atomic displacement as a generic measure of chemical and topological disorder, we are led quite naturally to a generalized version of the Lindemann melting criterion as a conceptual framework for a unified thermodynamic approach to solid-state amorphizing transformations. In its simplest form, the generalized Lindemann criterion assumes that the sum of the static and dynamic mean-square atomic displacements is constant along the polymorphous melting curve so that c-a transformations can be understood simply as melting of a critically-disordered crystal at temperatures below the glass transition temperature where the supercooled liquid can persist indefinitely in a configurationally-frozen state. Evidence in support of the generalized Lindemann melting criterion for amorphization is provided by a large variety of experimental observations and by molecular dynamics simulations of heat-induced melting and of defect-induced amorphization of intermetallic compounds.

  14. Amorphous semiconductor solar cell

    DOEpatents

    Dalal, Vikram L.

    1981-01-01

    A solar cell comprising a back electrical contact, amorphous silicon semiconductor base and junction layers and a top electrical contact includes in its manufacture the step of heat treating the physical junction between the base layer and junction layer to diffuse the dopant species at the physical junction into the base layer.

  15. Influence of resistivity on energetic trapped particle-induced internal kink modes

    SciTech Connect

    Biglari, H.; Chen, L.

    1986-06-01

    The influence of resistivity on energetic trapped particle-induced internal kink modes, dubbed ''fishbones'' in the literature, is explored. A general dispersion relation, which recovers the ideal theory in its appropriate limit, is derived and analyzed. An important implication of the theory for present generation fusion devices such as the Joint European Torus (Plasma Physics and Controlled Nuclear Fusion Research (IAEA, London, 1984), Vol I, p.11) is that they will be stable to fishbone activity.

  16. Dendritic cells enhance UHMWPE wear particle-induced osteoclast differentiation of macrophages.

    PubMed

    Cang, Dingwei; Guo, Kaijin; Zhao, Fengchao

    2015-10-01

    Ultra-high molecular weight polyethylene (UHMWPE) has been widely used in large joint replacement. Osteolysis induced by the UHMWPE wear particles is one of the main causes of replacement failure. This study aims to elucidate whether dendritic cells play a role in UHMWPE particle-induced osteolysis. An in vitro Raw 264.7 and DC 2.4 coculture system was employed to examine the effects of dendritic cells on the inflammatory and osteoclastogenic responses of Raw 264.7 toward UHMWPE particles. The expression of cytokines, NF-κB, and osteoclast marker genes was analyzed by ELISA, western blot, or quantitative PCR. The osteoclast differentiation was measured by TRAP staining and flow cytometry. UHMWPE particles induced Raw 264.7 cells to differentiate into osteoclasts, which was enhanced by coculturing with DC 2.4 cells. DC 2.4 cells augmented UHMWPE particle-elicited activation of NF-κB signaling, higher levels of TNF-α and MCP-1, and an increased expression of MMP-9, Calcr, and Ctsk, though DC 2.4 coculture alone did not significantly cause the aforementioned changes. These results suggest that dendritic cells, among other immune cells recruited by UHMWPE particle induced inflammation, could further exacerbate inflammation and osteolysis.

  17. Amorphous metallic foam

    NASA Astrophysics Data System (ADS)

    Schroers, Jan; Veazey, Chris; Johnson, William L.

    2003-01-01

    The bulk glass forming alloy Pd43Ni10Cu27P20 is processed into a low-density amorphous metallic foam. Pd43Ni10Cu27P20 is mixed with hydrated B2O3, which releases gas at elevated temperature and/or low pressure. Very homogeneous foams are achieved due to the high viscosity of the alloy even at its liquidus temperature. By processing at the liquidus temperature and decreasing the pressure to 10-2 mbar, well-distributed bubbles expand to foam the material. Foam densities as low as 1.4×103 kg/m3 were obtained, corresponding to a bubble volume fraction of 84%. The bubble diameter ranges between 2×10-4 and 1×10-3 m. Thermal analysis by differential scanning calorimetry confirms the amorphous nature of the foam. Furthermore, it reveals that the foam's thermal stability is comparable to the bulk material.

  18. Amorphous silicon radiation detectors

    DOEpatents

    Street, Robert A.; Perez-Mendez, Victor; Kaplan, Selig N.

    1992-01-01

    Hydrogenated amorphous silicon radiation detector devices having enhanced signal are disclosed. Specifically provided are transversely oriented electrode layers and layered detector configurations of amorphous silicon, the structure of which allow high electric fields upon application of a bias thereby beneficially resulting in a reduction in noise from contact injection and an increase in signal including avalanche multiplication and gain of the signal produced by incoming high energy radiation. These enhanced radiation sensitive devices can be used as measuring and detection means for visible light, low energy photons and high energy ionizing particles such as electrons, x-rays, alpha particles, beta particles and gamma radiation. Particular utility of the device is disclosed for precision powder crystallography and biological identification.

  19. Amorphous silicon radiation detectors

    DOEpatents

    Street, R.A.; Perez-Mendez, V.; Kaplan, S.N.

    1992-11-17

    Hydrogenated amorphous silicon radiation detector devices having enhanced signal are disclosed. Specifically provided are transversely oriented electrode layers and layered detector configurations of amorphous silicon, the structure of which allow high electric fields upon application of a bias thereby beneficially resulting in a reduction in noise from contact injection and an increase in signal including avalanche multiplication and gain of the signal produced by incoming high energy radiation. These enhanced radiation sensitive devices can be used as measuring and detection means for visible light, low energy photons and high energy ionizing particles such as electrons, x-rays, alpha particles, beta particles and gamma radiation. Particular utility of the device is disclosed for precision powder crystallography and biological identification. 13 figs.

  20. Defects in Amorphous Metals.

    DTIC Science & Technology

    1982-07-01

    this map with a similar plot of the experimental data. An experimental deformation data map for Pd-based amorphous al- loys is shown in fig. 10. In the...Masumoto. I Mat. Sci. 12 (1977) 1927, [IgI T M Ha.es. J. W Allen. J. Tauc . B. C. Giessen and J. J. Hauser. Phys. Re. Lett. 41 i197s) 1282 [191 J

  1. Nano-Crystalline Li1.2Mn0.6Ni0.2O₂ Prepared via Amorphous Complex Precursor and Its Electrochemical Performances as Cathode Material for Lithium-Ion Batteries.

    PubMed

    He, Xiangming; Wang, Jixian; Wang, Li; Li, Jianjun

    2016-08-05

    An amorphous complex precursor with uniform Mn/Ni cation distribution is attempted for preparing a nano-structured layered Li-rich oxide (Li1.2Mn0.6Ni0.2O₂)cathode material, using diethylenetriaminepentaacetic acid (DTPA) as a chelating agent. The materials are characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical tests. The crystal structure of Li-rich materials is found to be closely related to synthesis temperature. As-obtained nano materials sintered at 850 °C for 10 h show an average size of 200 nm with a single crystal phase and good crystallinity. At a current density of 20 mA·g(-1), the specific discharge capacity reaches 221 mAh·g(-1) for the first cycle and the capacity retention is 81% over 50 cycles. Even at a current density of 1000 mA·g(-1), the capacity is as high as 118 mAh·g(-1). The enhanced rate capability can be ascribed to the nano-sized morphology and good crystal structure.

  2. Infrared emission from hydrogenated amorphous carbon and amorphous carbon grains in the interstellar medium

    NASA Technical Reports Server (NTRS)

    Duley, W. W.; Jones, A. P.; Taylor, S. D.; Williams, D. A.

    1993-01-01

    The correlations deduced by Boulanger et al. (1990) from IRAS maps of the Chamaeleon, Taurus and Ursa Major molecular cloud complexes are interpreted in terms of the evolutionary hydrogenated amorphous carbon model of interstellar dust. In particular, regions of relatively strong 12-micron emission may be regions where recently accreted carbon is being converted by ambient UV to small PAHs in situ. Regions of weak 12-micron emission are probably quiescent regions where carbon has been annealed to amorphous carbon. Observational consequences of these inferences are briefly described.

  3. Structural studies of several distinct metastable forms of amorphous ice.

    PubMed

    Tulk, C A; Benmore, C J; Urquidi, J; Klug, D D; Neuefeind, J; Tomberli, B; Egelstaff, P A

    2002-08-23

    Structural changes during annealing of high-density amorphous ice were studied with both neutron and x-ray diffraction. The first diffraction peak was followed from the high- to the low-density amorphous form. Changes were observed to occur through a series of intermediate forms that appear to be metastable at each anneal temperature. Five distinct amorphous forms were studied with neutron scattering, and many more forms may be possible. Radial distribution functions indicate that the structure evolves systematically between 4 and 8 angstroms. The phase transformations in low-temperature liquid water may be much more complex than currently understood.

  4. Strontium inhibits titanium particle-induced osteoclast activation and chronic inflammation via suppression of NF-κB pathway

    PubMed Central

    Zhu, Shijun; Hu, Xuanyang; Tao, Yunxia; Ping, Zichuan; Wang, Liangliang; Shi, Jiawei; Wu, Xiexing; Zhang, Wen; Yang, Huilin; Nie, Zhikui; Xu, Yaozeng; Wang, Zhirong; Geng, Dechun

    2016-01-01

    Wear-particle-induced chronic inflammation and osteoclastogenesis have been identified as critical factors of aseptic loosening. Although strontium is known to be involved in osteoclast differentiation, its effect on particle-induced inflammatory osteolysis remains unclear. In this study, we investigate the potential impact and underling mechanism of strontium on particle-induced osteoclast activation and chronic inflammation in vivo and in vitro. As expected, strontium significantly inhibited titanium particle-induced inflammatory infiltration and prevented bone loss in a murine calvarial osteolysis model. Interestingly, the number of mature osteoclasts decreased after treatment with strontium in vivo, suggesting osteoclast formation might be inhibited by strontium. Additionally, low receptor activator of nuclear factor-κB ligand (RANKL), tumor necrosis factor-α, interleukin-1β, interleukin-6 and p65 immunochemistry staining were observed in strontium-treatment groups. In vitro, strontium obviously decreased osteoclast formation, osteoclastogenesis-related gene expression, osteoclastic bone resorption and pro-inflammatory cytokine expression in bone-marrow-derived macrophages in a dose-dependent manner. Furthermore, we demonstrated that strontium impaired osteoclastogenesis by blocking RANKL-induced activation of NF-κB pathway. In conclusion, our study demonstrated that strontium can significantly inhibit particle-induced osteoclast activation and inflammatory bone loss by disturbing the NF-κB pathway, and is an effective therapeutic agent for the treatment of wear particle-induced aseptic loosening. PMID:27796351

  5. Solid state amorphization kinetic of alpha lactose upon mechanical milling.

    PubMed

    Caron, Vincent; Willart, Jean-François; Lefort, Ronan; Derollez, Patrick; Danède, Florence; Descamps, Marc

    2011-11-29

    It has been previously reported that α-lactose could be totally amorphized by ball milling. In this paper we report a detailed investigation of the structural and microstructural changes by which this solid state amorphization takes place. The investigations have been performed by Powder X-ray Diffraction, Solid State Nuclear Magnetic Resonance ((13)C CP-MAS) and Differential Scanning Calorimetry. The results reveal the structural complexity of the material in the course of its amorphization so that it cannot be considered as a simple mixture made of a decreasing crystalline fraction and an increasing amorphous fraction. Heating this complexity can give rise to a fully nano-crystalline material. The results also show that chemical degradations upon heating are strongly connected to the melting process.

  6. Protection against fine particle-induced pulmonary and systemic inflammation by omega-3 polyunsaturated fatty acids.

    PubMed

    Li, Xiang-Yong; Hao, Lei; Liu, Ying-Hua; Chen, Chih-Yu; Pai, Victor J; Kang, Jing X

    2017-03-01

    Exposure to fine particulate matter, such as through air pollution, has been linked to the increased incidence of chronic diseases. However, few measures have been taken to reduce the health risks associated with fine particle exposure. The identification of safe and effective methods to protect against fine particle exposure-related damage is urgently needed. We used synthetic, non-toxic, fluorescent fine particles to investigate the physical distribution of inhaled fine particles and their effects on pulmonary and systemic inflammation in mice. Tissue levels of omega-3 fatty acids were elevated via dietary supplementation or the fat-1 transgenic mouse model. Markers of pulmonary and systemic inflammation were assessed. We discovered that fine particulate matter not only accumulates in the lungs but can also penetrate the pulmonary barrier and travel into other organs, including the brain, liver, spleen, kidney, and testis. These particles induced both pulmonary and systemic inflammation and increased oxidative stress. We also show that elevating tissue levels of omega-3 fatty acids was effective in reducing fine particle-induced inflammation, whether as a preventive method (prior to exposure) or as an intervention (after exposure). These results advance our understanding of how fine particles contribute to disease development and suggest that increasing tissue omega-3 levels may be a promising nutritional means for reducing the risk of diseases induced by particle exposure. Our findings demonstrate that elevating tissue omega-3 levels can prevent and treat fine particle-induced health problems and thereby present an immediate, practical solution for reducing the disease burden of air pollution. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  7. Local effect of IL-4 delivery on polyethylene particle induced osteolysis in the murine calvarium

    PubMed Central

    Rao, Allison J.; Nich, Christophe; Dhulipala, Lakshmi S.; Gibon, Emmanuel; Valladares, Roberto; Zwingenberger, Stefan; Smith, R. Lane; Goodman, Stuart B.

    2014-01-01

    Wear particles generated with use of total joint replacements incite a chronic macrophage-mediated inflammatory reaction, which leads to implant failure. Macrophage activation may be polarized into two states, with an M1 proinflammatory state dominating an alternatively activated M2 anti-inflammatory state. We hypothesized that IL-4, an activator of M2 macrophages, could modulate polyethylene (PE) particle-induced osteolysis in an experimental murine model. Four animal groups included (a) calvarial saline injection with harvest at 14 days (b) single calvarial injection of PE particles subcutaneously (SC) without IL-4 (c) PE particles placed as in (b), then IL-4 given SC for 14 consecutive days and (d) PE particles as in (b) then IL-4 beginning 7 days after particle injection for 7 days. The calvarial bone volume to total tissue volume was measured using microCT and histomorphometry. Calvaria were cultured for 24 h to assess release of RANKL, OPG, TNF-α, and IL-1ra and isolation and identification of M1 and M2 specific proteins. MicroCT and histomorphometric analysis showed that bone loss was significantly decreased following IL-4 administration to PE treated calvaria for both 7 and 14 days. Western blot analysis showed an increased M1/M2 ratio in the PE treated calvaria, which decreased with addition of IL-4. Cytokine analysis showed that the RANKL/OPG ratio and TNF-α/IL-1ra ratio decreased in PE-treated calvaria following IL-4 addition for 14 days. IL-4 delivery mitigated PE particle-induced osteolysis through macrophage polarization. Modulation of macrophage polarization is a potential treatment strategy for wear particle induced periprosthetic osteolysis. PMID:23225668

  8. Curcumin Attenuates Titanium Particle-Induced Inflammation by Regulating Macrophage Polarization In Vitro and In Vivo

    PubMed Central

    Li, Bin; Hu, Yan; Zhao, Yaochao; Cheng, Mengqi; Qin, Hui; Cheng, Tao; Wang, Qiaojie; Peng, Xiaochun; Zhang, Xianlong

    2017-01-01

    Periprosthetic inflammatory osteolysis and subsequent aseptic loosening are commonly observed in total joint arthroplasty. Other than revision surgery, few approved treatments are available for this complication. Wear particle-induced inflammation and macrophage polarization state play critical roles in periprosthetic osteolysis. We investigated the effects of curcumin, a polyphenol extracted from Curcuma longa, on titanium (Ti) particle-induced inflammation and macrophage polarization in vitro using the murine cell line RAW 264.7 and in vivo using a murine air pouch model. The expression of specific macrophage markers was qualitatively analyzed by immunofluorescence (inducible nitric oxide synthase and CD206) and quantitatively analyzed by flow cytometry (CCR7 and CD206), representing M1 and M2 macrophages, respectively. Our results show that curcumin induced a higher percentage of M2 macrophages together with a higher concentration of anti-inflammatory cytokine IL-10, and a lower percentage of M1 macrophages with a lower concentration of pro-inflammatory cytokines (TNF-α and IL-6). The genes encoding CD86 (M1) and CD163 (M2), two additional markers, were shifted by curcumin toward an M2 phenotype. C57BL/J6 mice were injected with air and Ti particles to establish an air pouch model. Curcumin reduced cell infiltration in the pouch membrane and decreased membrane thickness. The analysis of exudates obtained from pouches demonstrated that the effects of curcumin on macrophage polarization and cytokine production were similar to those observed in vitro. These results prove that curcumin suppresses Ti particle-induced inflammation by regulating macrophage polarization. Thus, curcumin could be developed as a new therapeutic candidate for the prevention and treatment of inflammatory osteolysis and aseptic loosening. PMID:28197150

  9. Curcumin Attenuates Titanium Particle-Induced Inflammation by Regulating Macrophage Polarization In Vitro and In Vivo.

    PubMed

    Li, Bin; Hu, Yan; Zhao, Yaochao; Cheng, Mengqi; Qin, Hui; Cheng, Tao; Wang, Qiaojie; Peng, Xiaochun; Zhang, Xianlong

    2017-01-01

    Periprosthetic inflammatory osteolysis and subsequent aseptic loosening are commonly observed in total joint arthroplasty. Other than revision surgery, few approved treatments are available for this complication. Wear particle-induced inflammation and macrophage polarization state play critical roles in periprosthetic osteolysis. We investigated the effects of curcumin, a polyphenol extracted from Curcuma longa, on titanium (Ti) particle-induced inflammation and macrophage polarization in vitro using the murine cell line RAW 264.7 and in vivo using a murine air pouch model. The expression of specific macrophage markers was qualitatively analyzed by immunofluorescence (inducible nitric oxide synthase and CD206) and quantitatively analyzed by flow cytometry (CCR7 and CD206), representing M1 and M2 macrophages, respectively. Our results show that curcumin induced a higher percentage of M2 macrophages together with a higher concentration of anti-inflammatory cytokine IL-10, and a lower percentage of M1 macrophages with a lower concentration of pro-inflammatory cytokines (TNF-α and IL-6). The genes encoding CD86 (M1) and CD163 (M2), two additional markers, were shifted by curcumin toward an M2 phenotype. C57BL/J6 mice were injected with air and Ti particles to establish an air pouch model. Curcumin reduced cell infiltration in the pouch membrane and decreased membrane thickness. The analysis of exudates obtained from pouches demonstrated that the effects of curcumin on macrophage polarization and cytokine production were similar to those observed in vitro. These results prove that curcumin suppresses Ti particle-induced inflammation by regulating macrophage polarization. Thus, curcumin could be developed as a new therapeutic candidate for the prevention and treatment of inflammatory osteolysis and aseptic loosening.

  10. The Stabilization of Amorphous Zopiclone in an Amorphous Solid Dispersion.

    PubMed

    Milne, Marnus; Liebenberg, Wilna; Aucamp, Marique

    2015-10-01

    Zopiclone is a poorly soluble psychotherapeutic agent. The aim of this study was to prepare and characterize an amorphous form of zopiclone as well as the characterization and performance of a stable amorphous solid dispersion. The amorphous form was prepared by the well-known method of quench-cooling of the melt. The solid dispersion was prepared by a solvent evaporation method of zopiclone, polyvinylpyrrolidone-25 (PVP-25), and methanol, followed by freeze-drying. The physico-chemical properties and stability of amorphous zopiclone and the solid dispersion was studied using differential scanning calorimetry (DSC), infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), hot-stage microscopy (HSM), X-ray diffractometry (XRD), solubility, and dissolution studies. The zopiclone amorphous solid-state form was determined to be a fragile glass; it was concluded that the stability of the amorphous form is influenced by both temperature and water. Exposure of amorphous zopiclone to moisture results in rapid transformation of the amorphous form to the crystalline dihydrated form. In comparison, the amorphous solid dispersion proved to be more stable with increased aqueous solubility.

  11. SIRT1 protects osteoblasts against particle-induced inflammatory responses and apoptosis in aseptic prosthesis loosening.

    PubMed

    Deng, Zhantao; Wang, Zhenheng; Jin, Jiewen; Wang, Yong; Bao, Nirong; Gao, Qian; Zhao, Jianning

    2017-02-01

    We hypothesized that SIRT1 downregulation in osteoblasts induced by wear particles was one of the reasons for particle-induced osteolysis (PIO) in total joint arthroplasty failure. In the present study, the expression of SIRT1 was examined in osteoblasts treated with TiAl6V4 particles (TiPs) and CoCrMo particles (CoPs) from materials used in prosthetics and specimens from PIO animal models. To address whether SIRT1 downregulation triggers inflammatory responses and apoptosis in osteoblasts, the effect of a SIRT1 activator, resveratrol on the expression of inflammatory cytokines and apoptosis in particle-treated osteoblasts was tested. The results demonstrated that SIRT1 expression was significantly downregulated in particle-treated osteoblasts and PIO animal models. Both pharmacological activation and overexpression of SIRT1 dramatically reduced the particle-induced expression of inflammatory cytokines and osteoblast apoptosis through NF-κB and p53 signaling, respectively. Furthermore, in PIO animal models, resveratrol significantly reduced the severity of osteolysis. Collectively, the results of the present study indicated that SIRT1 plays a vital role in the pathogenesis of aseptic loosening, and further treatment targeted at SIRT1 possibly lead to novel approaches for prevention of aseptic prosthesis loosening. Aseptic loosening is the most common cause of total hip arthroplasty (THA) and total knee arthroplasty (TKA) failure and revision surgery. However, there is still no effective therapeutic target in the clinical treatment. Besides, the underlying mechanism of aseptic loosening is largely unknown. The result of our study indicated that SIRT1 has the ability to effectively regulate the wear particle-induced inflammatory responses, apoptosis, osteolysis in particle-stimulated osteoblasts and particle-induced osteolysis animal models. Our study provides a potential target for the prevention and treatment of aseptic loosening and further investigated the

  12. Anomalous effect of trench-oxide depth on alpha-particle-induced charge collection

    SciTech Connect

    Shin, H.; Kim, N.M.

    1999-06-01

    The effect of trench-oxide depth on the alpha-particle-induced charge collection is analyzed for the first time. From the simulation results, it was found that the depth of trench oxide has a considerable influence on the amount of collected charge. The confining of generated charge by the trench oxide was identified as a cause of this anomalous effect. Therefore, the tradeoff between soft error rate and cell to cell isolation characteristics should be considered in optimizing the depth of trench oxide.

  13. Experimental Study of the Cross Sections of {alpha}-Particle Induced Reactions on 209Bi

    SciTech Connect

    Hermanne, A.; Tarkanyi, F.; Takacs, S.; Szucs, Z.

    2005-05-24

    Alpha particle induced reactions for generation of 211At used in therapeutic nuclear medicine and possible contaminants were investigated with the stacked foil activation technique on natural bismuth targets up to E{alpha}=39 MeV. Excitation functions for the reactions 209Bi({alpha},2n)211At, 209Bi({alpha},3n)210At, 209Bi({alpha},x) 210Po obtained from direct alpha emission measurements and gamma spectra from decay products are compared with earlier literature values. Thick target yields have been deduced from the experimental cross sections.

  14. CHANG'E-3 Active Particle-induced X-ray Spectrometer: ground verification test

    NASA Astrophysics Data System (ADS)

    Guo, Dongya; Peng, Wenxi; Cui, XingZhu; Wang, Huanyu

    The Active Particle-induced X-ray Spectrometer (APXS) is one of the payloads of Chang’E-3 rover Yutu, with which the major elemental composition of lunar soils and rocks can be measured on site. In order to assess the instrument performance and the accuracy of determination, ground verification test was carried out with two blind samples(basaltic rock, powder). Details of the experiments and data analysis method are discussed. The results show that the accuracy of quantitative analysis for major elements(Mg,Al,Si,K,Ca,Ti,Fe) is better than 15%.

  15. Experimental Study of the Cross Sections of α-Particle Induced Reactions on 209Bi

    NASA Astrophysics Data System (ADS)

    Hermanne, A.; Tárkányi, F.; Takács, S.; Szúcs, Z.

    2005-05-01

    Alpha particle induced reactions for generation of 211At used in therapeutic nuclear medicine and possible contaminants were investigated with the stacked foil activation technique on natural bismuth targets up to Eα=39 MeV. Excitation functions for the reactions 209Bi(α,2n)211At, 209Bi(α,3n)210At, 209Bi(α,x) 210Po obtained from direct alpha emission measurements and gamma spectra from decay products are compared with earlier literature values. Thick target yields have been deduced from the experimental cross sections.

  16. Particle induced gamma and X-ray emission spectroscopies of lithium based alloy coatings

    NASA Astrophysics Data System (ADS)

    Laird, Jamie S.; Hughes, Anthony E.; Ryan, Chris G.; Visser, P.; Terryn, H.; Mol, J. M. C.

    2017-08-01

    Lithium based inhibitors in aerospace coatings are seen as excellent replacements for their chromium counterparts which are both carcinogenic and heavier. However, Li is generally difficult to detect and following changes in its distribution due to corrosion is impossible with many standard techniques. Combining MeV Particle Induced Gamma and X-ray emission provides a powerful tool and in this paper we summarise some recent experiments on such coatings using the CSIRO Nuclear Microprobe. PIGE mapping of the LiCO3 particles and their patterning illustrates how the method will be extremely useful in monitoring surface corrosion.

  17. Broadband Ultrahigh-Resolution Spectroscopy of Particle-Induced X Rays: Extending the Limits of Nondestructive Analysis

    NASA Astrophysics Data System (ADS)

    Palosaari, M. R. J.; Käyhkö, M.; Kinnunen, K. M.; Laitinen, M.; Julin, J.; Malm, J.; Sajavaara, T.; Doriese, W. B.; Fowler, J.; Reintsema, C.; Swetz, D.; Schmidt, D.; Ullom, J. N.; Maasilta, I. J.

    2016-08-01

    Nondestructive analysis (NDA) based on x-ray emission is widely used, for example, in the semiconductor and concrete industries. Here, we demonstrate significant quantitative and qualitative improvements in broadband x-ray NDA by combining particle-induced emission with detection based on superconducting microcalorimeter arrays. We show that the technique offers great promise in the elemental analysis of thin-film and bulk samples, especially in the difficult cases where tens of different elements with nearly overlapping emission lines have to be identified down to trace concentrations. We demonstrate the efficiency and resolving capabilities by spectroscopy of several complex multielement samples in the energy range 1-10 keV, some of which have a trace amount of impurities not detectable with standard silicon drift detectors. The ability to distinguish the chemical environment of an element is also demonstrated by measuring the intensity differences and chemical shifts of the characteristics x-ray peaks of titanium compounds. In particular, we report measurements of the K α /K β intensity ratio of thin films of TiN and measurements of Ti K α satellite peak intensities in various Ti thin-film compounds. We also assess the detection limits of the technique, comment on detection limits possible in the future, and discuss possible applications.

  18. Synthesis of quenchable amorphous diamond

    DOE PAGES

    Zeng, Zhidan; Yang, Liuxiang; Zeng, Qiaoshi; ...

    2017-08-22

    Diamond owes its unique mechanical, thermal, optical, electrical, chemical, and biocompatible materials properties to its complete sp3-carbon network bonding. Crystallinity is another major controlling factor for materials properties. Although other Group-14 elements silicon and germanium have complementary crystalline and amorphous forms consisting of purely sp3 bonds, purely sp3-bonded tetrahedral amorphous carbon has not yet been obtained. In this letter, we combine high pressure and in situ laser heating techniques to convert glassy carbon into “quenchable amorphous diamond”, and recover it to ambient conditions. Our X-ray diffraction, high-resolution transmission electron microscopy and electron energy-loss spectroscopy experiments on the recovered sample andmore » computer simulations confirm its tetrahedral amorphous structure and complete sp3 bonding. This transparent quenchable amorphous diamond has, to our knowledge, the highest density among amorphous carbon materials, and shows incompressibility comparable to crystalline diamond.« less

  19. Functionalized Amorphous Aluminosilicates

    NASA Astrophysics Data System (ADS)

    Mesgar, Milad

    Alkali treated aluminosilicate (geopolymer) was functionalized by surfactant to increase the hydrophobicity for making Pickering emulsion for the first part of this work. In the first part of this study, alkali treated metakaolin was functionalized with cetyltrimethylammonium bromide ((C16H33)N(CH 3)3Br, CTAB). The electrostatic interaction between this quaternary ammonium and the surface of the aluminosilicate which has negative charge has taken place. The particles then were used to prepare Pickering emulsion. The resulting stable dispersions, obtained very fast at very simple conditions with low ratio of aluminosilicate to liquid phase. In the second part, the interaction between geopolymer and glycerol was studied to see the covalent grafting of the geopolymer for making geopolymer composite. The composite material would be the basis material to be used as support catalyst, thin coating reagent and flame retardant material and so on, Variety of techniques, Thermogravimetric (TGA), Particle-induced X-ray emission (PIXE), FTIR, Solid state NMR, Powder X-ray diffraction (PXRD), BET surface area, Elemental analysis (CHN), TEM, SEM and Optical microscopy were used to characterize the functionalized geopolymer.

  20. Hydrogenated Amorphous Silicon

    NASA Astrophysics Data System (ADS)

    Street, R. A.

    1991-08-01

    Divided roughly into two parts, the book describes the physical properties and device applications of hydrogenated amorphous silicon. The first section is concerned with the atomic and electronic structure, and covers growth defects and doping and defect reactions. The emphasis is on the optical and electronic properties that result from the disordered structure. The second part of the book describes electronic conduction, recombination, interfaces, and multilayers. The special attribute of a-Si:H which makes it useful is the ability to deposit the material inexpensively over large areas, while retaining good semiconducting properties, and the final chapter discusses various applications and devices.

  1. Particle-Induced X-Ray Emission Analysis of Atmospheric Aerosols

    NASA Astrophysics Data System (ADS)

    Gleason, Colin; Harrington, Charles; Schuff, Katie; Battaglia, Maria; Moore, Robert; Turley, Colin; Vineyard, Michael; Labrake, Scott

    2010-11-01

    We are developing a research program in ion-beam analysis (IBA) of atmospheric aerosols at the Union College Ion-Beam Analysis Laboratory to study the transport, transformation, and effects of airborne pollution in Upstate New York. The simultaneous applications of the IBA techniques of particle-induced X-ray emission (PIXE), Rutherford back-scattering spectrometry (RBS), particle-induced gamma-ray emission (PIGE), and proton elastic scattering analysis (PESA) is a powerful tool for the study of airborne pollution because they are non-destructive and provide quantitative information on nearly all elements of the periodic table. PIXE is the main IBA technique because it is able to detect nearly all elements from Na to U with high sensitivities and low detection limits. The aerosol samples are collected with cascade impactors that allow for the study of particulate matter as a function of particle size and the samples are analyzed using proton beams with energies around 2 MeV from the Union College 1.1-MV Pelletron Accelerator. The emitted X-rays are measured using a silicon drift detector with a resolution of 136 eV. We will describe how the aerosol samples were collected, discuss the PIXE analysis, and present preliminary results.

  2. Investigation of the α-particle induced nuclear reactions on natural molybdenum

    NASA Astrophysics Data System (ADS)

    Ditrói, F.; Hermanne, A.; Tárkányi, F.; Takács, S.; Ignatyuk, A. V.

    2012-08-01

    Cross-sections of alpha particle induced nuclear reactions on natural molybdenum have been studied in the frame of a systematic investigation of charged particle induced nuclear reactions on metals for different applications. The excitation functions of 93mTc, 93gTc(m+), 94mTc, 94gTc, 95mTc, 95gTc, 96gTc(m+), 99mTc, 93mMo, 99Mo(cum), 90Nb(m+), 94Ru, 95Ru,97Ru, 103Ru and 88Zr were measured up to 40 MeV alpha energy by using a stacked foil technique and activation method. The main goals of this work were to get experimental data for accelerator technology, for monitoring of alpha beam, for thin layer activation technique and for testing nuclear reaction theories. The experimental data were compared with critically analyzed published data and with the results of model calculations, obtained by using the ALICE-IPPE, EMPIRE and TALYS codes (TENDL-2011).

  3. Polyethylene and titanium particles induce osteolysis by similar, lymphocyte-independent, mechanisms.

    PubMed

    Taki, Naoya; Tatro, Joscelyn M; Nalepka, Jennifer L; Togawa, Daisuke; Goldberg, Victor M; Rimnac, Clare M; Greenfield, Edward M

    2005-03-01

    Periprosthetic osteolysis is a major clinical problem that limits the long-term survival of total joint arthroplasties. Osteolysis is induced by implant-derived wear particles, primarily from the polyethylene bearing surfaces. This study examined two hypotheses. First, that similar mechanisms are responsible for osteolysis induced by polyethylene and titanium particles. Second, that lymphocytes do not play a major role in particle-induced osteolysis. To test these hypotheses, we used the murine calvarial model that we have previously used to examine titanium-induced osteolysis. Polyethylene particles rapidly induced osteolysis in the murine calvaria 5-7 days after implantation. The polyethylene-induced osteolysis was associated with large numbers of osteoclasts as well as the formation of a thick periosteal fibrous tissue layer with numerous macrophages containing phagocytosed polyethylene particles. Polyethylene-induced osteolysis was rapidly repaired and was undetectable by day 21 after implantation. Lymphocytes were noted in the fibrous layer of wild-type mice. However, the amount of osteolysis and cytokine production induced by polyethylene particles was not substantially affected by the lack of lymphocytes in Pfp/Rag2 double knock out mice. All of these findings are similar to our observations of osteolysis induced by titanium particles. These results provide strong support for both of our hypotheses: that similar mechanisms are responsible for osteolysis induced by polyethylene and titanium particles and that lymphocytes do not play a major role in particle-induced osteolysis.

  4. Therapeutic effects of OP-1 on metal wear particle induced osteoblasts injury in vitro.

    PubMed

    Sun, Guojing; Chen, Jianmin; Yang, Shufeng; Parker, Thomas Mn; Goodman, Gary Mp; Hasama, Jack M; Zhao, Jianning

    2015-01-01

    Aseptic lossening is a main reason for the revision of total joint arthroplasty. Metal-wear particles induced deregulation of bone resorption or formation has been considered as the major process of aseptic lossening. Osteogenic protein-1 (OP-1) can be used to improve bone formation. However, such effect is not clearly understood after the metal-wear particles injury. Here, we investigated the molecular mechanisms by which OP-1 regulates the activity of bone formation and anti-inflammatory after injury. Results showed that OP-1 increased cell viability and bone formation ability of impaired osteoblast cells at 72 hours after being injured by cobalt particles. Pathway analyses revealed that both mRNA and protein levels of Smad1 and Smad5 were significantly increased upon the treatment of OP-1 in the cell injury model. Similarly, runt-related transcription factor 2 (Runx2) was also significantly upregulated in the OP-1 treated cells. Moreover, treatment with OP-1 inhibited the secretion of interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-α), and IL-18 in cobalt impaired cells. Collectively, these results suggest that OP-1 could inhibit cobalt particles induced cell injury by activating Smad1, Smad5, and Runx2, and such procedure is accompanied by anti-inflammatory reaction.

  5. Geraniin suppresses RANKL-induced osteoclastogenesis in vitro and ameliorates wear particle-induced osteolysis in mouse model

    SciTech Connect

    Xiao, Fei; Zhai, Zanjing; Jiang, Chuan; Liu, Xuqiang; Li, Haowei; Qu, Xinhua; Ouyang, Zhengxiao; Fan, Qiming; Tang, Tingting; Qin, An; Gu, Dongyun

    2015-01-01

    Wear particle-induced osteolysis and subsequent aseptic loosening remains the most common complication that limits the longevity of prostheses. Wear particle-induced osteoclastogenesis is known to be responsible for extensive bone erosion that leads to prosthesis failure. Thus, inhibition of osteoclastic bone resorption may serve as a therapeutic strategy for the treatment of wear particle induced osteolysis. In this study, we demonstrated for the first time that geraniin, an active natural compound derived from Geranium thunbergii, ameliorated particle-induced osteolysis in a Ti particle-induced mouse calvaria model in vivo. We also investigated the mechanism by which geraniin exerts inhibitory effects on osteoclasts. Geraniin inhibited RANKL-induced osteoclastogenesis in a dose-dependent manner, evidenced by reduced osteoclast formation and suppressed osteoclast specific gene expression. Specially, geraniin inhibited actin ring formation and bone resorption in vitro. Further molecular investigation demonstrated geraniin impaired osteoclast differentiation via the inhibition of the RANKL-induced NF-κB and ERK signaling pathways, as well as suppressed the expression of key osteoclast transcriptional factors NFATc1 and c-Fos. Collectively, our data suggested that geraniin exerts inhibitory effects on osteoclast differentiation in vitro and suppresses Ti particle-induced osteolysis in vivo. Geraniin is therefore a potential natural compound for the treatment of wear particle induced osteolysis in prostheses failure. - Highlights: • Geraniin suppresses osteoclasts formation and function in vitro. • Geraniin impairs RANKL-induced nuclear factor-κB and ERK signaling pathway. • Geraniin suppresses osteolysis in vivo. • Geraniin may be used for treating osteoclast related diseases.

  6. Compensated amorphous silicon solar cell

    DOEpatents

    Carlson, David E.

    1980-01-01

    An amorphous silicon solar cell incorporates a region of intrinsic hydrogenated amorphous silicon fabricated by a glow discharge wherein said intrinsic region is compensated by P-type dopants in an amount sufficient to reduce the space charge density of said region under illumination to about zero.

  7. Amorphous silicon ionizing particle detectors

    DOEpatents

    Street, Robert A.; Mendez, Victor P.; Kaplan, Selig N.

    1988-01-01

    Amorphous silicon ionizing particle detectors having a hydrogenated amorphous silicon (a--Si:H) thin film deposited via plasma assisted chemical vapor deposition techniques are utilized to detect the presence, position and counting of high energy ionizing particles, such as electrons, x-rays, alpha particles, beta particles and gamma radiation.

  8. Amorphous silicon ionizing particle detectors

    DOEpatents

    Street, R.A.; Mendez, V.P.; Kaplan, S.N.

    1988-11-15

    Amorphous silicon ionizing particle detectors having a hydrogenated amorphous silicon (a--Si:H) thin film deposited via plasma assisted chemical vapor deposition techniques are utilized to detect the presence, position and counting of high energy ionizing particles, such as electrons, x-rays, alpha particles, beta particles and gamma radiation. 15 figs.

  9. Macromolecular prodrug of dexamethasone prevents particle-induced peri-implant osteolysis with reduced systemic side effects

    PubMed Central

    Ren, Ke; Dusad, Anand; Yuan, Fang; Yuan, Hongjiang; Purdue, P. Edward; Fehringer, Edward V.; Garvin, Kevin L.; Goldring, Steven R.; Wang, Dong

    2014-01-01

    Aseptic implant loosening related to implant wear particle-induced inflammation is the most common cause of failure after joint replacement. Modulation of the inflammatory reaction to the wear products represents a rational approach for preventing aseptic implant failure. Long-term treatment using anti-inflammatory agents, however, can be associated with significant systemic side effects due to the drugs' lack of tissue specificity. To address this issue, N-(2-hydroxypropyl) methacrylamide (HPMA) copolymer-dexamethasone conjugate (P-Dex) was developed and evaluated for prevention of wear particle-induced osteolysis and the loss of fixation in a murine prosthesis failure model. Daily administration of free dexamethasone (Dex) was able to prevent wear particle-induced osteolysis, as assessed by micro-CT and histological analysis. Remarkably, monthly P-Dex administration (dose equivalent to free Dex treatment) was equally effective as free dexamethasone, but was not associated with systemic bone loss (a major adverse side effect of glucocorticoids). The reduced systemic toxicity of P-Dex is related to preferential targeting of the sites of wear particle-induced inflammation and its subcellular sequestration and retention by local inflammatory cell populations, resulting in sustained therapeutic action. These results demonstrate the feasibility of utilizing a macromolecular prodrug with reduced systemic toxicity to prevent wear particle-induced osteolysis. PMID:24326124

  10. Compensated amorphous silicon solar cell

    DOEpatents

    Devaud, Genevieve

    1983-01-01

    An amorphous silicon solar cell including an electrically conductive substrate, a layer of glow discharge deposited hydrogenated amorphous silicon over said substrate and having regions of differing conductivity with at least one region of intrinsic hydrogenated amorphous silicon. The layer of hydrogenated amorphous silicon has opposed first and second major surfaces where the first major surface contacts the electrically conductive substrate and an electrode for electrically contacting the second major surface. The intrinsic hydrogenated amorphous silicon region is deposited in a glow discharge with an atmosphere which includes not less than about 0.02 atom percent mono-atomic boron. An improved N.I.P. solar cell is disclosed using a BF.sub.3 doped intrinsic layer.

  11. Bulk amorphous materials

    SciTech Connect

    Schwarz, R.B.; Archuleta, J.I.; Sickafus, K.E.

    1998-12-01

    This is the final report for a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this work was to develop the competency for the synthesis of novel bulk amorphous alloys. The authors researched their synthesis methods and alloy properties, including thermal stability, mechanical, and transport properties. The project also addressed the development of vanadium-spinel alloys for structural applications in hostile environments, the measurement of elastic constants and thermal expansion in single-crystal TiAl from 300 to 750 K, the measurement of elastic constants in gallium nitride, and a study of the shock-induced martensitic transformations in NiTi alloys.

  12. R-Matrix Codes for Charged-particle Induced Reactionsin the Resolved Resonance Region

    SciTech Connect

    Leeb, Helmut; Dimitriou, Paraskevi; Thompson, Ian J.

    2017-01-01

    A Consultant’s Meeting was held at the IAEA Headquarters, from 5 to 7 December 2016, to discuss the status of R-matrix codes currently used in calculations of charged-particle induced reaction cross sections at low energies. The meeting was a follow-up to the R-matrix Codes meeting held in December 2015, and served the purpose of monitoring progress in: the development of a translation code to enable exchange of input/output parameters between the various codes in different formats, fitting procedures and treatment of uncertainties, the evaluation methodology, and finally dissemination. The details of the presentations and technical discussions, as well as additional actions that were proposed to achieve all the goals of the meeting are summarized in this report.

  13. Production of medically useful bromine isotopes via alpha-particle induced nuclear reactions

    NASA Astrophysics Data System (ADS)

    Breunig, Katharina; Scholten, Bernhard; Spahn, Ingo; Hermanne, Alex; Spellerberg, Stefan; Coenen, Heinz H.; Neumaier, Bernd

    2017-09-01

    The cross sections of α-particle induced reactions on arsenic leading to the formation of 76,77,78Br were measured from their respective thresholds up to 37 MeV. Thin sediments of elemental arsenic powder were irradiated together with Al degrader and Cu monitor foils using the established stacked-foil technique. For determination of the effective α-particle energies and of the effective beam current through the stacks the cross-section ratios of the monitor nuclides 67Ga/66Ga were used. This should help resolve discrepancies in existing literature data. Comparison of the data with the available excitation functions shows some slight energy shifts as well as some differences in curve shapes. The calculated thick target yields indicate, that 77Br can be produced in the energy range Eα = 25 → 17 MeV free of isotopic impurities in quantities sufficient for medical application.

  14. Boron analysis for neutron capture therapy using particle-induced gamma-ray emission.

    PubMed

    Nakai, Kei; Yamamoto, Yohei; Okamoto, Emiko; Yamamoto, Tetsuya; Yoshida, Fumiyo; Matsumura, Akira; Yamada, Naoto; Kitamura, Akane; Koka, Masashi; Satoh, Takahiro

    2015-12-01

    The neutron source of BNCT is currently changing from reactor to accelerator, but peripheral facilities such as a dose-planning system and blood boron analysis have still not been established. To evaluate the potential application of particle-induced gamma-ray emission (PIGE) for boron measurement in clinical boron neutron capture therapy, boronophenylalanine dissolved within a cell culture medium was measured using PIGE. PIGE detected 18 μgB/mL f-BPA in the culture medium, and all measurements of any given sample were taken within 20 min. Two hours of f-BPA exposure was required to create a boron distribution image. However, even though boron remained in the cells, the boron on the cell membrane could not be distinguished from the boron in the cytoplasm. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. Alpha-particle-induced charge collection in scaled dram cells with advanced structures

    NASA Astrophysics Data System (ADS)

    Takeuchi, K.; Aoki, M.; Watanabe, Y.; Itoh, K.

    1990-11-01

    Alpha-particle-induced charge collection in scaled DRAM cells with advanced structures are experimentally examined. It is concluded that the storage charge necessary to avoid the soft-errors, QC, is proportional to the diagonal length of the depletion region in most types of scaled DRAM cells including PMOS cells. For some types of DRAM cells, however, additional effects on the QC should be considered: (a) for DRAM cells with LOCOS isolation, the collected charge enhancement caused by the charge multiplication at the LOCOS junction edge becomes prominent with scaling, (b) for substrate-plate SPC (Sheat Plate Capacitor) trench cells, the potential slope towards the surface caused by the p+ plate regions enhance the charge collection, (c) for PMOS cells, the collected charge enhancement through the charge multiplication can be weaker than that in NMOS cells.

  16. Water-soluble core/shell nanoparticles for proton therapy through particle-induced radiation

    NASA Astrophysics Data System (ADS)

    Park, Jeong Chan; Jung, Myung-Hwan; Kim, Maeng Jun; Kim, Kye-Ryung

    2015-02-01

    Metallic nanoparticles have been used in biomedical applications such as magnetic resonance imaging (MRI), therapy, and drug delivery systems. Metallic nanoparticles as therapeutic tools have been demonstrated using radio-frequency magnetic fields or near-infrared light. Recently, therapeutic applications of metallic nanomaterials combined with proton beams have been reported. Particle-induced radiation from metallic nanoparticles, which can enhance the therapeutic effects of proton therapy, was released when the nanoparticles were bombarded by a high-energy proton beam. Core/shell nanoparticles, especially Au-coated magnetic nanoparticles, have drawn attention in biological applications due to their attractive characteristics. However, studies on the phase transfer of organic-ligand-based core/shell nanoparticles into water are limited. Herein, we demonstrated that hydrophobic core/shell structured nanomaterials could be successfully dispersed in water through chloroform/surfactant mixtures. The effects of the core/shell nanomaterials and the proton irradiation on Escherichia coli (E. coli) were also explored.

  17. Development of a Reference Database for Particle-Induced Gamma-ray Emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Dimitriou, P.; Becker, H.-W.; Bogdanović-Radović, I.; Chiari, M.; Goncharov, A.; Jesus, A. P.; Kakuee, O.; Kiss, A. Z.; Lagoyannis, A.; Räisänen, J.; Strivay, D.; Zucchiatti, A.

    2016-03-01

    Particle-Induced Gamma-ray Emission (PIGE) is a powerful analytical technique that exploits the interactions of rapid charged particles with nuclei located near a sample surface to determine the composition and structure of the surface regions of solids by measurement of characteristic prompt γ rays. The potential for depth profiling of this technique has long been recognized, however, the implementation has been limited owing to insufficient knowledge of the physical data and lack of suitable user-friendly computer codes for the applications. Although a considerable body of published data exists in the nuclear physics literature for nuclear reaction cross sections with γ rays in the exit channel, there is no up-to-date, comprehensive compilation specifically dedicated to IBA applications. A number of PIGE cross-section data had already been uploaded to the Ion Beam Analysis Nuclear Data Library (IBANDL)

  18. Modeling fundamental plasma transport and particle-induced emission in a simplified Test Cell

    NASA Astrophysics Data System (ADS)

    Giuliano, Paul Nicholas

    This work involves the modeling of fundamental plasma physics processes occurring within environments that are similar to that of the discharge and plume regions of electric propulsion devices such as Hall effect thrusters. The research is conducted as a collaborative effort with the Plasma & Space Propulsion Laboratory at the University of California, Los Angeles (UCLA), as part of the University of Michigan/AFRL Center for Excellence in Electric Propulsion (MACEEP). Transport physics, such as particle-particle collisions and particle-induced electron emission, are simulated within the UCLA experimental facility and its representative electric propulsion environment. Simulation methods employed include the direct simulation Monte Carlo (DSMC) and particle-in-cell (PIC) techniques for the kinetic simulation of charged, rarefied species on high-performance computing architectures. Momentum- (MEX) and charge-exchange (CEX) collision cross-section models for Xe and Xe+, both total and differential, are successfully validated at collision energies of ˜1.5 keV within the novel facility. Heavy-species collisional transport models are validated and the importance of scattering anisotropy in this collision-dominated environment is shown. The theory of particle-induced electron emission (PIE) is then investigated in the context of the relevant energies and environments of the UCLA facility and electric propulsion devices and diagnostics. Reduced, semi-empirical models for total yield and emitted electron energy distribution functions that are easily implemented in a DSMC-PIC code are developed for the simulation of secondary-electron emission due to low-energy ions and high-energy atoms, even in the case of incomplete target-material information. These models are important for the characterization of electric propulsion devices due to the problematic nature of low-temperature plasma diagnostic techniques in which the emission of electrons is physically indistinguishable

  19. Schisantherin A suppresses osteoclast formation and wear particle-induced osteolysis via modulating RANKL signaling pathways

    SciTech Connect

    He, Yi; Zhang, Qing; Shen, Yi; Chen, Xia; Zhou, Feng; Peng, Dan

    2014-07-04

    Highlights: • Schisantherin A suppresses osteoclasts formation and function in vitro. • Schisantherin A impairs RANKL signaling pathway. • Schisantherin A suppresses osteolysis in vivo. • Schisantherin A may be used for treating osteoclast related diseases. - Abstract: Receptor activator of NF-κB ligand (RANKL) plays critical role in osteoclastogenesis. Targeting RANKL signaling pathways has been a promising strategy for treating osteoclast related bone diseases such as osteoporosis and aseptic prosthetic loosening. Schisantherin A (SA), a dibenzocyclooctadiene lignan isolated from the fruit of Schisandra sphenanthera, has been used as an antitussive, tonic, and sedative agent, but its effect on osteoclasts has been hitherto unknown. In the present study, SA was found to inhibit RANKL-induced osteoclast formation and bone resorption. The osteoclastic specific marker genes induced by RANKL including c-Src, SA inhibited OSCAR, cathepsin K and TRAP in a dose dependent manner. Further signal transduction studies revealed that SA down-regulate RANKL-induced nuclear factor-kappaB (NF-κB) signaling activation by suppressing the phosphorylation and degradation of IκBα, and subsequently preventing the NF-κB transcriptional activity. Moreover, SA also decreased the RANKL-induced MAPKs signaling pathway, including JNK and ERK1/2 posphorylation while had no obvious effects on p38 activation. Finally, SA suppressed the NF-κB and MAPKs subsequent gene expression of NFATc1 and c-Fos. In vivo studies, SA inhibited osteoclast function and exhibited bone protection effect in wear-particle-induced bone erosion model. Taken together, SA could attenuate osteoclast formation and wear particle-induced osteolysis by mediating RANKL signaling pathways. These data indicated that SA is a promising therapeutic natural compound for the treatment of osteoclast-related prosthesis loosening.

  20. Containerless processing of amorphous ceramics

    NASA Technical Reports Server (NTRS)

    Weber, J. K. Richard; Krishnan, Shankar; Schiffman, Robert A.; Nordine, Paul C.

    1990-01-01

    The absence of gravity allows containerless processing of materials which could not otherwise be processed. High melting point, hard materials such as borides, nitrides, and refractory metals are usually brittle in their crystalline form. The absence of dislocations in amorphous materials frequently endows them with flexibility and toughness. Systematic studies of the properties of many amorphous materials have not been carried out. The requirements for their production is that they can be processed in a controlled way without container interaction. Containerless processing in microgravity could permit the control necessary to produce amorphous forms of hard materials.

  1. FY06 Annual Report: Amorphous Semiconductors for Gamma Radiation Detection (ASGRAD)

    SciTech Connect

    Johnson, Bradley R.; Riley, Brian J.; Crum, Jarrod V.; Sundaram, S. K.; Henager, Charles H.; Zhang, Yanwen; Shutthanandan, V.

    2007-01-01

    We describe progress in the development of new materials for portable, room-temperature, gamma-radiation detection at Pacific Northwest National Laboratory at the Hanford Site in Washington State. High Z, high resistivity, amorphous semiconductors are being designed for use as solid-state detectors at near ambient temperatures; principles of operation are analogous to single-crystal semiconducting detectors. Amorphous semiconductors have both advantages and disadvantages compared to single crystals, and this project is developing methods to mitigate technical problems and design optimized material for gamma detection. Several issues involved in the fabrication of amorphous semiconductors are described, including reaction thermodynamics and kinetics, the development of pyrolytic coating, and the synthesis of ingots. The characterization of amorphous semiconductors is described, including sectioning and polishing protocols, optical microscopy, X-ray diffraction, scanning electron microscopy, optical spectroscopy, particle-induced X-ram emission, Rutherford backscattering, and electrical testing. Then collaboration with the University of Illinois at Urbana-Champaign is discussed in the areas of Hall-effect measurements and current voltage data. Finally, we discuss the strategy for continuing the program.

  2. Apatite Formation from Amorphous Calcium Phosphate and Mixed Amorphous Calcium Phosphate/Amorphous Calcium Carbonate.

    PubMed

    Ibsen, Casper J S; Chernyshov, Dmitry; Birkedal, Henrik

    2016-08-22

    Crystallization from amorphous phases is an emerging pathway for making advanced materials. Biology has made use of amorphous precursor phases for eons and used them to produce structures with remarkable properties. Herein, we show how the design of the amorphous phase greatly influences the nanocrystals formed therefrom. We investigate the transformation of mixed amorphous calcium phosphate/amorphous calcium carbonate phases into bone-like nanocrystalline apatite using in situ synchrotron X-ray diffraction and IR spectroscopy. The speciation of phosphate was controlled by pH to favor HPO4 (2-) . In a carbonate free system, the reaction produces anisotropic apatite crystallites with large aspect ratios. The first formed crystallites are highly calcium deficient and hydrogen phosphate rich, consistent with thin octacalcium phosphate (OCP)-like needles. During growth, the crystallites become increasingly stoichiometric, which indicates that the crystallites grow through addition of near-stoichiometric apatite to the OCP-like initial crystals through a process that involves either crystallite fusion/aggregation or Ostwald ripening. The mixed amorphous phases were found to be more stable against phase transformations, hence, the crystallization was inhibited. The resulting crystallites were smaller and less anisotropic. This is rationalized by the idea that a local phosphate-depletion zone formed around the growing crystal until it was surrounded by amorphous calcium carbonate, which stopped the crystallization. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Structure and Properties of Amorphous Transparent Conducting Oxides

    NASA Astrophysics Data System (ADS)

    Medvedeva, Julia

    Driven by technological appeal, the research area of amorphous oxide semiconductors has grown tremendously since the first demonstration of the unique properties of amorphous indium oxide more than a decade ago. Today, amorphous oxides, such as a-ITO, a-IZO, a-IGZO, or a-ZITO, exhibit the optical, electrical, thermal, and mechanical properties that are comparable or even superior to those possessed by their crystalline counterparts, pushing the latter out of the market. Large-area uniformity, low-cost low-temperature deposition, high carrier mobility, optical transparency, and mechanical flexibility make these materials appealing for next-generation thin-film electronics. Yet, the structural variations associated with crystalline-to-amorphous transition as well as their role in carrier generation and transport properties of these oxides are far from being understood. Although amorphous oxides lack grain boundaries, factors like (i) size and distribution of nanocrystalline inclusions; (ii) spatial distribution and clustering of incorporated cations in multicomponent oxides; (iii) formation of trap defects; and (iv) piezoelectric effects associated with internal strains, will contribute to electron scattering. In this work, ab-initio molecular dynamics (MD) and accurate density-functional approaches are employed to understand how the properties of amorphous ternary and quaternary oxides depend on quench rates, cation compositions, and oxygen stoichiometries. The MD results, combined with thorough experimental characterization, reveal that interplay between the local and long-range structural preferences of the constituent oxides gives rise to a complex composition-dependent structural behavior in the amorphous oxides. The proposed network models of metal-oxygen polyhedra help explain the observed intriguing electrical and optical properties in In-based oxides and suggest ways to broaden the phase space of amorphous oxide semiconductors with tunable properties. The

  4. Fabrication of amorphous diamond films

    DOEpatents

    Falabella, S.

    1995-12-12

    Amorphous diamond films having a significant reduction in intrinsic stress are prepared by biasing a substrate to be coated and depositing carbon ions thereon under controlled temperature conditions. 1 fig.

  5. Amorphous and Ultradisperse Crystalline Materials,

    DTIC Science & Technology

    The book sums up experimental and theoretical findings on amorphous and ultradisperse crystalline materials , massive and film types. Present-day... crystalline materials of metallic systems are presented. Emphasis is placed on inorganic film materials.

  6. Characterization Techniques for Amorphous Alloys

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 2 http://dx.doi.org/10.1007/9getType="URL"/> 'Systems from B-Be-Fe to Co-W-Zr' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter '2 Characterization Techniques for Amorphous Alloys' with the content:

  7. Amorphous metal alloy and composite

    DOEpatents

    Wang, Rong; Merz, Martin D.

    1985-01-01

    Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

  8. Toll-like Receptors-2 and 4 are overexpressed in an experimental model of particle-induced osteolysis

    PubMed Central

    Valladares, Roberto D.; Nich, Christophe; Zwingenberger, Stefan; Li, Chenguang; Swank, Katherine R.; Gibon, Emmanuel; Rao, Allison J.; Yao, Zhenyu; Goodman, Stuart B.

    2014-01-01

    Aseptic loosening secondary to particle-associated periprosthetic osteolysis remains a major cause of failure of total joint replacements (TJR) in the mid- and long-term. As sentinels of the innate immune system, macrophages are central to the recognition and initiation of the inflammatory cascade which results in the activation of bone resorbing osteoclasts. Toll-like receptors (TLRs) are involved in the recognition of pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPS). Experimentally, polymethylmethacrylate (PMMA) and polyethylene (PE) particles have been shown to activate macrophages via the TLR pathway. The specific TLRs involved in PE particle-induced osteolysis remain largely unknown. We hypothesized that TLR-2, -4 and -9 mediated responses play a critical role in the development of PE wear particle-induced osteolysis in the murine calvarium model. To test this hypothesis, we first demonstrated that PE particles caused observable osteolysis, visible by microCT and bone histomorphometry when the particles were applied to the calvarium of C57BL/6 mice. The number of TRAP positive osteoclasts was significantly greater in the PE-treated group when compared to the control group without particles. Finally, using immunohistochemistry, TLR-2 and TLR-4 were highly expressed in PE particle-induced osteolytic lesions, whereas TLR-9 was downregulated. TLR-2 and -4 may represent novel therapeutic targets for prevention of wear particle-induced osteolysis and accompanying TJR failure. PMID:24115330

  9. ULTRAFINE CARBON PARTICLES INDUCE IL-8 EXPRESSION IN HUMAN AIRWAY EPITHELIAL CELLS THROUGH A POST-TRANSCRIPTIONAL MECHANISM

    EPA Science Inventory

    Ultrafine carbon particles induce IL-8 expression in human airway
    epithelial cells through a post-transcritpional mechanism
    Epidemiological studies suggest that ultrafine particles contribute to
    particulate matter (PM) - induced adverse health effects. IL-8 is an
    i...

  10. Recent advances in the characterization of amorphous pharmaceuticals by X-ray diffractometry.

    PubMed

    Thakral, Seema; Terban, Maxwell W; Thakral, Naveen K; Suryanarayanan, Raj

    2016-05-01

    For poorly water soluble drugs, the amorphous state provides an avenue to enhance oral bioavailability. The preparation method, in addition to sample history, can dictate the nature and the stability of the amorphous phase. Conventionally, X-ray powder diffractometry is of limited utility for characterization, but structural insights into amorphous and nanocrystalline materials have been enabled by coupling X-ray total scattering with the pair distribution function. This has shown great promise for fingerprinting, quantification, and even modeling of amorphous pharmaceutical systems. A consequence of the physical instability of amorphous phases is their crystallization propensity, and recent instrumental advances have substantially enhanced our ability to detect and quantify crystallization in a variety of complex matrices. The International Centre for Diffraction Data has a collection of the X-ray diffraction patterns of amorphous drugs and excipients and, based on the available supporting information, provides a quality mark of the data.

  11. Amorphous carbon for photovoltaics

    NASA Astrophysics Data System (ADS)

    Risplendi, Francesca; Grossman, Jeffrey C.

    2015-03-01

    All-carbon solar cells have attracted attention as candidates for innovative photovoltaic devices. Carbon-based materials such as graphene, carbon nanotubes (CNT) and amorphous carbon (aC) have the potential to present physical properties comparable to those of silicon-based materials with advantages such as low cost and higher thermal stability.In particular a-C structures are promising systems in which both sp2 and sp3 hybridization coordination are present in different proportions depending on the specific density, providing the possibility of tuning their optoelectronic properties and achieving comparable sunlight absorption to aSi. In this work we employ density functional theory to design suitable device architectures, such as bulk heterojunctions (BHJ) or pn junctions, consisting of a-C as the active layer material.Regarding BHJ, we study interfaces between aC and C nanostructures (such as CNT and fullerene) to relate their optoelectronic properties to the stoichiometry of aC. We demonstrate that the energy alignment between the a-C mobility edges and the occupied and unoccupied states of the CNT or C60 can be widely tuned by varying the aC density to obtain a type II interface.To employ aC in pn junctions we analyze the p- and n-type doping of a-C focusingon an evaluation of the Fermi level and work function dependence on doping.Our results highlight promising features of aC as the active layer material of thin-film solar cells.

  12. Particle induced X-ray emission-computed tomography analysis of an adsorbent for extraction chromatography

    NASA Astrophysics Data System (ADS)

    Satoh, Takahiro; Yokoyama, Akihito; Kitamura, Akane; Ohkubo, Takeru; Ishii, Yasuyuki; Takahatake, Yoko; Watanabe, Sou; Koma, Yoshikazu; Kada, Wataru

    2016-03-01

    Nd, which simulates minor actinides (MAs), was used for investigating residual minor actinides produced during the extraction chromatography separation of spent fuel from fast neutron reactors. A cross-sectional distribution of Nd in a minute globular adsorbent having diameter less than 50 μm was obtained using particle induced X-ray emission-computed tomography with a 3-MeV proton microbeam. The measurement area was 150 × 150 μm2 corresponding to 128 × 128 imaging pixels in projection images with 9° resolution, image reconstruction was carried out by a modified ML-EM (maximum likelihood expectation maximization) method. As a result, the cross-sectional distribution of Nd in the adsorbent was successfully obtained, and it was first revealed that Nd existed both in the central region and on the outer surface even after an elution. This implies that the internal structure of the adsorbent must be modified for improving of the recovery of MAs.

  13. Mechanisms of particle-induced pulmonary inflammation in a mouse model: exposure to wood dust.

    PubMed

    Määttä, Juha; Lehto, Maili; Leino, Marina; Tillander, Sari; Haapakoski, Rita; Majuri, Marja-Leena; Wolff, Henrik; Rautio, Sari; Welling, Irma; Husgafvel-Pursiainen, Kirsti; Savolainen, Kai; Alenius, Harri

    2006-09-01

    Repeated airway exposure to wood dust has long been known to cause adverse respiratory effects such as asthma and chronic bronchitis and impairment of lung function. However, the mechanisms underlying the inflammatory responses of the airways after wood dust exposure are poorly known. We used a mouse model to elucidate the mechanisms of particle-induced inflammatory responses to fine wood dust particles. BALB/c mice were exposed to intranasally administered fine (more than 99% of the particles had a particle size of < or = 5 microm, with virtually identical size distribution) birch or oak dusts twice a week for 3 weeks. PBS, LPS, and titanium dioxide were used as controls. Intranasal instillation of birch or oak dusts elicited influx of inflammatory cells to the lungs in mice. Enhancement of lymphocytes and neutrophils was seen after oak dust exposure, whereas eosinophil infiltration was higher after birch dust exposure. Infiltration of inflammatory cells was associated with an increase in the mRNA levels of several cytokines, chemokines, and chemokine receptors in lung tissue. Oak dust appeared to be a more potent inducer of these inflammatory mediators than birch dust. The results from our in vivo mouse model show that repeated airway exposure to wood dust can elicit lung inflammation, which is accompanied by induction of several proinflammatory cytokines and chemokines. Oak and birch dusts exhibited quantitative and qualitative differences in the elicitation of pulmonary inflammation, suggesting that the inflammatory responses induced by the wood species may rise via different cellular mechanisms.

  14. Modeling particle-induced electron emission in a simplified plasma Test Cell

    SciTech Connect

    Giuliano, Paul N.; Boyd, Iain D.

    2013-03-21

    Particle-induced electron emission (PIE) is modeled in a simplified, well-characterized plasma Test Cell operated at UCLA. In order for PIE to be a useful model in this environment, its governing equations are first reduced to lower-order models which can be implemented in a direct simulation Monte Carlo and Particle-in-Cell framework. These reduced-order models are described in full and presented as semi-empirical models. The models are implemented to analyze the interaction of low- and high-energy ({approx}1-2 keV) xenon ions and atoms with the stainless steel electrodes of the Test Cell in order to gain insight into the emission and transport of secondary electrons. Furthermore, there is a lack of data for xenon-stainless steel atom- and ion-surface interactions for similar environments. Using experimental data as a reference, both total yields and emitted electron energy distribution functions can be deduced by observing sensitivities of current collection results to these numerical models and their parameters.

  15. Composition of Renaissance paint layers: simultaneous particle induced X-ray emission and backscattering spectrometry.

    PubMed

    de Viguerie, L; Beck, L; Salomon, J; Pichon, L; Walter, Ph

    2009-10-01

    Particle induced X-ray emission spectroscopy (PIXE) is now routinely used in the field of cultural heritage. Various setups have been developed to investigate the elemental composition of wood/canvas paintings or of cross-section samples. However, it is not possible to obtain information concerning the quantity of organic binder. Backscattering spectrometry (BS) can be a useful complementary method to overcome this limitation. In the case of paint layers, PIXE brings the elemental composition (major elements to traces) and the BS spectrum can give access to the proportion of pigment and binder. With the use of 3 MeV protons for PIXE and BS simultaneously, it was possible to perform quantitative analysis including C and O for which the non-Rutherford cross sections are intense. Furthermore, with the use of the same conditions for PIXE and BS, the experiment time and the potential damage by the ion beam were reduced. The results obtained with the external beam of the Accélérateur Grand Louvre pour l'Analyse Elementaire (AGLAE) facility on various test painting samples and on cross sections from Italian Renaissance masterpieces are shown. Simultaneous combination of PIXE and BS leads to a complete characterization of the paint layers: elemental composition and proportion of the organic binder have been determined and thus provide useful information about ancient oil painting recipes.

  16. Particle-Induced X-Ray Emission (PIXE) Of Silicate Coatings On High Impact Resistance Polycarbonates

    NASA Astrophysics Data System (ADS)

    Xing, Qian; Hart, M. A.; Culbertson, R. J.; Bradley, J. D.; Herbots, N.; Wilkens, Barry J.; Sell, David A.; Watson, Clarizza Fiel

    2011-06-01

    Particle-Induced X-ray Emission (PIXE) analysis was employed to characterize hydroxypropyl methylcellulose (HPMC) C32H60O19 polymer film via areal density measurement on silicon-based substrates utilizing the differential PIXE concept, and compared with Rutherford backscattering spectrometry (RBS) results. It is demonstrated in this paper that PIXE and RBS measurements both yield comparable results for areal densities ranging from 1018 atom/cm2 to several 1019 atom/cm2. A collection of techniques including PIXE, RBS, tapping mode atomic force microscopy (TMAFM), and contact angle analysis were used to compute surface free energy, analyze surface topography and roughness parameters, determine surface composition and areal density, and to predict the water affinity and condensation behaviors of silicates and other compounds used for high impact resistance vision ware coatings. The visor surface under study is slightly hydrophilic, with root mean square of surface roughness on the order of one nm, and surface wavelength between 200 nm and 300 nm. Water condensation can be controlled on such surfaces via polymers adsorption. HPMC polymer areal density measurement supports the analysis of the surface water affinity and topography and the subsequent control of condensation behavior. HPMC film between 1018 atom/cm2 and 1019 atom/cm2 was found to effectively alter the water condensation pattern and prevents fogging by forming a wetting layer during condensation.

  17. Particle-induced indentation of the alveolar epithelium caused by surface tension forces

    PubMed Central

    Kojic, M.; Tsuda, A.

    2010-01-01

    Physical contact between an inhaled particle and alveolar epithelium at the moment of particle deposition must have substantial effects on subsequent cellular functions of neighboring cells, such as alveolar type-I, type-II pneumocytes, alveolar macrophage, as well as afferent sensory nerve cells, extending their dendrites toward the alveolar septal surface. The forces driving this physical insult are born at the surface of the alveolar air-liquid layer. The role of alveolar surfactant submerging a hydrophilic particle has been suggested by Gehr and Schürch's group (e.g., Respir Physiol 80: 17–32, 1990). In this paper, we extended their studies by developing a further comprehensive and mechanistic analysis. The analysis reveals that the mechanics operating in the particle-tissue interaction phenomena can be explained on the basis of a balance between surface tension force and tissue resistance force; the former tend to move a particle toward alveolar epithelial cell surface, the latter to resist the cell deformation. As a result, the submerged particle deforms the tissue and makes a noticeable indentation, which creates unphysiological stress and strain fields in tissue around the particle. This particle-induced microdeformation could likely trigger adverse mechanotransduction and mechanosensing pathways, as well as potentially enhancing particle uptake by the cells. PMID:20634359

  18. The effect of energetic particle induced geodesic acoustic modes on microturbulence

    NASA Astrophysics Data System (ADS)

    Schneller, Mirjam; Fu, Guoyong; Wang, Weixing; Chavdarovski, Ilija; Lauber, Philipp

    2016-10-01

    The control of turbulent transport reveals essential to achieve a successful fusion reactor. Together with turbulence, energetic particles are ubiquitous in present and future tokamaks due to heating systems and fusion reactions. Anisotropy in the distribution function of the energetic particle population is able to excite oscillations from the continuous spectrum of geodesic acoustic modes, which cannot be driven by plasma pressure gradients due to their toroidally and nearly poloidally symmetric structures. These oscillations are known as energetic particle-induced geodesic acoustic modes (EGAMs) [G.Y.Fu'08] and have been observed in recent experiments [R.Nazikian'08]. EGAMs are particularly attractive in the framework of turbulence regulation, since they lead to an oscillatory radial electric shear which can potentially saturate the turbulence. In recent years, numerical simulations have shown however, that turbulent transport could also be enhanced in the presence of EGAMs [D.Zarzoso'13]. For the presented work, the nonlinear gyrokinetic, electrostatic, particle-in-cell code GTS [W.X.Wang'06] has been extended to include an energetic particle population. With this new tool, the interaction of EGAMs with microturbulence is investigated in more detail. NERSC computing time is greatfully acknowledged.

  19. Recent advances in particle-induced X-ray emission analysis applied to biological samples

    NASA Astrophysics Data System (ADS)

    Mangelson, Nolan F.; Hill, Max W.

    1981-03-01

    Papers reporting the application of particle induced X-ray emission (PIXE) analysis to biological samples continue to appear regularly in the literature. The majority of these papers deal with blood, hair, and other common body organs while a few deal with biological samples from the environment. A variety of sample preparation methods have been demonstrated, a number of which are improvements, refinements and extensions of the thick- and thin-sample preparation methods reported in the early development of PIXE. While many papers describe the development of PIXE techniques some papers are now describing application of the methods to serious biological problems. The following two factors may help to stimulate more consistent use of the PIXE method. First, each PIXE facility should be organized to give rapid sample processing and should have available several sample preparation and handling methods. Second, those with the skill to use PIXE methods need to become closely associated with researchers knowledgeable in medical and biological sciences and they also need to become more involved in project planning and sample handling.

  20. Chitin particles induce size-dependent but carbohydrate-independent innate eosinophilia

    PubMed Central

    Kogiso, Mari; Nishiyama, Akihito; Shinohara, Tsutomu; Nakamura, Masataka; Mizoguchi, Emiko; Misawa, Yoshinori; Guinet, Elisabeth; Nouri-Shirazi, Mahyar; Dorey, C. Kathleen; Henriksen, Ruth Ann; Shibata, Yoshimi

    2011-01-01

    Murine Mφ that phagocytose CMP develop into M1; this response depends on the size and the chemical composition of the particles. In contrast, recent studies concluded that chitin particles induce M2 and eosinophil migration, promoting acquired Th2 immune responses against chitin-containing microbes or allergens. This study examined whether these apparently inconsistent responses to chitin could be induced by variation in the size and chemical composition of the chitin particles. We compared the responses of Mφ with CMP, LCB, and Sephadex G-100 beads (>40 μm). Beads were given i.p. to WT mice and to mice deficient in a CRTH2, a receptor for the eosinophil chemoattractant PGD2. In contrast to the M1 activation induced by CMP, i.p. administration of LCB or Sephadex beads induced within 24 h a CRTH2-dependent peritoneal eosinophilia, as well as CRTH2-independent activation of peritoneal Mφ that expressed Arg I, an M2 phenotype. LCB-induced Mφ exhibited elevated Arg I and a surface MR, reduced surface TLR2 levels, and no change in the levels of CHI3L1 or IL-10 production. Our results indicate that the effects of chitin in vivo are highly dependent on particle size and that large, nonphagocytosable beads, independent of their chemical composition, induce innate eosinophilia and activate Mφ expressing several M2, but not M1, phenotypes. PMID:21447645

  1. Allotropic composition of amorphous carbon

    SciTech Connect

    Yastrebov, S. G. Ivanov-Omskii, V. I.

    2007-08-15

    Using the concept of an inhomogeneous broadening of spectral lines of the basic oscillators responsible for forming the spectrum, the experimental dependences of the dispersion of the imaginary part of permittivity are analyzed for amorphous carbon. It turned out that four types of oscillators contribute to this dependence. The first three types represent the electron transitions from the energy-spectrum ground state for {pi} and {sigma} electrons of amorphous carbon to an excited state. The fourth type is related to the absorption of electromagnetic radiation by free charge carriers. The absolute values of squared plasma frequencies of oscillators are estimated, and, using them, the relative fraction of sp{sup 2}-bonded atoms forming the amorphous-carbon skeleton is calculated. This estimate agrees closely with the theoretical predictions for amorphous carbon of the same density as the material under study. The dependence of the relative fraction of sp{sup 2}-bonded atoms contained in amorphous hydrogenised carbon on annealing temperature is determined. The developed method is also applied to the analysis of the normalized curve for the light extinction in the interstellar medium. The contribution to the extinction of two varieties of interstellar matter is detected.

  2. Clathrate hydrate formation in amorphous cometary ice analogs in vacuo

    NASA Technical Reports Server (NTRS)

    Blake, David; Allamandola, Louis; Sandford, Scott; Hudgins, Doug; Freund, Friedemann

    1991-01-01

    Experiments conducted in clathrate hydrates with a modified electron microscope have demonstrated the possibility of such compounds' formation during the warming of vapor-deposited amorphous ices in vacuo, through rearrangements in the solid state. Subsolidus crystallization of compositionally complex amorphous ices may therefore be a general and ubiquitous process. Phase separations and microporous textures thus formed may be able to account for such anomalous cometary phenomena as the release of gas at large radial distances from the sun and the retention of volatiles to elevated temperatures.

  3. Clathrate hydrate formation in amorphous cometary ice analogs in vacuo

    NASA Technical Reports Server (NTRS)

    Blake, David; Allamandola, Louis; Sandford, Scott; Hudgins, Doug; Freund, Friedemann

    1991-01-01

    Experiments conducted in clathrate hydrates with a modified electron microscope have demonstrated the possibility of such compounds' formation during the warming of vapor-deposited amorphous ices in vacuo, through rearrangements in the solid state. Subsolidus crystallization of compositionally complex amorphous ices may therefore be a general and ubiquitous process. Phase separations and microporous textures thus formed may be able to account for such anomalous cometary phenomena as the release of gas at large radial distances from the sun and the retention of volatiles to elevated temperatures.

  4. Nanostructures having crystalline and amorphous phases

    DOEpatents

    Mao, Samuel S; Chen, Xiaobo

    2015-04-28

    The present invention includes a nanostructure, a method of making thereof, and a method of photocatalysis. In one embodiment, the nanostructure includes a crystalline phase and an amorphous phase in contact with the crystalline phase. Each of the crystalline and amorphous phases has at least one dimension on a nanometer scale. In another embodiment, the nanostructure includes a nanoparticle comprising a crystalline phase and an amorphous phase. The amorphous phase is in a selected amount. In another embodiment, the nanostructure includes crystalline titanium dioxide and amorphous titanium dioxide in contact with the crystalline titanium dioxide. Each of the crystalline and amorphous titanium dioxide has at least one dimension on a nanometer scale.

  5. Quantification of particle-induced inflammatory stress response: a novel approach for toxicity testing of earth materials.

    PubMed

    Harrington, Andrea D; Tsirka, Stella E; Schoonen, Martin Aa

    2012-04-18

    Reactive oxygen species (ROS) are vital regulators of many cellular functions in the body. The intracellular ROS concentration is highly regulated by a balance between pro-oxidants and anti-oxidants. A chronic excess of pro-oxidants leads to elevated ROS concentrations and inflammation, possibly initiating or enhancing disease onset. Mineral-induced generation of ROS, the role of minerals in upregulating cellular ROS, and their role in the development of several occupational diseases are now widely recognized. However, there is no standard protocol to determine changes in ROS production in cells after exposure to mineral dust or earth materials in general. In this study, a new method for determining the degree of cellular toxicity (i.e., cytotoxicity) of particles is described that will help bridge the gap in knowledge. By measuring the production of ROS and the viability of cells, an inflammatory stress response (ISR) indicator is defined. This approach normalizes the ROS upregulation with respect to the number of viable cells at the time of measurement. We conducted experiments on a series of minerals and soils that represent materials that are inert (i.e., glass beads, anatase, and a soil with low trace element content), moderately reactive (i.e., soil with high trace element content), and highly reactive (i.e., pyrite). Inert materials generated the lowest ISR, averaging 350% compared to the control. Acid washed pyrite produced the highest ISR (1,100 fold higher than the control). The measurements conducted as a function of time showed a complex response. Most materials showed an increase in ISR with particle loading. The amount of cellularly generated ROS and cell viability combined provide a better understanding of particle-induced oxidative stress. The results indicate that some earth materials may solicit an initial burst of ROS, followed by a second phase in which cell viability decreases and ROS production increases, leading to a high ISR value. Hence

  6. Amorphous-diamond electron emitter

    DOEpatents

    Falabella, Steven

    2001-01-01

    An electron emitter comprising a textured silicon wafer overcoated with a thin (200 .ANG.) layer of nitrogen-doped, amorphous-diamond (a:D-N), which lowers the field below 20 volts/micrometer have been demonstrated using this emitter compared to uncoated or diamond coated emitters wherein the emission is at fields of nearly 60 volts/micrometer. The silicon/nitrogen-doped, amorphous-diamond (Si/a:D-N) emitter may be produced by overcoating a textured silicon wafer with amorphous-diamond (a:D) in a nitrogen atmosphere using a filtered cathodic-arc system. The enhanced performance of the Si/a:D-N emitter lowers the voltages required to the point where field-emission displays are practical. Thus, this emitter can be used, for example, in flat-panel emission displays (FEDs), and cold-cathode vacuum electronics.

  7. Generalized melting criterion for amorphization

    SciTech Connect

    Devanathan, R. |; Lam, N.Q.; Okamoto, P.R.; Meshii, M.

    1992-12-01

    We present a thermodynamic model of solid-state amorphization based on a generalization of the well-known Lindemann criterion. The original Lindemann criterion proposes that melting occurs when the root-mean-square amplitude of thermal displacement exceeds a critical value. This criterion can be generalized to include solid-state amorphization by taking into account the static displacements. In an effort to verify the generalized melting criterion, we have performed molecular dynamics simulations of radiation-induced amorphization in NiZr, NiZr{sub 2}, NiTi and FeTi using embedded-atom potentials. The average shear elastic constant G was calculated as a function of the total mean-square atomic displacement following random atom-exchanges and introduction of Frenkel pairs. Results provide strong support for the generalized melting criterion.

  8. Energetic-particle-induced electromagnetic geodesic acoustic mode in tokamak plasmas

    SciTech Connect

    Wang, Lingfeng He, Zhixiong; He, Hongda; Shen, Y.; Dong, J. Q.

    2014-07-15

    Energetic-particle-induced kinetic electromagnetic geodesic acoustic modes (EKEGAMs) are numerically studied in low β (=plasma pressure/magnetic pressure) tokamak plasmas. The parallel component of the perturbed vector potential is considered along with the electrostatic potential perturbation. The effects of finite Larmor radius and finite orbit width of the bulk and energetic ions as well as electron parallel dynamics are all taken into account in the dispersion relation. Systematic harmonic and ordering analysis are performed for frequency and growth rate spectra of the EKEGAMs, assuming (kρ{sub i})∼q{sup −3}∼β≪1, where q, k, and ρ{sub i} are the safety factor, radial component of the EKEGAMs wave vector, and the Larmor radius of the ions, respectively. It is found that there exist critical β{sub h}/β{sub i} values, which depend, in particular, on pitch angle of energetic ions and safety factor, for the mode to be driven unstable. The EKEGAMs may also be unstable for pitch angle λ{sub 0}B<0.4 in certain parameter regions. Finite β effect of the bulk ions is shown to have damping effect on the EKEGAMs. Modes with higher radial wave vectors have higher growth rates. The damping from electron dynamics is found decreasing with decrease of the temperature ratio T{sub e}/T{sub i}. The modes are easily to be driven unstable in low safety factor q region and high temperature ratio T{sub h}/T{sub i} region. The harmonic features of the EKEGAMs are discussed as well.

  9. In situ pulmonary localization of air pollution particle-induced oxidative stress.

    PubMed

    Roberts, Elizabeth S; Malstrom, Scott E; Dreher, Kevin L

    2007-11-01

    Exposure to air particulate matter (PM) may be associated with increased morbidity and mortality. An improved understanding of the mechanism(s) by which PM induces adverse effects is needed. This preliminary study examined the ability to use unique bioluminescent technologies to identify acute localized areas of residual oil fly ash (ROFA)-induced, oxidative lung injury. Transgenic mice, in which luciferase (luc) expression was regulated by the heme oxygenase (HO)-1 promoter, were exposed by pharyngeal aspiration to either saline or 50 microg ROFA/mouse. HO-1-luc expression was determined at 2, 6, 12, and 24 h postexposure using luminescent quantification and Western blot analysis of lung protein extracts, as well as with a novel in situ pulmonary bioluminescence imaging approach. The different approaches for the detection of luciferase in lung protein extracts recovered from ROFA exposed HO-1-luc transgenic mice gave variable results. Pulmonary homogenate HO-1-luc levels were increased at 2 h and 24 h postexposure to ROFA when examined by chemilumescent and Western blot analyses, respectively. In situ bioluminescent imaging of pulmonary tissue sections detected ROFA-induced pulmonary luciferase expression by identifying highly localized increases in HO-1-luc expression at 12 h and 24 h postexposure. These results suggest that the variability observed in the methods of detection for luciferase may be due to a localization of cells expressing luciferase within tissue samples, demonstrating that the HO-1-luc transgenic mouse model is the preferred method to detect and pinpoint in vivo particle-induced, oxidative lung injury. The feasibility of using this in situ approach is a unique proof-of-concept application for the identification of localized sites of oxidative injury induced by environmental pollutants.

  10. Parametrized dielectric functions of amorphous GeSn alloys

    SciTech Connect

    D'Costa, Vijay Richard Wang, Wei; Yeo, Yee-Chia; Schmidt, Daniel

    2015-09-28

    We obtained the complex dielectric function of amorphous Ge{sub 1−x}Sn{sub x} (0 ≤ x ≤ 0.07) alloys using spectroscopic ellipsometry from 0.4 to 4.5 eV. Amorphous GeSn films were formed by room-temperature implantation of phosphorus into crystalline GeSn alloys grown by molecular beam epitaxy. The optical response of amorphous GeSn alloys is similar to amorphous Ge and can be parametrized using a Kramers-Kronig consistent Cody-Lorentz dispersion model. The parametric model was extended to account for the dielectric functions of amorphous Ge{sub 0.75}Sn{sub 0.25} and Ge{sub 0.50}Sn{sub 0.50} alloys from literature. The compositional dependence of band gap energy E{sub g} and parameters associated with the Lorentzian oscillator have been determined. The behavior of these parameters with varying x can be understood in terms of the alloying effect of Sn on Ge.

  11. Complexity.

    PubMed

    Gómez-Hernández, J Jaime

    2006-01-01

    It is difficult to define complexity in modeling. Complexity is often associated with uncertainty since modeling uncertainty is an intrinsically difficult task. However, modeling uncertainty does not require, necessarily, complex models, in the sense of a model requiring an unmanageable number of degrees of freedom to characterize the aquifer. The relationship between complexity, uncertainty, heterogeneity, and stochastic modeling is not simple. Aquifer models should be able to quantify the uncertainty of their predictions, which can be done using stochastic models that produce heterogeneous realizations of aquifer parameters. This is the type of complexity addressed in this article.

  12. Cocrystallization and amorphization induced by drug-excipient interaction improves the physical properties of acyclovir.

    PubMed

    Masuda, Takaaki; Yoshihashi, Yasuo; Yonemochi, Etsuo; Fujii, Kotaro; Uekusa, Hidehiro; Terada, Katsuhide

    2012-01-17

    Although acyclovir is one of the most important antiviral drugs used today, there are several problems with its physical properties. The aim of this study is to prepare cocrystals or amorphous complex of acyclovir using drug-excipient interactions to improve the physical properties of the drug, especially its dissolution rate and transdermal absorption. Screening for formation of cocrystals and the presence of amorphous acyclovir was conducted with various pharmaceutical excipinents, with the use of the solution-crystallization method and liquid-assisted cogrinding. The potential cocrystalline phase and the amorphized complex were characterized by PXRD, TG/DTA, IR, DSC and HPLC techniques. The screening indicated that acyclovir formed novel cocrystals with tartaric acid and was amorphized with citric acid. The acyclovir-tartaric acid cocrystal (ACV-TA cocrystal) structure was determined from synchrotron X-ray powder diffraction data. T(g) of the amorphous acyclovir-citric acid compound (ACV-CA amorphous) was determined by DSC. The initial dissolution rate of the ACV-TA cocrystals was considerably faster than that of anhydrous acyclovir. In vitro skin permeation of ACV-CA amorphous from polyethylene glycol (PEG) ointment was remarkably higher than that of the crystalline acyclovir. We successfully improved the physical properties of acyclovir by the cocrystallization and amorphization techniques, using pharmaceutical excipients.

  13. Autophagy mediated CoCrMo particle-induced peri-implant osteolysis by promoting osteoblast apoptosis

    PubMed Central

    Wang, Zhenheng; Liu, Naicheng; Liu, Kang; Zhou, Gang; Gan, Jingjing; Wang, Zhenzhen; Shi, Tongguo; He, Wei; Wang, Lintao; Guo, Ting; Bao, Nirong; Wang, Rui; Huang, Zhen; Chen, Jiangning; Dong, Lei; Zhao, Jianning; Zhang, Junfeng

    2015-01-01

    Wear particle-induced osteolysis is the leading cause of aseptic loosening, which is the most common reason for THA (total hip arthroplasty) failure and revision surgery. Although existing studies suggest that osteoblast apoptosis induced by wear debris is involved in aseptic loosening, the underlying mechanism linking wear particles to osteoblast apoptosis remains almost totally unknown. In the present study, we investigated the effect of autophagy on osteoblast apoptosis induced by CoCrMo metal particles (CoPs) in vitro and in a calvarial resorption animal model. Our study demonstrated that CoPs stimulated autophagy in osteoblasts and PIO (particle-induced osteolysis) animal models. Both autophagy inhibitor 3-MA (3-methyladenine) and siRNA of Atg5 could dramatically reduce CoPs-induced apoptosis in osteoblasts. Further, inhibition of autophagy with 3-MA ameliorated the severity of osteolysis in PIO animal models. Moreover, 3-MA also prevented osteoblast apoptosis in an antiautophagic way when tested in PIO model. Collectively, these results suggest that autophagy plays a key role in CoPs-induced osteolysis and that targeting autophagy-related pathways may represent a potential therapeutic approach for treating particle-induced peri-implant osteolysis. PMID:26566231

  14. Ultrastable Amorphous Sb2Se3 Film.

    PubMed

    Zhang, Kai; Li, Yang; Huang, Quan; Wang, Bihan; Zheng, Xuerong; Ren, Yang; Yang, Wenge

    2017-08-31

    Increasing the thermostability of amorphous materials has been a long journey to improve their properties. The metastable nature of chalcogenide glasses limits their practical applications as an amorphous semiconductor in photovoltaic performance. Here, we report the formation and physical properties of ultrastable amorphous Sb2Se3 with an enhanced thermal stability compared to ordinary amorphous Sb2Se3 (ΔTx= 17 K). By in situ high temperature-high energy synchrotron X-ray diffraction, the difference in structure relaxation between ordinary and ultrastable amorphous Sb2Se3 was manifested by local structure evolution. Ultrastable amorphous Sb2Se3 showed the smallest surface roughness and highest refractive index, the mechanism behind was further discussed in terms of fast molecular mobility and molecular orientation during vapor deposition. Formation of ultrastable amorphous Sb2Se3 demonstrated a promising avenue to obtain novel functional amorphous semiconductor with modulated structure and property.

  15. Imprinting bulk amorphous alloy at room temperature

    SciTech Connect

    Kim, Song-Yi; Park, Eun-Soo; Ott, Ryan T.; Lograsso, Thomas A.; Huh, Moo-Young; Kim, Do-Hyang; Eckert, Jürgen; Lee, Min-Ha

    2015-11-13

    We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the ability of amorphous alloys or metallic glasses to precisely replicate patterning features onto both conventional metals and the other amorphous alloys. In conclusion, our work presents an avenue for avoiding the embrittlement of amorphous alloys associated with thermoplastic forming and yields new insight the forming application of bulk amorphous alloys at room temperature without using heat treatment.

  16. Imprinting bulk amorphous alloy at room temperature

    PubMed Central

    Kim, Song-Yi; Park, Eun-Soo; Ott, Ryan T.; Lograsso, Thomas A.; Huh, Moo-Young; Kim, Do-Hyang; Eckert, Jürgen; Lee, Min-Ha

    2015-01-01

    We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the ability of amorphous alloys or metallic glasses to precisely replicate patterning features onto both conventional metals and the other amorphous alloys. Our work presents an avenue for avoiding the embrittlement of amorphous alloys associated with thermoplastic forming and yields new insight the forming application of bulk amorphous alloys at room temperature without using heat treatment. PMID:26563908

  17. Amorphous rare earth magnet powders

    SciTech Connect

    Sellers, C.H.; Branagan, D.J.; Hyde, T.A.; Lewis, L.H.; Panchanathan, V.

    1996-08-01

    Gas atomization (GA) processing does not generally have a high enough cooling rate to produce the initial amorphous microstructure needed to obtain optimal magnetic properties in RE{sub 2}Fe{sub 14}B alloys. Phase separation and an underquenched microstructure result from detrimental {alpha}-Fe precipitation, and the resulting magnetic domain structure is very coarse. Additionally, there is a dramatic dependence of the magnetic properties on the cooling rate (and therefore the particle size) and the powders can be sensitive to environmental degradation. Alloy compositions designed just for GA (as opposed to melt spinning) are necessary to produce an amorphous structure that can be crystallized to result in a fine structure with magnetic properties which are independent of particle size. The addition of titanium and carbon to the melt has been found to change the solidification process sufficiently to result in an ``overquenched`` state in which most of the powder size fractions have an amorphous component. Crystallization with a brief heat treatment produces a structure which has improved magnetic properties, in part due to the ability to use compositions with higher Fe contents without {alpha}-Fe precipitation. Results from magnetometry, magnetic force microscopy, and x-ray analyses will be used to contrast the microstructure, domain structure, and magnetic properties of this new generation of amorphous powders with their multiphase predecessors.

  18. Amorphous titanium-oxide supercapacitors

    NASA Astrophysics Data System (ADS)

    Fukuhara, Mikio; Kuroda, Tomoyuki; Hasegawa, Fumihiko

    2016-10-01

    The electric capacitance of an amorphous TiO2-x surface increases proportionally to the negative sixth power of the convex diameter d. This occurs because of the van der Waals attraction on the amorphous surface of up to 7 mF/cm2, accompanied by extreme enhanced electron trapping resulting from both the quantum-size effect and an offset effect from positive charges at oxygen-vacancy sites. Here we show that a supercapacitor, constructed with a distributed constant-equipment circuit of large resistance and small capacitance on the amorphous TiO2-x surface, illuminated a red LED for 37 ms after it was charged with 1 mA at 10 V. The fabricated device showed no dielectric breakdown up to 1,100 V. Based on this approach, further advances in the development of amorphous titanium-dioxide supercapacitors might be attained by integrating oxide ribbons with a micro-electro mechanical system.

  19. Model for amorphous aggregation processes

    NASA Astrophysics Data System (ADS)

    Stranks, Samuel D.; Ecroyd, Heath; van Sluyter, Steven; Waters, Elizabeth J.; Carver, John A.; von Smekal, Lorenz

    2009-11-01

    The amorphous aggregation of proteins is associated with many phenomena, ranging from the formation of protein wine haze to the development of cataract in the eye lens and the precipitation of recombinant proteins during their expression and purification. While much literature exists describing models for linear protein aggregation, such as amyloid fibril formation, there are few reports of models which address amorphous aggregation. Here, we propose a model to describe the amorphous aggregation of proteins which is also more widely applicable to other situations where a similar process occurs, such as in the formation of colloids and nanoclusters. As first applications of the model, we have tested it against experimental turbidimetry data of three proteins relevant to the wine industry and biochemistry, namely, thaumatin, a thaumatinlike protein, and α -lactalbumin. The model is very robust and describes amorphous experimental data to a high degree of accuracy. Details about the aggregation process, such as shape parameters of the aggregates and rate constants, can also be extracted.

  20. Optical absorption in amorphous silicon

    SciTech Connect

    O`Leary, S.K.; Zukotynski, S.; Perz, J.M.; Sidhu, L.S.

    1996-12-31

    The role that disorder plays in shaping the form of the optical absorption spectrum of hydrogenated amorphous silicon is investigated. Disorder leads to a redistribution of states, which both reduces the Tauc gap and broadens the absorption tail. The observed relationship between the Tauc gap and the breadth of the absorption tail is thus explained.

  1. Amorphous titanium-oxide supercapacitors

    PubMed Central

    Fukuhara, Mikio; Kuroda, Tomoyuki; Hasegawa, Fumihiko

    2016-01-01

    The electric capacitance of an amorphous TiO2-x surface increases proportionally to the negative sixth power of the convex diameter d. This occurs because of the van der Waals attraction on the amorphous surface of up to 7 mF/cm2, accompanied by extreme enhanced electron trapping resulting from both the quantum-size effect and an offset effect from positive charges at oxygen-vacancy sites. Here we show that a supercapacitor, constructed with a distributed constant-equipment circuit of large resistance and small capacitance on the amorphous TiO2-x surface, illuminated a red LED for 37 ms after it was charged with 1 mA at 10 V. The fabricated device showed no dielectric breakdown up to 1,100 V. Based on this approach, further advances in the development of amorphous titanium-dioxide supercapacitors might be attained by integrating oxide ribbons with a micro-electro mechanical system. PMID:27767103

  2. Photon hormesis deactivates alpha-particle induced bystander effects between zebrafish embryos

    NASA Astrophysics Data System (ADS)

    Ng, C. Y. P.; Cheng, S. H.; Yu, K. N.

    2017-04-01

    In the present work, we studied the effects of low-dose X-ray photons on the alpha-particle induced bystander effects between embryos of the zebrafish, Danio rerio. The effects on the naive whole embryos were studied through quantification of apoptotic signals (amounts of cells undergoing apoptosis) at 24 h post fertilization (hpf) using vital dye acridine orange staining, followed by counting the stained cells under a fluorescent microscope. We report data showing that embryos at 5 hpf subjected to a 4.4 mGy alpha-particle irradiation could release a stress signal into the medium, which could induce bystander effect in partnered naive embryos sharing the same medium. We also report that the bystander effect was deactivated when the irradiated embryos were subjected to a concomitant irradiation of 10 or 14 mGy of X-rays, but no such deactivation was achieved if the concomitant X-ray dose dropped to 2.5 or 5 mGy. In the present study, the significant drop in the amount of apoptotic signals on the embryos having received 4.4 mGy alpha particles together X-rays irradiation from 2.5 or 5 mGy to 10 or 14 mGy, together with the deactivation of RIBE with concomitant irradiation of 10 or 14 mGy of X-rays supported the participation of photon hormesis with an onset dose between 5 and 10 mGy, which might lead to removal of aberrant cells through early apoptosis or induction of high-fidelity DNA repair. As we found that photons and alpha particles could have opposite biological effects when these were simultaneously irradiated onto living organisms, these ionizing radiations could be viewed as two different environmental stressors, and the resultant effects could be regarded as multiple stressor effects. The present work presented the first study on a multiple stressor effect which occurred on bystander organisms. In other words, this was a non-targeted multiple stressor effect. The photon hormesis could also explain some failed attempts to observe neutron-induced bystander

  3. Therapeutic application of metallic nanoparticles combined with particle-induced x-ray emission effect

    NASA Astrophysics Data System (ADS)

    Kim, Jong-Ki; Seo, Seung-Jun; Kim, Ki-Hong; Kim, Tae-Jeong; Chung, Myung-Hwan; Kim, Kye-Ryung; Yang, Tae-Keun

    2010-10-01

    Metallic nanoparticles (MNP) are able to release localized x-rays when activated with a high energy proton beam by the particle-induced x-ray emission (PIXE) effect. The exploitation of this phenomenon in the therapeutic irradiation of tumors has been investigated. PIXE-based x-ray emission directed at CT26 tumor cells in vitro, when administered with either gold (average diameter 2 and 13 nm) or iron (average diameter 14 nm) nanoparticles (GNP or SNP), increased with MNP solution concentration over the range of 0.1-2 mg ml - 1. With irradiation by a 45 MeV proton therapy (PT) beam, higher concentrations had a decreased cell survival fraction. An in vivo study in CT26 mouse tumor models with tumor regression assay demonstrated significant tumor dose enhancement, thought to be a result of the PIXE effect when compared to conventional PT without MNP (radiation-only group) using a 45 MeV proton beam (p < 0.02). Those receiving GNP or SNP injection doses of 300 mg kg - 1 body weight before proton beam therapy demonstrated 90% or 75% tumor volume reduction (TVR) in 20 days post-PT while the radiation-only group showed only 18% TVR and re-growth of tumor volume after 20 days. Higher complete tumor regression (CTR) was observed in 14-24 days after a single treatment of PT with an average rate of 33-65% for those receiving MNP compared with 25% for the radiation-only group. A lower bound of therapeutic effective MNP concentration range, in vivo, was estimated as 30-79 µg g - 1 tissue for both gold and iron nanoparticles. The tumor dose enhancement may compensate for an increase in entrance dose associated with conventional PT when treating large, solid tumors with a spread-out Bragg peak (SOBP) technique. The use of a combined high energy Bragg peak PT with PIXE generated by MNP, or PIXE alone, may result in new treatment options for infiltrative metastatic tumors and other diffuse inflammatory diseases.

  4. Crystalline Polymorphism Emerging From a Milling-Induced Amorphous Form: The Case of Chlorhexidine Dihydrochloride.

    PubMed

    Elisei, Elena; Willart, Jean-François; Danède, Florence; Siepmann, Jürgen; Siepmann, Florence; Descamps, Marc

    2017-07-14

    In this paper, solid-state amorphization induced by mechanical milling is shown to be a useful tool to explore the polymorphism of drugs and their mechanism of devitrification. We show in particular how the recrystallization of amorphous chlorhexidine dihydrochloride obtained by milling reveals a complex polymorphism that involves several polymorphic forms. Two new crystalline forms are identified, one of them appearing as a highly disordered precursor state which however clearly differs from the amorphous one. Several interpretations are here proposed to describe the puzzling nature of this phase. In addition, the possibility to amorphize chlorhexidine dihydrochloride by milling allowed to determine the main physical characters of the amorphous state which cannot be obtained through the usual thermal quench of the liquid because of a strong chemical degradation occurring on melting. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  5. Flexible amorphous metal films with high stability

    NASA Astrophysics Data System (ADS)

    Liu, M.; Cao, C. R.; Lu, Y. M.; Wang, W. H.; Bai, H. Y.

    2017-01-01

    We report the formation of amorphous Cu50Zr50 films with a large-area of more than 100 cm2. The films were fabricated by ion beam assisted deposition with a slow deposition rate at moderate temperature. The amorphous films have markedly enhanced thermal stability, excellent flexibility, and high reflectivity with atomic level smoothness. The multifunctional properties of the amorphous films are favorites in the promising applications of smart skin or wearable devices. The method of preparing highly stable amorphous metal films by tuning the deposition rate instead of deposition temperature could pave a way for exploring amorphous metal films with unique properties.

  6. Pressure-induced silica quartz amorphization studied by iterative stochastic surface walking reaction sampling.

    PubMed

    Zhang, Xiao-Jie; Shang, Cheng; Liu, Zhi-Pan

    2017-02-08

    The crystal to amorphous transformation is a common phenomenon in Nature and has important impacts on material properties. Our current knowledge on such complex solid transformation processes is, however, limited because of their slow kinetics and the lack of long-range ordering in amorphous structures. To reveal the kinetics in the amorphization of solids, this work, by developing iterative reaction sampling based on the stochastic surface walking global optimization method, investigates the well-known crystal to amorphous transformation of silica (SiO2) under external pressures, the mechanism of which has long been debated for its non-equilibrium, pressure-sensitive kinetics and complex product components. Here we report for the first time the global potential energy surface (PES) and the lowest energy pathways for α-quartz amorphization from first principles. We show that the pressurization at 15 GPa, the reaction condition, can lift the quartz phase energetically close to the amorphous zone, which thermodynamically initializes the amorphization. More importantly, the large flexibility of Si cation coordination (including four, five and six coordination) results in many kinetically competing routes to more stable dense forms, including the known MI, stishovite, newly-identified MII and TI phases. All these pathways have high barriers due to the local Si-O bond breaking and are mediated by amorphous structures with five-fold Si. This causes simultaneous crystal-to-crystal and crystal-to-amorphous transitions. The high barrier and the reconstructive nature of the phase transition are the key kinetics origin for silica amorphization under pressures.

  7. Energy landscape of relaxed amorphous silicon

    NASA Astrophysics Data System (ADS)

    Valiquette, Francis; Mousseau, Normand

    2003-09-01

    We analyze the structure of the energy landscape of a well-relaxed 1000-atom model of amorphous silicon using the activation-relaxation technique (ART nouveau). Generating more than 40 000 events starting from a single minimum, we find that activated mechanisms are local in nature, that they are distributed uniformly throughout the model, and that the activation energy is limited by the cost of breaking one bond, independently of the complexity of the mechanism. The overall shape of the activation-energy-barrier distribution is also insensitive to the exact details of the configuration, indicating that well-relaxed configurations see essentially the same environment. These results underscore the localized nature of relaxation in this material.

  8. Spray drying formulation of amorphous solid dispersions.

    PubMed

    Singh, Abhishek; Van den Mooter, Guy

    2016-05-01

    Spray drying is a well-established manufacturing technique which can be used to formulate amorphous solid dispersions (ASDs) which is an effective strategy to deliver poorly water soluble drugs (PWSDs). However, the inherently complex nature of the spray drying process coupled with specific characteristics of ASDs makes it an interesting area to explore. Numerous diverse factors interact in an inter-dependent manner to determine the final product properties. This review discusses the basic background of ASDs, various formulation and process variables influencing the critical quality attributes (CQAs) of the ASDs and aspects of downstream processing. Also various aspects of spray drying such as instrumentation, thermodynamics, drying kinetics, particle formation process and scale-up challenges are included. Recent advances in the spray-based drying techniques are mentioned along with some future avenues where major research thrust is needed.

  9. Topological Insulators in Amorphous Systems

    NASA Astrophysics Data System (ADS)

    Agarwala, Adhip; Shenoy, Vijay B.

    2017-06-01

    Much of the current understanding of topological insulators, which informs the experimental search for topological materials and systems, is based on crystalline band theory, where local electronic degrees of freedom at different crystal sites hybridize with each other in ways that produce nontrivial topology. Here we provide a novel theoretical demonstration of realizing topological phases in amorphous systems, as exemplified by a set of sites randomly located in space. We show this by constructing hopping models on such random lattices whose gapped ground states are shown to possess nontrivial topological nature (characterized by Bott indices) that manifests as quantized conductances in systems with a boundary. Our study adds a new dimension, beyond crystalline solids, to the search for topological systems by pointing to the promising possibilities in amorphous solids and other engineered random systems.

  10. Topological Insulators in Amorphous Systems.

    PubMed

    Agarwala, Adhip; Shenoy, Vijay B

    2017-06-09

    Much of the current understanding of topological insulators, which informs the experimental search for topological materials and systems, is based on crystalline band theory, where local electronic degrees of freedom at different crystal sites hybridize with each other in ways that produce nontrivial topology. Here we provide a novel theoretical demonstration of realizing topological phases in amorphous systems, as exemplified by a set of sites randomly located in space. We show this by constructing hopping models on such random lattices whose gapped ground states are shown to possess nontrivial topological nature (characterized by Bott indices) that manifests as quantized conductances in systems with a boundary. Our study adds a new dimension, beyond crystalline solids, to the search for topological systems by pointing to the promising possibilities in amorphous solids and other engineered random systems.

  11. Proton microprobe and particle induced X-ray emission (PIXE) analysis for studies of pathological brain tissue

    SciTech Connect

    Malmqvist, K.G.; Brun, A.; Inamura, K.; Martins, E.; Salford, L.G.; Siesjoe, B.K.T.; Tapper, U.A.; Themner, K.

    1988-09-01

    Particle Induced X-ray Emission and proton microprobe analyses have been applied for the investigation of regional elemental distributions in connection with various pathological states in the brain. Malignant brain tumors and adjacent histologically intact tissue removed during surgery were analysed with PIXE. Systematic elemental variations, e.g., for calcium and selenium, were observed in the tumor front. The proton microprobe was applied to study the Ca and K concentrations in various cell strata in hippocampus following transient ischaemia in rat brain. Significant increases in the Ca level occurred in selectively vulnerable cells within 48 h after the ischaemia.

  12. Recrystallization of atomically balanced amorphous pockets in Si: A source of point defects

    SciTech Connect

    Marques, Luis A.; Pelaz, Lourdes; Lopez, Pedro; Santos, Ivan; Aboy, Maria

    2007-10-15

    We use classical molecular dynamics simulation techniques to study the regrowth behavior of amorphous pockets in Si. We demonstrate that crystallization depends on the morphology of the pocket-crystal interface. Although our simulated amorphous pockets had not any excess nor deficit of atoms with respect to perfect crystal, after regrowth we found residual defects. Most of them are single Si interstitials and vacancies, but also larger defects have been encountered. We have determined their atomic structures and calculated their formation energies. These complexes are more stable than amorphous pockets, and may trigger the formation of extended defects or favor damage accumulation.

  13. Electrodeposition of amorphous ternary nickel-chromium-phosphorus alloy

    DOEpatents

    Guilinger, Terry R.

    1990-01-01

    Amorphous ternary nickel-chromium-phosphorus alloys are electrodeposited from a bath comprising a nickel salt, a chromium salt, a phosphorus source such as sodium hypophosphite, a complexing agent for the nickel ions, supporting salts to increase conductivity, and a buffering agent. The process is carried out at about room temperature and requires a current density between about 20 to 40 A/dm.sup.2.

  14. On Structure and Properties of Amorphous Materials

    PubMed Central

    Stachurski, Zbigniew H.

    2011-01-01

    Mechanical, optical, magnetic and electronic properties of amorphous materials hold great promise towards current and emergent technologies. We distinguish at least four categories of amorphous (glassy) materials: (i) metallic; (ii) thin films; (iii) organic and inorganic thermoplastics; and (iv) amorphous permanent networks. Some fundamental questions about the atomic arrangements remain unresolved. This paper focuses on the models of atomic arrangements in amorphous materials. The earliest ideas of Bernal on the structure of liquids were followed by experiments and computer models for the packing of spheres. Modern approach is to carry out computer simulations with prediction that can be tested by experiments. A geometrical concept of an ideal amorphous solid is presented as a novel contribution to the understanding of atomic arrangements in amorphous solids. PMID:28824158

  15. Narrow band gap amorphous silicon semiconductors

    DOEpatents

    Madan, A.; Mahan, A.H.

    1985-01-10

    Disclosed is a narrow band gap amorphous silicon semiconductor comprising an alloy of amorphous silicon and a band gap narrowing element selected from the group consisting of Sn, Ge, and Pb, with an electron donor dopant selected from the group consisting of P, As, Sb, Bi and N. The process for producing the narrow band gap amorphous silicon semiconductor comprises the steps of forming an alloy comprising amorphous silicon and at least one of the aforesaid band gap narrowing elements in amount sufficient to narrow the band gap of the silicon semiconductor alloy below that of amorphous silicon, and also utilizing sufficient amounts of the aforesaid electron donor dopant to maintain the amorphous silicon alloy as an n-type semiconductor.

  16. Promotion of bone formation by naringin in a titanium particle-induced diabetic murine calvarial osteolysis model.

    PubMed

    Zhou, Xiaoxiao; Zhang, Peng; Zhang, Chao; Zhu, Zhen'an

    2010-04-01

    Diabetic patients have an increased risk of prosthesis failure requiring revision surgery. Furthermore, skeletal defects are observed in conjunction with type 1 diabetes. Using a titanium particle-induced calvarial osteolysis model in diabetic mice, we investigated the effect of diabetes on the osteolytic process and the role of naringin in its prevention. Three groups each of nondiabetic or diabetic mice were treated with vehicle only, with particles only, or with particles then naringin for 10 days. Alteration of bone indices near the midline suture were then analyzed by microcomputed tomography scanning and histology. Serum levels of osteocalcin (OCN) and cross-linked N-telopeptide of type I collagen (NTx) were measured by enzyme-linked immunosorbent assay. The decreases in new bone formation (p < 0.05), calvaria thickness (p < 0.05), bone volume (p < 0.05), midline suture area (p < 0.05), and OCN concentration (p < 0.05) found in diabetic mice were normalized with naringin treatment. Diabetic state promoted particle-induced osteolysis. Naringin, an osteoanabolic agent, improved bone indices apparently by stimulating bone formation. Therefore, naringin may be beneficial in preventing and treating debris-mediated periprosthetic osteolysis after total joint replacement, especially in diabetics.

  17. Therapeutic potential of the proteasome inhibitor Bortezomib on titanium particle-induced inflammation in a murine model.

    PubMed

    Mao, Xin; Pan, Xiaoyun; Cheng, Tao; Zhang, Xianlong

    2012-06-01

    Wear particle-induced aseptic loosening has been recognized as a harmful inflammatory process that jeopardizes the longevity of total joint replacement. The proteasome controls the activation of NF-κB and subsequent inflammatory mediators, such as TNF-α and IL-1β; thus, we investigated whether proteasome inhibition can ameliorate wear particle-induced inflammation in a murine model. A total of 48 BALB/C mice were divided into four groups. Titanium (Ti) particles were injected into the established air pouches of all mice (except negative controls) to provoke inflammation, and then 0.1 or 0.5 mg/kg of Bortezomib (Bzb, a proteasome inhibitor) was administered to ameliorate the inflammation response, while air pouches without Bzb administration were used as loading controls. The air pouches were harvested 2 or 7 days after Bzb injection for molecular and histological analyses. Inflammation responses in the air pouch tissues of Bzb treatment groups are lower than those in the Ti-stimulated group, and this occurs in a dose-dependent manner. Bzb can significantly attenuate the severity of Ti-induced inflammation in air pouches.

  18. Macrophage integrins modulate response to ultra-high molecular weight polyethylene particles and direct particle-induced osteolysis.

    PubMed

    Zaveri, Toral D; Dolgova, Natalia V; Lewis, Jamal S; Hamaker, Kiri; Clare-Salzler, Michael J; Keselowsky, Benjamin G

    2017-01-01

    Aseptic loosening due to peri-prosthetic osteolysis is one of the primary causes for failure of artificial joint replacements. Implant-derived wear particles, often ultra-high molecular weight polyethylene (UHMWPE) microparticles, initiate an inflammatory cascade upon phagocytosis by macrophages, which leads to osteoclast recruitment and activation, ultimately resulting in osteolysis. Investigation into integrin receptors, involved in cellular interactions with biomaterial-adsorbed adhesive proteins, is of interest to understand and modulate inflammatory processes. In this work, we investigate the role of macrophage integrins Mac-1 and RGD-binding integrins in response to UHMWPE wear particles. Using integrin knockout mice as well as integrin blocking techniques, reduction in macrophage phagocytosis and inflammatory cytokine secretion is demonstrated when these receptors are either absent or blocked. Along this line, various opsonizing proteins are shown to differentially modulate microparticle uptake and macrophage secretion of inflammatory cytokines. Furthermore, using a calvarial osteolysis model it is demonstrated that both Mac-1 integrin and RGD-binding integrins modulate the particle induced osteolysis response to UHMWPE microparticles, with a 40% decrease in the area of osteolysis by the absence or blocking of these integrins, in vivo. Altogether, these findings indicate Mac-1 and RGD-binding integrins are involved in macrophage-directed inflammatory responses to UHMWPE and may serve as therapeutic targets to mitigate wear particle induced peri-prosthetic osteolysis for improved performance of implanted joints.

  19. Particle-induced osteolysis is not accompanied by systemic remodeling but is reflected by systemic bone biomarkers.

    PubMed

    Ross, R D; Virdi, A S; Liu, S; Sena, K; Sumner, D R

    2014-07-01

    Particle-induced osteolysis is caused by an imbalance in bone resorption and formation, often leading to loss of implant fixation. Bone remodeling biomarkers may be useful for identification of osteolysis and studying pathogenesis, but interpretation of biomarker data could be confounded if local osteolysis engenders systemic bone remodeling. Our goal was to determine if remote bone remodeling contributes to biomarker levels. Serum concentrations of eight biomarkers and bone remodeling rates at local (femur), contiguous (tibia), and remote (humerus and lumbar vertebra) sites were evaluated in a rat model of particle-induced osteolysis. Serum CTX-1, cathepsin K, PINP, and OPG were elevated and osteocalcin was suppressed in the osteolytic group, but RANKL, TRAP 5b, and sclerostin were not affected at the termination of the study at 12 weeks. The one marker tested longitudinally (CTX-1) was elevated by 3 weeks. We found increased bone resorption and decreased bone formation locally, subtle differences in contiguous sites, but no differences remotely at 12 weeks. Thus, the skeletal response to local particle challenge was not systemic, implying that the observed differences in serum biomarker levels reflect differences in local remodeling. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

  20. NF-κB decoy oligodeoxynucleotide inhibits wear particle-induced inflammation in a murine calvarial model.

    PubMed

    Sato, Taishi; Pajarinen, Jukka; Lin, Tzu-hua; Tamaki, Yasunobu; Loi, Florence; Egashira, Kensuke; Yao, Zhenyu; Goodman, Stuart B

    2015-12-01

    Wear particles induce periprosthetic inflammation and osteolysis through activation of nuclear factor kappa B (NF-κB), which up-regulates the downstream target gene expression for proinflammatory cytokines in macrophages. It was hypothesized that direct suppression of NF-κB activity in the early phases of this disorder could be a therapeutic strategy for preventing the inflammatory response to wear particles, potentially mitigating osteolysis. NF-κB activity can be suppressed via competitive binding with double stranded NF-κB decoy oligodeoxynucleotides (ODNs) that blocks this transcription factor from binding to the promoter regions of targeted genes. In this murine calvarial study, clinically relevant polyethylene particles (PEs) with/without ODN were subcutaneously injected over the calvarial bone. In the presence of PE particles, macrophages migrated to the inflammatory site and induced tumor necrosis factor alpha (TNF-α) and receptor activator of nuclear factor kappa B ligand (RANKL) expression, resulting in an increase in the number of osteoclasts. Local injections of ODN mitigated the expression of TNF-α, RANKL, and induced the expression of two anti-inflammatory, antiresorptive cytokines: interleukin-1 receptor antagonist and osteoprotegerin. Local intervention with NF-κB decoy ODN in early cases of particle-induced inflammation in which the prosthesis is still salvageable may potentially preserve periprosthetic bone stock.

  1. Amorphous silicon solar cell allowing infrared transmission

    DOEpatents

    Carlson, David E.

    1979-01-01

    An amorphous silicon solar cell with a layer of high index of refraction material or a series of layers having high and low indices of refraction material deposited upon a transparent substrate to reflect light of energies greater than the bandgap energy of the amorphous silicon back into the solar cell and transmit solar radiation having an energy less than the bandgap energy of the amorphous silicon.

  2. Amorphous-Amorphous Phase Separation in API/Polymer Formulations.

    PubMed

    Luebbert, Christian; Huxoll, Fabian; Sadowski, Gabriele

    2017-02-15

    The long-term stability of pharmaceutical formulations of poorly-soluble drugs in polymers determines their bioavailability and therapeutic applicability. However, these formulations do not only often tend to crystallize during storage, but also tend to undergo unwanted amorphous-amorphous phase separations (APS). Whereas the crystallization behavior of APIs in polymers has been measured and modeled during the last years, the APS phenomenon is still poorly understood. In this study, the crystallization behavior, APS, and glass-transition temperatures formulations of ibuprofen and felodipine in polymeric PLGA excipients exhibiting different ratios of lactic acid and glycolic acid monomers in the PLGA chain were investigated by means of hot-stage microscopy and DSC. APS and recrystallization was observed in ibuprofen/PLGA formulations, while only recrystallization occurred in felodipine/PLGA formulations. Based on a successful modeling of the crystallization behavior using the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT), the occurrence of APS was predicted in agreement with experimental findings.

  3. The physics and applications of amorphous semiconductors

    SciTech Connect

    Madan, A.; Shaw, M.P.

    1988-01-01

    This is a treatise on the physics and applications of the new emerging technology of amorphous semiconductors. The authors focus upon research problems such as the optimization of device performance while also presenting the general physics of amorphous semiconductors. The first part of the book covers hydrogenated amorphous silicon type alloys, whose applications include inexpensive solar cells, thin film transistors, image scanners, electrophotography, optical recording, and gas sensors. The second part of the book discusses amorphous chalcogenides, whose applications include electrophotography, switching, and memory elements.

  4. Amorphous silicon based radiation detectors

    SciTech Connect

    Perez-Mendez, V.; Cho, G.; Drewery, J.; Jing, T.; Kaplan, S.N.; Qureshi, S.; Wildermuth, D. ); Fujieda, I.; Street, R.A. )

    1991-07-01

    We describe the characteristics of thin(1 {mu}m) and thick (>30{mu}m) hydrogenated amorphous silicon p-i-n diodes which are optimized for detecting and recording the spatial distribution of charged particles, x-rays and {gamma} rays. For x-ray, {gamma} ray, and charged particle detection we can use thin p-i-n photosensitive diode arrays coupled to evaporated layers of suitable scintillators. For direct detection of charged particles with high resistance to radiation damage, we use the thick p-i-n diode arrays. 13 refs., 7 figs.

  5. Preparation of amorphous sulfide sieves

    DOEpatents

    Siadati, Mohammad H.; Alonso, Gabriel; Chianelli, Russell R.

    2006-11-07

    The present invention involves methods and compositions for synthesizing catalysts/porous materials. In some embodiments, the resulting materials are amorphous sulfide sieves that can be mass-produced for a variety of uses. In some embodiments, methods of the invention concern any suitable precursor (such as thiomolybdate salt) that is exposed to a high pressure pre-compaction, if need be. For instance, in some cases the final bulk shape (but highly porous) may be same as the original bulk shape. The compacted/uncompacted precursor is then subjected to an open-flow hot isostatic pressing, which causes the precursor to decompose and convert to a highly porous material/catalyst.

  6. Structural study of amorphous polyaniline

    NASA Astrophysics Data System (ADS)

    Laridjani, M.; Pouget, J. P.; MacDiarmid, A. G.; Epstein, A. J.

    1992-06-01

    Many materials, especially polymers, have a substantial volume fraction with no long range crystalline order. Through these regions are often termed amorphous, they frequently have a specific local order. We describe and use here a method, base on a non-energy dispersive X-ray diffraction technique, to obtain good quality interference functions and, by Fourier transform, radial distribution functions of the amorphous structure of polymers. We apply this approach to members of a family of electronic polymers of current interest : polyaniline emeraldine bases. We show that the local order exhibits significant differences in type I and type II materials, precipitated as salt and base respectively. These studies demonstrate the importance of sample preparation in evaluating the physical properties of polyaniline, and provide a structural origin for memory effects observed in the doping-dedoping processes. Beaucoup de matériaux, spécialement les polymères, ont une importante fraction de leur volume sans ordre cristallin à longue portée. Bien que ces régions soient souvent appelées amorphes, elles présentent fréquemment un ordre local caractéristique. Nous décrivons et utilisons dans ce papier une méthode, basée sur une technique de diffraction de rayons X non dispersive en énergie, pour obtenir des fonctions d'interférence de bonne qualité et, par transformée de Fourier, la fonction de distribution radiale des polymères amorphes. Nous appliquons cette technique à plusieurs éléments d'une même famille de polymères électroniques d'intérêt actuel : les polyanilines éméraldine bases. Nous montrons que l'ordre local présente d'appréciables différences dans les matériaux de type I et II, préparés respectivement sous forme de sel et de base. Cette étude démontre l'importance des conditions de préparation sur les propriétés physiques du polyaniline et donne une base structurale aux effets observés dans les processus de dopage-dédopage de

  7. Comparative surface dynamics of amorphous and semicrystalline polymer films

    PubMed Central

    Becker, James S.; Brown, Ryan D.; Killelea, Daniel R.; Yuan, Hanqiu; Sibener, S. J.

    2011-01-01

    The surface dynamics of amorphous and semicrystalline polymer films have been measured using helium atom scattering. Time-of-flight data were collected to resolve the elastic and inelastic scattering components in the diffuse scattering of neutral helium atoms from the surface of a thin poly(ethylene terephthalate) film. Debye–Waller attenuation was observed for both the amorphous and semicrystalline phases of the polymer by recording the decay of elastically scattered helium atoms with increasing surface temperature. Thermal attenuation measurements in the specular scattering geometry yielded perpendicular mean-square displacements of 2.7•10-4 Å2 K-1 and 3.1•10-4 Å2 K-1 for the amorphous and semicrystalline surfaces, respectively. The semicrystalline surface was consistently ∼15% softer than the amorphous across a variety of perpendicular momentum transfers. The Debye–Waller factors were also measured at off-specular angles to characterize the parallel mean-square displacements, which were found to increase by an order of magnitude over the perpendicular mean-square displacements for both surfaces. In contrast to the perpendicular motion, the semicrystalline state was ∼25% stiffer than the amorphous phase in the surface plane. These results were uniquely accessed through low-energy neutral helium atom scattering due to the highly surface-sensitive and nonperturbative nature of these interactions. The goal of tailoring the chemical and physical properties of complex advanced materials requires an improved understanding of interfacial dynamics, information that is obtainable through atomic beam scattering methods. PMID:20713734

  8. Using machine learning to identify factors that govern amorphization of irradiated pyrochlores

    DOE PAGES

    Pilania, Ghanshyam; Whittle, Karl R.; Jiang, Chao; ...

    2017-02-10

    Structure–property relationships are a key materials science concept that enables the design of new materials. In the case of materials for application in radiation environments, correlating radiation tolerance with fundamental structural features of a material enables materials discovery. Here, we use a machine learning model to examine the factors that govern amorphization resistance in the complex oxide pyrochlore (A2B2O7) in a regime in which amorphization occurs as a consequence of defect accumulation. We examine the fidelity of predictions based on cation radii and electronegativities, the oxygen positional parameter, and the energetics of disordering and amorphizing the material. No one factormore » alone adequately predicts amorphization resistance. We find that when multiple families of pyrochlores (with different B cations) are considered, radii and electronegativities provide the best prediction, but when the machine learning model is restricted to only the B = Ti pyrochlores, the energetics of disordering and amorphization are critical factors. We discuss how these static quantities provide insight into an inherently kinetic property such as amorphization resistance at finite temperature. Lastly, this work provides new insight into the factors that govern the amorphization susceptibility and highlights the ability of machine learning approaches to generate that insight.« less

  9. Is Mg-stabilized amorphous calcium carbonate a homogeneous mixture of amorphous magnesium carbonate and amorphous calcium carbonate?

    PubMed

    Yang, Sheng-Yu; Chang, Hsun-Hui; Lin, Cang-Jie; Huang, Shing-Jong; Chan, Jerry C C

    2016-10-04

    We find two types of carbonate ions in Mg stabilized amorphous calcium carbonate (Mg-ACC), whose short-range orders are identical to those of ACC and amorphous magnesium carbonate (AMC). Mg-ACC comprises a homogeneous mixture of the nano-clusters of ACC and AMC. Their relative amount varies systematically at different pH.

  10. Laser surface treatment of amorphous metals

    NASA Astrophysics Data System (ADS)

    Katakam, Shravana K.

    Amorphous materials are used as soft magnetic materials and also as surface coatings to improve the surface properties. Furthermore, the nanocrystalline materials derived from their amorphous precursors show superior soft magnetic properties than amorphous counter parts for transformer core applications. In the present work, laser based processing of amorphous materials will be presented. Conventionally, the nanocrystalline materials are synthesized by furnace heat treatment of amorphous precursors. Fe-based amorphous/nanocrystalline materials due to their low cost and superior magnetic properties are the most widely used soft magnetic materials. However, achieving nanocrystalline microstructure in Fe-Si-B ternary system becomes very difficult owing its rapid growth rate at higher temperatures and sluggish diffusion at low temperature annealing. Hence, nanocrystallization in this system is achieved by using alloying additions (Cu and Nb) in the ternary Fe-Si-B system. Thus, increasing the cost and also resulting in reduction of saturation magnetization. laser processing technique is used to achieve extremely fine nanocrystalline microstructure in Fe-Si-B amorphous precursor. Microstructure-magnetic Property-laser processing co-relationship has been established for Fe-Si-B ternary system using analytical techniques. Laser processing improved the magnetic properties with significant increase in saturation magnetization and near zero coercivity values. Amorphous materials exhibit excellent corrosion resistance by virtue of their atomic structure. Fe-based amorphous materials are economical and due to their ease of processing are of potential interest to synthesize as coatings materials for wear and corrosion resistance applications. Fe-Cr-Mo-Y-C-B amorphous system was used to develop thick coatings on 4130 Steel substrate and the corrosion resistance of the amorphous coatings was improved. It is also shown that the mode of corrosion depends on the laser processing

  11. Spatiotemporal kinetics of γ-H2AX protein on charged particles induced DNA damage

    NASA Astrophysics Data System (ADS)

    Niu, H.; Chang, H. C.; Cho, I. C.; Chen, C. H.; Liu, C. S.; Chou, W. T.

    2014-08-01

    In several researches, it has been demonstrated that charged particles can induce more complex DNA damages. These complex damages have higher ability to cause the cell death or cell carcinogenesis. For this reason, clarifying the DNA repair mechanism after charged particle irradiation plays an important role in the development of charged particle therapy and space exploration. Unfortunately, the detail spatiotemporal kinetic of DNA damage repair is still unclear. In this study, we used γ-H2AX protein to investigate the spatiotemporal kinetics of DNA double strand breaks in alpha-particle irradiated HeLa cells. The result shows that the intensity of γ-H2AX foci increased gradually, and reached to its maximum at 30 min after irradiation. A good linear relationship can be observed between foci intensity and radiation dose. After 30 min, the γ-H2AX foci intensity was decreased with time passed, but remained a large portion (∼50%) at 48 h passed. The data show that the dissolution rate of γ-H2AX foci agreed with two components DNA repairing model. These results suggest that charged particles can induce more complex DNA damages and causing the retardation of DNA repair.

  12. Growing timescales and lengthscales characterizing vibrations of amorphous solids

    PubMed Central

    Berthier, Ludovic; Charbonneau, Patrick; Jin, Yuliang; Parisi, Giorgio; Zamponi, Francesco

    2016-01-01

    Low-temperature properties of crystalline solids can be understood using harmonic perturbations around a perfect lattice, as in Debye’s theory. Low-temperature properties of amorphous solids, however, strongly depart from such descriptions, displaying enhanced transport, activated slow dynamics across energy barriers, excess vibrational modes with respect to Debye’s theory (i.e., a boson peak), and complex irreversible responses to small mechanical deformations. These experimental observations indirectly suggest that the dynamics of amorphous solids becomes anomalous at low temperatures. Here, we present direct numerical evidence that vibrations change nature at a well-defined location deep inside the glass phase of a simple glass former. We provide a real-space description of this transition and of the rapidly growing time- and lengthscales that accompany it. Our results provide the seed for a universal understanding of low-temperature glass anomalies within the theoretical framework of the recently discovered Gardner phase transition. PMID:27402768

  13. Self-assembly of amorphous calcium carbonate microlens arrays.

    PubMed

    Lee, Kyubock; Wagermaier, Wolfgang; Masic, Admir; Kommareddy, Krishna P; Bennet, Mathieu; Manjubala, Inderchand; Lee, Seung-Woo; Park, Seung B; Cölfen, Helmut; Fratzl, Peter

    2012-03-06

    Biological materials are often based on simple constituents and grown by the principle of self-assembly under ambient conditions. In particular, biomineralization approaches exploit efficient pathways of inorganic material synthesis. There is still a large gap between the complexity of natural systems and the practical utilization of bioinspired formation mechanisms. Here we describe a simple self-assembly route leading to a CaCO(3) microlens array, somewhat reminiscent of the brittlestars' microlenses, with uniform size and focal length, by using a minimum number of components and equipment at ambient conditions. The formation mechanism of the amorphous CaCO(3) microlens arrays was elucidated by confocal Raman spectroscopic imaging to be a two-step growth process mediated by the organic surfactant. CaCO(3) microlens arrays are easy to fabricate, biocompatible and functional in amorphous or more stable crystalline forms. This shows that advanced optical materials can be generated by a simple mineral precipitation.

  14. Growing timescales and lengthscales characterizing vibrations of amorphous solids

    NASA Astrophysics Data System (ADS)

    Berthier, Ludovic; Charbonneau, Patrick; Jin, Yuliang; Parisi, Giorgio; Seoane, Beatriz; Zamponi, Francesco

    2016-07-01

    Low-temperature properties of crystalline solids can be understood using harmonic perturbations around a perfect lattice, as in Debye’s theory. Low-temperature properties of amorphous solids, however, strongly depart from such descriptions, displaying enhanced transport, activated slow dynamics across energy barriers, excess vibrational modes with respect to Debye’s theory (i.e., a boson peak), and complex irreversible responses to small mechanical deformations. These experimental observations indirectly suggest that the dynamics of amorphous solids becomes anomalous at low temperatures. Here, we present direct numerical evidence that vibrations change nature at a well-defined location deep inside the glass phase of a simple glass former. We provide a real-space description of this transition and of the rapidly growing time- and lengthscales that accompany it. Our results provide the seed for a universal understanding of low-temperature glass anomalies within the theoretical framework of the recently discovered Gardner phase transition.

  15. Anatomy of plastic events in magnetic amorphous solids

    NASA Astrophysics Data System (ADS)

    Hentschel, H. George E.; Procaccia, Itamar; Gupta, Bhaskar Sen

    2016-03-01

    Plastic events in amorphous solids can be much more than just "shear transformation zones" when the positional degrees of freedom are coupled nontrivially to other degrees of freedom. Here we consider magnetic amorphous solids where mechanical and magnetic degrees of freedom interact, leading to rather complex plastic events whose nature must be disentangled. In this paper we uncover the anatomy of the various contributions to some typical plastic events. These plastic events are seen as Barkhausen noise or other "serrated noises." Using theoretical considerations we explain the observed statistics of the various contributions to the considered plastic events. The richness of contributions and their different characteristics imply that in general the statistics of these serrated noises cannot be universal, but rather highly dependent on the state of the system and on its microscopic interactions.

  16. Fluorination of amorphous thin-film materials with xenon fluoride

    DOEpatents

    Weil, R.B.

    1987-05-01

    A method is disclosed for producing fluorine-containing amorphous semiconductor material, preferably comprising amorphous silicon. The method includes depositing amorphous thin-film material onto a substrate while introducing xenon fluoride during the film deposition process.

  17. Fluorination of amorphous thin-film materials with xenon fluoride

    DOEpatents

    Weil, Raoul B.

    1988-01-01

    A method is disclosed for producing fluorine-containing amorphous semiconductor material, preferably comprising amorphous silicon. The method includes depositing amorphous thin-film material onto a substrate while introducing xenon fluoride during the film deposition process.

  18. Imprinting bulk amorphous alloy at room temperature

    DOE PAGES

    Kim, Song-Yi; Park, Eun-Soo; Ott, Ryan T.; ...

    2015-11-13

    We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the abilitymore » of amorphous alloys or metallic glasses to precisely replicate patterning features onto both conventional metals and the other amorphous alloys. In conclusion, our work presents an avenue for avoiding the embrittlement of amorphous alloys associated with thermoplastic forming and yields new insight the forming application of bulk amorphous alloys at room temperature without using heat treatment.« less

  19. Amorphization of solids irradiated by fast neutrons

    NASA Astrophysics Data System (ADS)

    Parkhomenko, V.; Dubinin, S.; Teploukhov, S.; Goshchitskii, B.

    2000-03-01

    The diffraction patterns of amorphous solids produced by both a conventional technique and fast neutron irradiation were systematized. It is shown for the first time that neutron radiation-modified solids belong to the group of amorphous substances of a distortion type.

  20. Evolution of the structure of amorphous ice: from low-density amorphous through high-density amorphous to very high-density amorphous ice.

    PubMed

    Martonák, R; Donadio, D; Parrinello, M

    2005-04-01

    We report results of molecular dynamics simulations of amorphous ice for pressures up to 22.5 kbar. The high-density amorphous ice (HDA) as prepared by pressure-induced amorphization of I(h) ice at T=80 K is annealed to T=170 K at various pressures to allow for relaxation. Upon increase of pressure, relaxed amorphous ice undergoes a pronounced change of structure, ranging from the low-density amorphous ice at p=0, through a continuum of HDA states to the limiting very high-density amorphous ice (VHDA) regime above 10 kbar. The main part of the overall structural change takes place within the HDA megabasin, which includes a variety of structures with quite different local and medium-range order as well as network topology and spans a broad range of densities. The VHDA represents the limit to densification by adapting the hydrogen-bonded network topology, without creating interpenetrating networks. The connection between structure and metastability of various forms upon decompression and heating is studied and discussed. We also discuss the analogy with amorphous and crystalline silica. Finally, some conclusions concerning the relation between amorphous ice and supercooled water are drawn.

  1. Electron beam recrystallization of amorphous semiconductor materials

    NASA Technical Reports Server (NTRS)

    Evans, J. C., Jr.

    1968-01-01

    Nucleation and growth of crystalline films of silicon, germanium, and cadmium sulfide on substrates of plastic and glass were investigated. Amorphous films of germanium, silicon, and cadmium sulfide on amorphous substrates of glass and plastic were converted to the crystalline condition by electron bombardment.

  2. Electron tunnelling into amorphous germanium and silicon.

    NASA Technical Reports Server (NTRS)

    Smith, C. W.; Clark, A. H.

    1972-01-01

    Measurements of tunnel conductance versus bias, capacitance versus bias, and internal photoemission were made in the systems aluminum-oxide-amorphous germanium and aluminium-oxide-amorphous silicon. A function was extracted which expresses the deviation of these systems from the aluminium-oxide-aluminium system.

  3. Method of making amorphous metal composites

    DOEpatents

    Byrne, Martin A.; Lupinski, John H.

    1982-01-01

    The process comprises placing an amorphous metal in particulate form and a low molecular weight (e.g., 1000-5000) thermosetting polymer binder powder into a container, mixing these materials, and applying heat and pressure to convert the mixture into an amorphous metal composite.

  4. Co amorphous systems: A product development perspective.

    PubMed

    Chavan, Rahul B; Thipparaboina, Rajesh; Kumar, Dinesh; Shastri, Nalini R

    2016-12-30

    Solubility is one of the major problems associated with most of the new chemical entities that can be reasonably addressed by drug amorphization. However, being a high-energy form, it usually tends to re-crystallize, necessitating new formulation strategies to stabilize amorphous drugs. Polymeric amorphous solid dispersion (PASD) is one of the widely investigated strategies to stabilize amorphous drug, with major limitations like limited polymer solubility and hygroscopicity. Co amorphous system (CAM), a new entrant in amorphous arena is a promising alternative to PASD. CAMs are multi component single phase amorphous solid systems made up of two or more small molecules that may be a combination of drugs or drug and excipients. Excipients explored for CAM preparation include amino acids, carboxylic acids, nicotinamide and saccharine. Advantages offered by CAM include improved aqueous solubility and physical stability of amorphous drug, with a potential to improve therapeutic efficacy. This review attempts to address different aspects in the development of CAM as drug products. Criterion for co-former selection, various methods involved in CAM preparation, characterization tools, stability, scale up and regulatory requirements for the CAM product development are discussed.

  5. Origin of "memory glass" effect in pressure-amorphized rare-earth molybdate single crystals

    NASA Astrophysics Data System (ADS)

    Willinger, Elena; Sinitsyn, Vitaly; Khasanov, Salavat; Redkin, Boris; Shmurak, Semeon; Ponyatovsky, Eugeny

    2015-02-01

    The memory glass effect (MGE) describes the ability of some materials to recover the initial structure and crystallographic orientation after pressure-induced amorphization (PIA). In spite of numerous studies the nature and underlying mechanisms of this phenomenon are still not clear. Here we report investigations of MGE in β‧-Eu2(MoO4)3 single crystal samples subjected to high pressure amorphization. Using the XRD and TEM techniques we carried out detailed analysis of the structural state of high pressure treated single crystal samples as well as structural transformations due to subsequent annealing at atmospheric pressure. The structure of the sample has been found to be complex, mainly amorphous, however, the amorphous medium contains evenly distributed nanosize inclusions of a paracrystalline phase. The inclusions are highly correlated in orientation and act as "memory units" in the MGE.

  6. Study of excitation functions of alpha-particle induced nuclear reactions on holmium for 167Tm production.

    PubMed

    Tárkányi, F; Hermanne, A; Király, B; Takács, S; Ignatyuk, A V

    2010-03-01

    (167)Tm is a candidate radioisotope for both nuclear medicine diagnostics and therapy due to its emitted Auger-electrons, low energy X- and gamma-rays. In the frame of a systematic study of excitation functions for production of medically relevant radioisotopes by charged particle induced reactions on rare earths, the (165)Ho(alpha,2n)(167)Tm reaction and the (165)Ho(alpha,n)(168)Tm, (165)Ho(alpha,3n)(166)Tm, (165)Ho(alpha,4n)(165)Tm side reactions were measured up to 40 MeV by the stacked foil irradiation technique and gamma-ray spectroscopy. The measured results were compared to the ALICE-IPPE and EMPIRE-II theoretical curves. Thick target yields, impurity levels and specific activities were deduced and compared with the same parameters for other charged particle production routes of (167)Tm. Copyright 2009 Elsevier Ltd. All rights reserved.

  7. Neutron irradiation induced amorphization of silicon carbide

    SciTech Connect

    Snead, L.L.; Hay, J.C.

    1998-09-01

    This paper provides the first known observation of silicon carbide fully amorphized under neutron irradiation. Both high purity single crystal hcp and high purity, highly faulted (cubic) chemically vapor deposited (CVD) SiC were irradiated at approximately 60 C to a total fast neutron fluence of 2.6 {times} 10{sup 25} n/m{sup 2}. Amorphization was seen in both materials, as evidenced by TEM, electron diffraction, and x-ray diffraction techniques. Physical properties for the amorphized single crystal material are reported including large changes in density ({minus}10.8%), elastic modulus as measured using a nanoindentation technique ({minus}45%), hardness as measured by nanoindentation ({minus}45%), and standard Vickers hardness ({minus}24%). Similar property changes are observed for the critical temperature for amorphization at this neutron dose and flux, above which amorphization is not possible, is estimated to be greater than 130 C.

  8. Structure, thermodynamics, and crystallization of amorphous hafnia

    SciTech Connect

    Luo, Xuhui; Demkov, Alexander A.

    2015-09-28

    We investigate theoretically amorphous hafnia using the first principles melt and quench method. We identify two types of amorphous structures of hafnia. Type I and type II are related to tetragonal and monoclinic hafnia, respectively. We find type II structure to show stronger disorder than type I. Using the phonon density of states, we calculate the specific heat capacity for type II amorphous hafnia. Using the nudged elastic band method, we show that the averaged transition barrier between the type II amorphous hafnia and monoclinic phase is approximately 0.09 eV/HfO{sub 2}. The crystallization temperature is estimated to be 421 K. The calculations suggest an explanation for the low thermal stability of amorphous hafnia.

  9. Amorphization of sugar hydrates upon milling.

    PubMed

    Willart, J F; Dujardin, N; Dudognon, E; Danède, F; Descamps, M

    2010-07-19

    The possibility to amorphize anhydrous crystalline sugars, like lactose, trehalose and glucose, by mechanical milling was previously reported. We test here the possibility to amorphize the corresponding crystalline hydrates: lactose monohydrate, trehalose dihydrate and glucose monohydrate using fully identical milling procedures. The results show that only the first hydrate amorphizes while the other two remain structurally invariant. These different behaviours are attributed to the plasticizing effect of the structural water molecules which can decrease the glass transition temperature below the milling temperature. The results reveal clearly the fundamental role of the glass transition in the solid-state amorphization process induced by milling, and they also explain why crystalline hydrates are systematically more difficult to amorphize by milling than their anhydrous counterpart. The investigations have been performed by differential scanning calorimetry and powder X-ray diffraction.

  10. Compensated amorphous-silicon solar cell

    DOEpatents

    Devaud, G.

    1982-06-21

    An amorphous silicon solar cell including an electrically conductive substrate, a layer of glow discharge deposited hydrogenated amorphous silicon having regions of differing conductivity with at least one region of intrinsic hydrogenated amorphous silicon. The layer of hydrogenated amorphous silicon has opposed first and second major surfaces where the first major surface contacts the elecrically conductive substrate and an electrode for electrically contacting the second major surface. The intrinsic hydrogenated amorphous silicon region is deposited in a glow discharge with an atmosphere which includes not less than about 0.02 atom percent mono-atomic boron. An improved N.I.P. solar cell is disclosed using a BF/sub 3/ doped intrinsic layer.

  11. Role of diffusion in amorphous-phase formation and crystallization of amorphous Ni--Zr

    SciTech Connect

    Barbour, J.C.; de Reus, R.; Denier van der Gon, A.W.; Saris, F.W.

    1987-03-01

    The Ni--Zr system is examined as a representative system for the formation of an amorphous phase by diffusion and for the crystallization of an amorphous phase by diffusion. High-resolution electron microscopy (HREM) is used to show that the amorphous phase grows by bulk diffusion through the amorphous material rather than by short-circuit diffusion. Also, the HREM shows that the amorphous phase formed by diffusion appears to be the same as the vapor-deposited amorphous phase. A correlation between crystallization temperatures (T/sub x/) and the enthalpy of large-atom hole formation is given. This correlation predicts values of T/sub x/ that are lower than those predicted from the small-atom hole-formation model. The difference in hole-formation enthalpies for the large and small atoms is given as a criterion for amorphous-phase formation via diffusion.

  12. Toxicity of Mineral Dusts and a Proposed Mechanism for the Pathogenesis of Particle-Induced Lung Diseases

    NASA Technical Reports Server (NTRS)

    Lam, Chiu-wing; James, John T.; Zhang, Ye; Scully, Robert R.; Hunter, Robert; Zeidler-Erdely, Patti C.; Castranova, Vincent

    2017-01-01

    The mechanism of particle-induced lung pathology is still poorly understood. Neutrophilic inflammation and oxidative stress (OS) are toxicological hallmarks in the lungs of dust-exposed animals. Some investigators attribute OS-induced pathogenicity to particle surface reactivity (SR) or free radicals generated by dusts. Using 5 dusts (3 lunar dusts [LDs], quartz, and TiO2) that differed 18-fold in SR, we showed that the SRs of particles did not correlate with the dusts' toxicities in the lung; aged-quartz had the lowest SR, but was most toxic (Lam et al. 2015). Thus, OS must come from endogenous sources, which is the subject of this follow-up investigation and review. In our 5-dust instillation study and LD-inhalation study in rats, we observed not only dose-dependent increases in neutrophils in the bronchoalveolar lavage fluids, but also dose- and time-dependent increases in oxidative content per neutrophil, which have not been reported by others. The neutrophil counts and oxidant content per cell parallel the cytotoxicity and pulmonary pathology of these dusts (quartz greater than LD greater than TiO2). Our data and those of others allow us to postulate a general mechanism for the pathogenesis of particle-induced pulmonary diseases that involves persistent infiltration of neutrophils; postmortem oxidant-release from these short-lived neutrophils provides a prolonged source of endogenous OS in the lungs. This mechanism explains why one dust (e.g., quartz or nanoparticles) is more toxic than another (e.g., micrometer-sized TiO2); why dust-induced lesions progress with time; and why lung cancer occurs in rats but not in mice and hamsters exposed to the same dust under the same exposure-regime.

  13. Locomotion of Amorphous Surface Robots

    NASA Technical Reports Server (NTRS)

    Bradley, Arthur T. (Inventor)

    2016-01-01

    An amorphous robot includes a compartmented bladder containing fluid, a valve assembly, and an outer layer encapsulating the bladder and valve assembly. The valve assembly draws fluid from a compartment(s) and discharges the drawn fluid into a designated compartment to displace the designated compartment with respect to the surface. Another embodiment includes elements each having a variable property, an outer layer that encapsulates the elements, and a control unit. The control unit energizes a designated element to change its variable property, thereby moving the designated element. The elements may be electromagnetic spheres with a variable polarity or shape memory polymers with changing shape and/or size. Yet another embodiment includes an elongated flexible tube filled with ferrofluid, a moveable electromagnet, an actuator, and a control unit. The control unit energizes the electromagnet and moves the electromagnet via the actuator to magnetize the ferrofluid and lengthen the flexible tube.

  14. Locomotion of Amorphous Surface Robots

    NASA Technical Reports Server (NTRS)

    Bradley, Arthur T. (Inventor)

    2014-01-01

    An amorphous robot includes a compartmented bladder containing fluid, a valve assembly, and an outer layer encapsulating the bladder and valve assembly. The valve assembly draws fluid from a compartment(s) and discharges the drawn fluid into a designated compartment to displace the designated compartment with respect to the surface. Another embodiment includes elements each having a variable property, an outer layer that encapsulates the elements, and a control unit. The control unit energizes a designated element to change its variable property, thereby moving the designated element. The elements may be electromagnetic spheres with a variable polarity or shape memory polymers with changing shape and/or size. Yet another embodiment includes an elongated flexible tube filled with ferrofluid, a moveable electromagnet, an actuator, and a control unit. The control unit energizes the electromagnet and moves the electromagnet via the actuator to magnetize the ferrofluid and lengthen the flexible tube.

  15. Biologically formed amorphous calcium carbonate.

    PubMed

    Weiner, Steve; Levi-Kalisman, Yael; Raz, Sefi; Addadi, Lia

    2003-01-01

    Many organisms from a wide variety of taxa produce amorphous calcium carbonate (ACC), despite the fact that it is inherently unstable and relatively soluble in its pure state. These properties also make it difficult to detect and characterize ACC. Raman spectroscopy is a particularly useful method for investigating ACC because the sample can be examined wet, and extended X-ray absorption fine structure (EXAFS) analysis can provide detailed information on the short-range order. Other methods for characterizing ACC include infrared spectroscopy, thermogravimetric analysis and differential thermal analysis (TGA and DTA), transmission electron microscopy (TEM), and electron and X-ray diffraction. Because of the difficulties involved, we suspect that ACC is far more widely distributed than is presently known, and a comparison of EXAFS spectra shows that different biogenic ACC phases have different short-range order structures. We also suspect that ACC fulfils many different functions, including as a transient precursor phase during the formation of crystalline calcium carbonate.

  16. Comparative analysis of urban atmospheric aerosol by particle-induced X-ray emission (PIXE), proton elastic scattering analysis (PESA), and aerosol mass spectrometry (AMS).

    PubMed

    Johnson, K S; Laskin, A; Jimenez, J L; Shutthanandan, V; Molina, L T; Salcedo, D; Dzepina, K; Molina, M J

    2008-09-01

    A multifaceted approach to atmospheric aerosol analysis is often desirable in field studies where an understanding of technical comparability among different measurement techniques is essential. Herein, we report quantitative intercomparisons of particle-induced X-ray emission (PIXE) and proton elastic scattering analysis (PESA), performed of fline under a vacuum, with analysis by aerosol mass spectrometry (AMS) carried out in real-time during the MCMA-2003 Field Campaign in the Mexico City Metropolitan Area. Good agreement was observed for mass concentrations of PIXE-measured sulfur (assuming it was dominated by SO4(2-)) and AMS-measured sulfate during most of the campaign. PESA-measured hydrogen mass was separated into sulfate H and organic H mass fractions, assuming the only major contributions were (NH4)2SO4 and organic compounds. Comparison of the organic H mass with AMS organic aerosol measurements indicates that about 75% of the mass of these species evaporated under a vacuum. However approximately 25% of the organics does remain under a vacuum, which is only possible with low-vapor-pressure compounds, and which supports the presence of high-molecular-weight or highly oxidized organics consistent with atmospheric aging. Approximately 10% of the chloride detected by AMS was measured by PIXE, possibly in the form of metal-chloride complexes, while the majority of Cl was likely present as more volatile species including NH4Cl. This is the first comparison of PIXE/PESA and AMS and, to our knowledge, also the first report of PESA hydrogen measurements for urban organic aerosols.

  17. Characterisation of ferromagnetic magnetic storage media surfaces by complementary particle induced X-ray analysis and time of flight-energy dispersive elastic recoil detection analysis

    NASA Astrophysics Data System (ADS)

    Zhang, Yanwen; Elfman, Mikael; Winzell, Thomas; Whitlow, Harry J.

    1999-04-01

    Thin (10 nm-1 μm) films of ferromagnetic material constitute an important class of materials that are difficult to analyse by conventional ion beam analytical (IBA) techniques because they are based on the ferromagnetic elements (Co, Fe, Mn, Ni, and Cr). The similar or overlapping isotope masses makes it difficult to separate the elemental signals using time of flight and energy dispersive elastic recoil detection (ToF-E ERD). In this exploratory study we have investigated the use of Particle Induced X-ray Emission (PIXE) measurements to refine the mass dispersive depth profile information from ToF-E ERD. The surfaces of two commercial magnetic media were investigated. One sample was a 3 {1}/{2}'' double density diskette with a coating of ferrite particles in an organic binder. The other sample was a complex C/Co/Cr/Ni-P/Al multilayer structure taken from a standard hard disc. The Lund nuclear microprobe with a 2.55 MeV proton beam was used for PIXE analysis. ToF-ERD measurements were carried out using a 55 MeV 127I 10+ ion beam incident at 67.5° to the surface normal. The time of flight and kinetic energy of recoils ejected at 45° to the ion beam direction was measured in a detector telescope. The findings demonstrate that by detailed analysis of the PIXE spectra it is possible to remove the ambiguities in mass assignment of the ToF-ERD data associated with the ferromagnetic elements.

  18. Crystalline to amorphous transformation in silicon

    SciTech Connect

    Cheruvu, S.M.

    1982-09-01

    In the present investigation, an attempt was made to understand the fundamental mechanism of crystalline-to-amorphous transformation in arsenic implanted silicon using high resolution electron microscopy. A comparison of the gradual disappearance of simulated lattice fringes with increasing Frenkel pair concentration with the experimental observation of sharp interfaces between crystalline and amorphous regions was carried out leading to the conclusion that when the defect concentration reaches a critical value, the crystal does relax to an amorphous state. Optical diffraction experiments using atomic models also supported this hypothesis. Both crystalline and amorphous zones were found to co-exist with sharp interfaces at the atomic level. Growth of the amorphous fraction depends on the temperature, dose rate and the mass of the implanted ion. Preliminary results of high energy electron irradiation experiments at 1.2 MeV also suggested that clustering of point defects occurs near room temperature. An observation in a high resolution image of a small amorphous zone centered at the core of a dislocation is presented as evidence that the nucleation of an amorphous phase is heterogeneous in nature involving clustering or segregation of point defects near existing defects.

  19. Microwave Switching in Amorphous-Carbon Quantum Wells

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Somnath; Gomez Rojas, Luis; Silva, S. Ravi. P.

    2007-03-01

    Demonstration of long phase coherence length showing resonant tunnelling and fast switching in amorphous carbon quantum well structures has recently been established [1]. Here we show a bias controlled reversible switching of the complex impedance by transmitting a microwave signal up to 110GHz through amorphous carbon resonant tunnel diodes. By employing a coplanar waveguide technique and through the analysis of the return loss (S11) microwave enhanced mobility greater than 30cm^2(Vs)-1 in the delocalized regime of (filamentary) conduction in these devices is demonstrated. Also a switching behaviour at about 85GHz can also be observed. We suggest a new model for the microscopic origin of the increased mobility and show routes to achieve longer coherence lengths. In addition microwave conductance of carbon quantum wells parallel to their plane and across a channel length larger than 100 nm determines the momentum scattering time of electrons in carbon. These results exhibit a potential for pure amorphous carbon-based fast memory devices. [1] S. Bhattacharyya, S.J. Henley, E. Mendoza, L. Gomez Rojas, J. Allam and S.R.P. Silva, Nature Mater. 5, 19 (2006).

  20. Origin of Magnetic Properties in Amorphous Metals.

    DTIC Science & Technology

    1979-12-01

    Magnetic Properties of Fe-Ni-B Amorphous Alloys," F. E. Luborsky, J. L. Walter, and H. H. Liebermann , IEEE Trans. on Magnetics MAG-15, 909 (1979). Also GE...Report 78CRD132. 2. "Formation and Magnetic Properties of Fe-B-Si Amorphous Alloys," F. E. Luborsky, J. J. Becker, J. L. Walter, and H. H. Liebermann ...Amorphous Alloys," F. E. Luborsky and H. H. Liebermann , J. Appl. Phys., to appear. Also GE Report 79CRD177. 4. "The Effect of Temperature on Magnetic

  1. Characterization of mechanical heterogeneity in amorphous solids

    NASA Astrophysics Data System (ADS)

    Peng, H. L.; Li, M. Z.; Sun, B. A.; Wang, W. H.

    2012-07-01

    The structural geometry and size distribution of the local atomic rearrangements induced by external stress in amorphous solids are investigated by molecular dynamics studies. We find that the size distribution exhibits a generic power-law behavior and their structural geometry shows fractal feature. This indicates that the local atomic rearrangements in amorphous solids are self-organized during deformation. A simple theoretical model based on the interaction of the heterogeneous elastic field sources is proposed which predicts the power-law scaling and characterizes the properties of the local atomic rearrangements in amorphous solids.

  2. Laser irradiation to produce amorphous pharmaceuticals.

    PubMed

    Titapiwatanakun, Varin; Tankul, Junlathip; Basit, Abdul W; Gaisford, Simon

    2016-11-30

    Using a high-power CO2 laser to irradiate powder beds, it was possible to induce phase transformation to the amorphous state. Irradiation of a model drug, indometacin, resulted in formation of a glass. Varying the settings of the laser (power and raster speed) was shown to change the physicochemical properties of the glasses produced and all irradiated glasses were found to be more stable than a reference glass produced by melt-quenching. Irradiation of a powder blend of paracetamol and polyvinylpyrrolidone K30 was found to produce a solid amorphous dispersion. The results suggest that laser-irradiation might be a useful method for making amorphous pharmaceuticals.

  3. Photonic crystals, amorphous materials, and quasicrystals.

    PubMed

    Edagawa, Keiichi

    2014-06-01

    Photonic crystals consist of artificial periodic structures of dielectrics, which have attracted much attention because of their wide range of potential applications in the field of optics. We may also fabricate artificial amorphous or quasicrystalline structures of dielectrics, i.e. photonic amorphous materials or photonic quasicrystals. So far, both theoretical and experimental studies have been conducted to reveal the characteristic features of their optical properties, as compared with those of conventional photonic crystals. In this article, we review these studies and discuss various aspects of photonic amorphous materials and photonic quasicrystals, including photonic band gap formation, light propagation properties, and characteristic photonic states.

  4. Photonic crystals, amorphous materials, and quasicrystals

    PubMed Central

    Edagawa, Keiichi

    2014-01-01

    Photonic crystals consist of artificial periodic structures of dielectrics, which have attracted much attention because of their wide range of potential applications in the field of optics. We may also fabricate artificial amorphous or quasicrystalline structures of dielectrics, i.e. photonic amorphous materials or photonic quasicrystals. So far, both theoretical and experimental studies have been conducted to reveal the characteristic features of their optical properties, as compared with those of conventional photonic crystals. In this article, we review these studies and discuss various aspects of photonic amorphous materials and photonic quasicrystals, including photonic band gap formation, light propagation properties, and characteristic photonic states. PMID:27877676

  5. Amorphous to Amorphous Form Transitions of Water Ice and Astrophysical Implications

    NASA Technical Reports Server (NTRS)

    Jenniskens, Peter; Blake, David F.; Chang, Sherwood (Technical Monitor)

    1994-01-01

    We have combined Selected Area Electron Diffraction (SAED) and cryogenic techniques in an instrumental configuration that allows observing the structure of vapor deposited ice as it evolves during warmup. The ice is deposited in-situ inside an Hitachi H-500 H transmission electron microscope at a base pressure of 1-5 x 10(exp -7) torr on a thin amorphous carbon substrate at 15K or 86K and warmed up at a rate of 1-2 K/min. We find a progression of amorphous forms and well defined amorphous to amorphous transitions. Apart from the well known low-density form of ice, we confirm the presence of a high-density form and find a third amorphous form that coexists with cubic ice. We will report too on the amorphous to crystalline transition and the implications of these results for radical diffusion and gas retention observed in laboratory analog studies of interstellar and cometary ices.

  6. Microwave absorption properties of amorphous iron nanostructures fabricated by a high-yield method

    NASA Astrophysics Data System (ADS)

    Wang, Zhen; Zuo, Yalu; Yao, Yuelin; Xi, Li; Du, Jihong; Wang, Jianbo; Xue, Desheng

    2013-04-01

    Amorphous Fe nanoparticles and a nanonecklace were synthesized at room temperature by an aqueous reduction procedure, which provided a simple and potential method for volume production of ferromagnetic materials. The morphology was examined by scanning electron microscopy and transmission electron microscopy. The amorphism of Fe nanoparticles and the nanonecklace was confirmed by x-ray diffraction and electron diffraction patterns in transmission electron microscopy. The complex permittivity and permeability behaviour of amorphous iron nanoparticles/paraffin wax (NPPW) and nanonecklace/paraffin wax (NCPW) composites was investigated in 0.1-18 GHz by a coaxial method. The strongest reflection loss values of NPPW and NCPW calculated from permittivity and permeability reached -53.2 dB and -47.8 dB at 6.4 GHz and 4.6 GHz with matching thicknesses of 2.4 mm and 2.3 mm, respectively. Moreover, the frequency ranges of microwave absorption exceeding 90% were around 4.9-8.8 GHz and 3.7-6.1 GHz for NPPW and NCPW, respectively. Comparing the microwave absorption property with crystallized Fe nanostructures, we may conclude that the relatively high resistivity and low permittivity of amorphous Fe nanostructures are favourable for impedance matching, and consequently result in the attracting microwave absorption property of amorphous Fe nanostructures. Thus, amorphous iron nanoparticles and the nanonecklace prepared by a high-yield method have great potential to be a highly efficient microwave absorber.

  7. Synthesis of adenosine triphosphate in respiration-inhibited submitochondrial particles induced by microsecond electric pulses

    PubMed Central

    Teissie, Justin; Knox, Barry E.; Tsong, Tian Yow; Wehrle, Janna

    1981-01-01

    Phosphorylation of ADP to ATP was induced in nonrespiring submitochondrial particles (SMP) from rat liver by the application of electric pulses with field strengths of 10-35 kV/cm and a decay time of 60 μs. In all cases respiration was inhibited completely by using cyanide or rotenone. Newly formed ATP was measured by two independent methods, (i) the luciferase/luciferin bioluminescence assay and (ii) synthesis of [32P]ATP from ADP and 32Pi. Both methods gave consistent and essentially identical results. Above 10 kV/cm the amount of ATP synthesized increased with increasing field strength, and at 30 kV/cm, approximately 40 pmol of ATP was synthesized per mg of SMP protein per pulse. ATP synthesis was shown to be related to the field-induced transmembrane potential, not to Joule heating of the suspension. Synthesis was abolished by the uncouplers carbonyl cyanide p-trifluoromethoxyphenylhydrazone, carbonyl cyanide m-chlorophenylhydrazone, and 2,4-dinitrophenol. The ionophores valinomycin and A23187 reduced the level of synthesis by 75% and 50%, respectively. ATP synthesis was also blocked by inhibitors of the F0F1 ATPase complex, oligomycin, N,N′-dicyclohexyl carbodiimide, venturicidin, and aurovertin. The activities of the adenine nucleotide translocator and adenylate kinase, as well as release of bound nucleotides, could be excluded as sources of the new ATP. The data indicate that the minimal applied field at which ATP synthesis could be detected is approximately 8 kV/cm, corresponding to a maximal induced membrane potential of 60 mV in SMP. The maximal synthesis occurred at around 30 kV/cm, or an induced transmembrane potential of 200 mV. The duration of the applied pulse was also found to be critical, with 8 μs being the minimal triggering time for the synthesis. The induction of ATP synthesis in nonrespiring SMP by an externally applied electrical field is a direct demonstration of the transformation, by the mitochondrial inner membrane, of electrical

  8. The contribution of vapor deposition to amorphous rims on lunar soil grains. [Abstract only

    NASA Technical Reports Server (NTRS)

    Keller, L. P.; Mckay, D. S.

    1994-01-01

    Recent analysis analytical electron microscope study of lunar soils showed that the approximately 60-nm-wide amorphous rims surrounding many lunar soils grains exhibit distinct compositional differences from their hosts. On average, the amorphous rim compositions reflect the local bulk soil composition with the exceptions of Si and S, which are enriched relative to the bulk soil. These chemical trends led us to propose that the amorphous rims were in fact deposits of impact-generated vapors produced during regolith gardening, a hypothesis that runs contrary to the generally accepted view that the rims are produced through amorphization of the outer parts of mineral grains by interaction with the solar wind. Analytical data are reported for amorphous rims on individual minerals in lunar soils in order to show that the magnitude of the chemical differences between rim and host are so great that they require a major addition of foreign elements to the grain surfaces. The average composition of amorphous rims is listed as a function of host mineralogy as determined in microtone thin sections using energy-dispersive X-ray spectrometry in the transmission electron microscope. As the host mineral becomes chemically more complex, the chemical differences are not as clear. The average rim compositions are remarkably similar and are independent of the host grain mineralogy. Whether there are 'sputtering' or radiation effects superimposed on the vapor-deposited material can be debated. We do not explicitly exclude the effects of radiation damage as a contributing factor to the formation of amorphous rims; we are merely emphasizing the major role played by condensed vapors in the formation of amorphous rims on lunar soil grains.

  9. Corrosion resistant amorphous metals and methods of forming corrosion resistant amorphous metals

    DOEpatents

    Farmer, Joseph C.; Wong, Frank M. G.; Haslam, Jeffery J.; Yang, Nancy; Lavernia, Enrique J.; Blue, Craig A.; Graeve, Olivia A.; Bayles, Robert; Perepezko, John H.; Kaufman, Larry; Schoenung, Julie; Ajdelsztajn, Leo

    2009-11-17

    A system for coating a surface comprises providing a source of amorphous metal, providing ceramic particles, and applying the amorphous metal and the ceramic particles to the surface by a spray. The coating comprises a composite material made of amorphous metal that contains one or more of the following elements in the specified range of composition: yttrium (.gtoreq.1 atomic %), chromium (14 to 18 atomic %), molybdenum (.gtoreq.7 atomic %), tungsten (.gtoreq.1 atomic %), boron (.ltoreq.5 atomic %), or carbon (.gtoreq.4 atomic %).

  10. Corrosion resistant amorphous metals and methods of forming corrosion resistant amorphous metals

    DOEpatents

    Farmer, Joseph C.; Wong, Frank M.G.; Haslam, Jeffery J.; Yang, Nancy; Lavernia, Enrique J.; Blue, Craig A.; Graeve, Olivia A.; Bayles, Robert; Perepezko, John H.; Kaufman, Larry; Schoenung, Julie; Ajdelsztajn, Leo

    2014-07-15

    A system for coating a surface comprises providing a source of amorphous metal, providing ceramic particles, and applying the amorphous metal and the ceramic particles to the surface by a spray. The coating comprises a composite material made of amorphous metal that contains one or more of the following elements in the specified range of composition: yttrium (.gtoreq.1 atomic %), chromium (14 to 18 atomic %), molybdenum (.gtoreq.7 atomic %), tungsten (.gtoreq.1 atomic %), boron (.ltoreq.5 atomic %), or carbon (.gtoreq.4 atomic %).

  11. Amorphization of Silicon Carbide by Carbon Displacement

    SciTech Connect

    Devanathan, Ram; Gao, Fei; Weber, William J.

    2004-05-10

    We have used molecular dynamics simulations to examine the possibility of amorphizing silicon carbide (SiC) by exclusively displacing C atoms. At a defect generation corresponding to 0.2 displacements per atom, the enthalpy surpasses the level of melt-quenched SiC, the density decreases by about 15%, and the radial distribution function shows a lack of long-range order. Prior to amorphization, the surviving defects are mainly C Frenkel pairs (67%), but Si Frenkel pairs (18%) and anti-site defects (15%) are also present. The results indicate that SiC can be amorphized by C sublattice displacements. Chemical short-range disorder, arising mainly from interstitial production, plays a significant role in the amorphization.

  12. Amorphous Phases on the Surface of Mars

    NASA Technical Reports Server (NTRS)

    Rampe, E. B.; Morris, R. V.; Ruff, S. W.; Horgan, B.; Dehouck, E.; Achilles, C. N.; Ming, D. W.; Bish, D. L.; Chipera, S. J.

    2014-01-01

    Both primary (volcanic/impact glasses) and secondary (opal/silica, allophane, hisingerite, npOx, S-bearing) amorphous phases appear to be major components of martian surface materials based on orbital and in-situ measurements. A key observation is that whereas regional/global scale amorphous components include altered glass and npOx, local scale amorphous phases include hydrated silica/opal. This suggests widespread alteration at low water-to-rock ratios, perhaps due to snow/ice melt with variable pH, and localized alteration at high water-to-rock ratios. Orbital and in-situ measurements of the regional/global amorphous component on Mars suggests that it is made up of at least three phases: npOx, amorphous silicate (likely altered glass), and an amorphous S-bearing phase. Fundamental questions regarding the composition and the formation of the regional/global amorphous component(s) still remain: Do the phases form locally or have they been homogenized through aeolian activity and derived from the global dust? Is the parent glass volcanic, impact, or both? Are the phases separate or intimately mixed (e.g., as in palagonite)? When did the amorphous phases form? To address the question of source (local and/or global), we need to look for variations in the different phases within the amorphous component through continued modeling of the chemical composition of the amorphous phases in samples from Gale using CheMin and APXS data. If we find variations (e.g., a lack of or enrichment in amorphous silicate in some samples), this may imply a local source for some phases. Furthermore, the chemical composition of the weathering products may give insight into the formation mechanisms of the parent glass (e.g., impact glasses contain higher Al and lower Si [30], so we might expect allophane as a weathering product of impact glass). To address the question of whether these phases are separate or intimately mixed, we need to do laboratory studies of naturally altered samples made

  13. Ion-beam amorphization of semiconductors: A physical model based on the amorphous pocket population

    SciTech Connect

    Mok, K.R.C.; Jaraiz, M.; Martin-Bragado, I.; Rubio, J.E.; Castrillo, P.; Pinacho, R.; Barbolla, J.; Srinivasan, M.P.

    2005-08-15

    We introduce a model for damage accumulation up to amorphization, based on the ion-implant damage structures commonly known as amorphous pockets. The model is able to reproduce the silicon amorphous-crystalline transition temperature for C, Si, and Ge ion implants. Its use as an analysis tool reveals an unexpected bimodal distribution of the defect population around a characteristic size, which is larger for heavier ions. The defect population is split in both size and composition, with small, pure interstitial and vacancy clusters below the characteristic size, and amorphous pockets with a balanced mixture of interstitials and vacancies beyond that size.

  14. Using containerless methods to develop amorphous pharmaceuticals.

    PubMed

    Weber, J K R; Benmore, C J; Suthar, K J; Tamalonis, A J; Alderman, O L G; Sendelbach, S; Kondev, V; Yarger, J; Rey, C A; Byrn, S R

    2017-01-01

    Many pipeline drugs have low solubility in their crystalline state and require compounding in special dosage forms to increase bioavailability for oral administration. The use of amorphous formulations increases solubility and uptake of active pharmaceutical ingredients. These forms are rapidly gaining commercial importance for both pre-clinical and clinical use. Synthesis of amorphous drugs was performed using an acoustic levitation containerless processing method and spray drying. The structure of the products was investigated using in-situ high energy X-ray diffraction. Selected solvents for processing drugs were investigated using acoustic levitation. The stability of amorphous samples was measured using X-ray diffraction. Samples processed using both spray drying and containerless synthesis were compared. We review methods for making amorphous pharmaceuticals and present data on materials made by containerless processing and spray drying. It was shown that containerless processing using acoustic levitation can be used to make phase-pure forms of drugs that are known to be difficult to amorphize. The stability and structure of the materials was investigated in the context of developing and making clinically useful formulations. Amorphous compounds are emerging as an important component of drug development and for the oral delivery of drugs with low solubility. Containerless techniques can be used to efficiently synthesize small quantities of pure amorphous forms that are potentially useful in pre-clinical trials and for use in the optimization of clinical products. Developing new pharmaceutical products is an essential enterprise to improve patient outcomes. The development and application of amorphous pharmaceuticals to increase absorption is rapidly gaining importance and it provides opportunities for breakthrough research on new drugs. There is an urgent need to solve problems associated with making formulations that are both stable and that provide high

  15. A Magnetic Sensor with Amorphous Wire

    PubMed Central

    He, Dongfeng; Shiwa, Mitsuharu

    2014-01-01

    Using a FeCoSiB amorphous wire and a coil wrapped around it, we have developed a sensitive magnetic sensor. When a 5 mm long amorphous wire with the diameter of 0.1 mm was used, the magnetic field noise spectrum of the sensor was about 30 pT/√Hz above 30 Hz. To show the sensitivity and the spatial resolution, the magnetic field of a thousand Japanese yen was scanned with the magnetic sensor. PMID:24940865

  16. Picosecond Electronic Relaxations In Amorphous Semiconductors

    NASA Astrophysics Data System (ADS)

    Tauc, Jan

    1983-11-01

    Using the pump and probe technique the relaxation processes of photogenerated carriers in amorphous tetrahedral semiconductors and chalcogenide glasses in the time domain from 0.5 Ps to 1.4 ns have been studied. The results obtained on the following phenomena are reviewed: hot carrier thermalization in amorphous silicon; trapping of carriers in undoped a-Si:H; trapping of carriers in deep traps produced by doping; geminate recombination in As2S3-xSex glasses.

  17. Tests Of Amorphous-Silicon Photovoltaic Modules

    NASA Technical Reports Server (NTRS)

    Ross, Ronald G., Jr.

    1988-01-01

    Progress in identification of strengths and weaknesses of amorphous-silicon technology detailed. Report describes achievements in testing reliability of solar-power modules made of amorphous-silicon photovoltaic cells. Based on investigation of modules made by U.S. manufacturers. Modules subjected to field tests, to accelerated-aging tests in laboratory, and to standard sequence of qualification tests developed for modules of crystalline-silicon cells.

  18. Amorphous Carbon-Boron Nitride Nanotube Hybrids

    NASA Technical Reports Server (NTRS)

    Kim, Jae Woo (Inventor); Siochi, Emilie J. (Inventor); Wise, Kristopher E. (Inventor); Lin, Yi (Inventor); Connell, John (Inventor)

    2016-01-01

    A method for joining or repairing boron nitride nanotubes (BNNTs). In joining BNNTs, the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures. In repairing BNNTs, the damaged site of the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures at the damage site.

  19. Opposite correlations between cation disordering and amorphization resistance in spinels versus pyrochlores

    SciTech Connect

    Uberuaga, Blas Pedro; Tang, Ming; Jiang, Chao; Valdez, James A.; Smith, Roger; Wang, Yongqiang; Sickafus, Kurt E.

    2015-10-29

    Understanding and predicting radiation damage evolution in complex materials is crucial for developing next-generation nuclear energy sources. Here, using a combination of ion beam irradiation, transmission electron microscopy and X-ray diffraction, we show that, contrary to the behaviour observed in pyrochlores, the amorphization resistance of spinel compounds correlates directly with the energy to disorder the structure. Using a combination of atomistic simulation techniques, we ascribe this behaviour to structural defects on the cation sublattice that are present in spinel but not in pyrochlore. Specifically, because of these structural defects, there are kinetic pathways for the relaxation of disorder in spinel that are absent in pyrochlore. This leads to a direct correlation between amorphization resistance and disordering energetics in spinel, the opposite of that observed in pyrochlores. Furthermore, these results provide new insight into the origins of amorphization resistance in complex oxides beyond fluorite derivatives.

  20. Opposite correlations between cation disordering and amorphization resistance in spinels versus pyrochlores

    DOE PAGES

    Uberuaga, Blas Pedro; Tang, Ming; Jiang, Chao; ...

    2015-10-29

    Understanding and predicting radiation damage evolution in complex materials is crucial for developing next-generation nuclear energy sources. Here, using a combination of ion beam irradiation, transmission electron microscopy and X-ray diffraction, we show that, contrary to the behaviour observed in pyrochlores, the amorphization resistance of spinel compounds correlates directly with the energy to disorder the structure. Using a combination of atomistic simulation techniques, we ascribe this behaviour to structural defects on the cation sublattice that are present in spinel but not in pyrochlore. Specifically, because of these structural defects, there are kinetic pathways for the relaxation of disorder in spinelmore » that are absent in pyrochlore. This leads to a direct correlation between amorphization resistance and disordering energetics in spinel, the opposite of that observed in pyrochlores. Furthermore, these results provide new insight into the origins of amorphization resistance in complex oxides beyond fluorite derivatives.« less

  1. Opposite correlations between cation disordering and amorphization resistance in spinels versus pyrochlores

    PubMed Central

    Uberuaga, Blas Pedro; Tang, Ming; Jiang, Chao; Valdez, James A.; Smith, Roger; Wang, Yongqiang; Sickafus, Kurt E.

    2015-01-01

    Understanding and predicting radiation damage evolution in complex materials is crucial for developing next-generation nuclear energy sources. Here, using a combination of ion beam irradiation, transmission electron microscopy and X-ray diffraction, we show that, contrary to the behaviour observed in pyrochlores, the amorphization resistance of spinel compounds correlates directly with the energy to disorder the structure. Using a combination of atomistic simulation techniques, we ascribe this behaviour to structural defects on the cation sublattice that are present in spinel but not in pyrochlore. Specifically, because of these structural defects, there are kinetic pathways for the relaxation of disorder in spinel that are absent in pyrochlore. This leads to a direct correlation between amorphization resistance and disordering energetics in spinel, the opposite of that observed in pyrochlores. These results provide new insight into the origins of amorphization resistance in complex oxides beyond fluorite derivatives. PMID:26510750

  2. Thermal transport in amorphous materials: a review

    NASA Astrophysics Data System (ADS)

    Wingert, Matthew C.; Zheng, Jianlin; Kwon, Soonshin; Chen, Renkun

    2016-11-01

    Thermal transport plays a crucial role in performance and reliability of semiconductor electronic devices, where heat is mainly carried by phonons. Phonon transport in crystalline semiconductor materials, such as Si, Ge, GaAs, GaN, etc, has been extensively studied over the past two decades. In fact, study of phonon physics in crystalline semiconductor materials in both bulk and nanostructure forms has been the cornerstone of the emerging field of ‘nanoscale heat transfer’. On the contrary, thermal properties of amorphous materials have been relatively less explored. Recently, however, a growing number of studies have re-examined the thermal properties of amorphous semiconductors, such as amorphous Si. These studies, which included both computational and experimental work, have revealed that phonon transport in amorphous materials is perhaps more complicated than previously thought. For instance, depending on the type of amorphous materials, thermal transport occurs via three types of vibrations: propagons, diffusons, and locons, corresponding to the propagating, diffusion, and localized modes, respectively. The relative contribution of each of these modes dictates the thermal conductivity of the material, including its magnitude and its dependence on sample size and temperature. In this article, we will review the fundamental principles and recent development regarding thermal transport in amorphous semiconductors.

  3. Amorphous boron nitride at high pressure

    NASA Astrophysics Data System (ADS)

    Durandurdu, Murat

    2016-06-01

    The pressure-induced phase transformation in hexagonal boron nitrite and amorphous boron nitrite is studied using ab initio molecular dynamics simulations. The hexagonal-to-wurtzite phase transformation is successfully reproduced in the simulation with a transformation mechanism similar to one suggested in experiment. Amorphous boron nitrite, on the other hand, gradually transforms to a high-density amorphous phase with the application of pressure. This phase transformation is irreversible because a densified amorphous state having both sp3 and sp2 bonds is recovered upon pressure release. The high-density amorphous state mainly consists of sp3 bonds and its local structure is quite similar to recently proposed intermediate boron nitrite phases, in particular tetragonal structure (P42/mnm), rather than the known the wurtzite or cubic boron nitrite due to the existence of four membered rings and edge sharing connectivity. On the basis of this finding we propose that amorphous boron nitrite might be best candidate as a starting structure to synthesize the intermediate phase(s) at high pressure and temperature (probably below 800 °C) conditions.

  4. Wear Resistant Amorphous and Nanocomposite Steel Coatings

    SciTech Connect

    Branagan, Daniel James; Swank, William David; Haggard, Delon C; Fincke, James Russell; Sordelet, D.

    2001-10-01

    In this article, amorphous and nanocomposite thermally deposited steel coatings have been formed by using both plasma and high-velocity oxy-fuel (HVOF) spraying techniques. This was accomplished by developing a specialized iron-based composition with a low critical cooling rate (?104 K/s) for metallic glass formation, processing the alloy by inert gas atomization to form micron-sized amorphous spherical powders, and then spraying the classified powder to form coatings. A primarily amorphous structure was formed in the as-sprayed coatings, independent of coating thickness. After a heat treatment above the crystallization temperature (568°C), the structure of the coatings self-assembled (i.e., devitrified) into a multiphase nanocomposite microstructure with 75 to 125 nm grains containing a distribution of 20 nm second-phase grain-boundary precipitates. Vickers microhardness testing revealed that the amorphous coatings were very hard (10.2 to 10.7 GPa), with further increases in hardness after devitrification (11.4 to 12.8 GPa). The wear characteristics of the amorphous and nanocomposite coatings were determined using both two-body pin-on-disk and three-body rubber wheel wet-slurry sand tests. The results indicate that the amorphous and nanocomposite steel coatings are candidates for a wide variety of wear-resistant applications.

  5. Neutron irradiation induced amorphization of silicon carbide

    NASA Astrophysics Data System (ADS)

    Snead, L. L.; Hay, J. C.

    1999-07-01

    This paper provides the properties of bulk stoichiometric silicon carbide which has been amorphized under neutron irradiation. Both high purity single crystal hcp and high purity, highly faulted (cubic) chemically vapor deposited (CVD) SiC were irradiated at approximately 60°C to a total fast neutron fluence of 2.6 × 10 25 n/m 2. Amorphization was seen in both materials as evidenced by TEM, electron diffraction and X-ray diffraction techniques. Physical properties for the amorphized single crystal material are reported including large changes in density (-10.8%), elastic modulus as measured using a nanoindentation technique (-45%), hardness as measured by nanoindentation (-45%), and standard Vickers hardness (-24%). Similar property changes are observed for the amorphized CVD SiC. Using measured thermal conductivity data for the CVD SiC sample, the critical temperature for amorphization at this neutron dose and flux, above which amorphization is not possible, is estimated to be greater than ˜125°C.

  6. Laboratory verification of the Active Particle-induced X-ray Spectrometer (APXS) on the Chang'e-3 mission

    NASA Astrophysics Data System (ADS)

    Zhang, Guang-Liang; Li, Chun-Lai; Fu, Xiao-Hui; Zhang, Li-Yan; Ban, Cao; Li, Han; Zou, Yong-Liao; Peng, Wen-Xi; Cui, Xing-Zhu; Zhang, Cheng-Mo; Wang, Huan-Yu

    2015-11-01

    In the Chang'e-3 mission, the Active Particle-induced X-ray Spectrometer (APXS) on the Yutu rover is used to analyze the chemical composition of lunar soil and rock samples. APXS data are only valid are only if the sensor head gets close to the target and integration time lasts long enough. Therefore, working distance and integration time are the dominant factors that affect APXS results. This study confirms the ability of APXS to detect elements and investigates the effects of distance and time on the measurements. We make use of a backup APXS instrument to determine the chemical composition of both powder and bulk samples under the conditions of different working distances and integration times. The results indicate that APXS can detect seven major elements, including Mg, Al, Si, K, Ca, Ti and Fe under the condition that the working distance is less than 30 mm and having an integration time of 30 min. The statistical deviation is smaller than 15%. This demonstrates the instrument's ability to detect major elements in the sample. Our measurements also indicate the increase of integration time could reduce the measurement error of peak area, which is useful for detecting the elements Mg, Al and Si. However, an increase in working distance can result in larger errors in measurement, which significantly affects the detection of the element Mg.

  7. Impact of vitamin E-blended UHMWPE wear particles on the osseous microenvironment in polyethylene particle-induced osteolysis

    PubMed Central

    Neuerburg, Carl; Loer, Theresa; Mittlmeier, Lena; Polan, Christina; Farkas, Zsuzsanna; Holdt, Lesca Miriam; Utzschneider, Sandra; Schwiesau, Jens; Grupp, Thomas M.; Böcker, Wolfgang; Aszodi, Attila; Wedemeyer, Christian; Kammerlander, Christian

    2016-01-01

    Aseptic loosening mediated by wear particle-induced osteolysis (PIO) remains the major cause of implant loosening in endoprosthetic surgery. The development of new vitamin E (α-tocopherol)-blended ultra-high molecular weight polyethylene (VE-UHMWPE) with increased oxidation resistance and improved mechanical properties has raised hopes. Furthermore, regenerative approaches may be opened, as vitamin E supplementation has shown neuroprotective characteristics mediated via calcitonin gene-related peptide (CGRP), which is known to affect bone remodeling in PIO. Therefore, the present study aimed to further clarify the impact of VE-UHMWPE wear particles on the osseous microenvironment and to identify the potential modulatory pathways involved. Using an established murine calvaria model, mice were subjected to sham operation (SHAM group), or treated with UHMWPE or VE-UHMWPE particles for different experimental durations (7, 14 and 28 days; n=6/group). Morphometric analysis by micro-computed tomography detected significant (p<0.01) and comparable signs of PIO in all particle-treated groups, whereas markers of inflammation [tumor necrosis factor (TNF)-α/tartrate resistant acid phosphatase (TRAP) staining] and bone remodeling [Dickkopf-related protein 1 (DKK-1)/osteoprotegerin (OPG)] were most affected in the early stages following surgery. Taking the present data into account, VE-UHMWPE appears to have a promising biocompatibility and increased ageing resistance. According to the α-CGRP serum levels and immunohistochemistry, the impact of vitamin E on neuropeptidergic signaling and its chance for regenerative approaches requires further investigation. PMID:27779642

  8. Alpha particles induce pan-nuclear phosphorylation of H2AX in primary human lymphocytes mediated through ATM.

    PubMed

    Horn, Simon; Brady, Darren; Prise, Kevin

    2015-10-01

    The use of high linear energy transfer radiations in the form of carbon ions in heavy ion beam lines or alpha particles in new radionuclide treatments has increased substantially over the past decade and will continue to do so due to the favourable dose distributions they can offer versus conventional therapies. Previously it has been shown that exposure to heavy ions induces pan-nuclear phosphorylation of several DNA repair proteins such as H2AX and ATM in vitro. Here we describe similar effects of alpha particles on ex vivo irradiated primary human peripheral blood lymphocytes. Following alpha particle irradiation pan-nuclear phosphorylation of H2AX and ATM, but not DNA-PK and 53BP1, was observed throughout the nucleus. Inhibition of ATM, but not DNA-PK, resulted in the loss of pan-nuclear phosphorylation of H2AX in alpha particle irradiated lymphocytes. Pan-nuclear gamma-H2AX signal was rapidly lost over 24h at a much greater rate than foci loss. Surprisingly, pan-nuclear gamma-H2AX intensity was not dependent on the number of alpha particle induced double strand breaks, rather the number of alpha particles which had traversed the cell nucleus. This distinct fluence dependent damage signature of particle radiation is important in both the fields of radioprotection and clinical oncology in determining radionuclide biological dosimetry and may be indicative of patient response to new radionuclide cancer therapies.

  9. Early applications of the R-matrix SAMMY code for charged-particle induced reactions and related covariances

    NASA Astrophysics Data System (ADS)

    Pigni, Marco T.; Gauld, Ian C.; Croft, Stephen

    2017-09-01

    The SAMMY code system is mainly used in nuclear data evaluations for incident neutrons in the resolved resonance region (RRR), however, built-in capabilities also allow the code to describe the resonance structure produced by other incident particles, including charged particles. (α,n) data provide fundamental information that underpins nuclear modeling and simulation software, such as ORIGEN and SOURCES4C, used for the analysis of neutron emission and definition of source emission processes. The goal of this work is to carry out evaluations of charged-particle-induced reaction cross sections in the RRR. The SAMMY code was recently used in this regard to generate a Reich-Moore parameterization of the available 17,18O(α,n) experimental cross sections in order to estimate the uncertainty in the neutron generation rates for uranium oxide fuel types. This paper provides a brief description of the SAMMY evaluation procedure for the treatment of 17,18O(α,n) reaction cross sections. The results are used to generate neutron source rates for a plutonium oxide matrix.

  10. Bound trace element content of bovine retinal disk membranes as determined by particle-induced x-ray emission.

    PubMed Central

    McCormick, L D

    1985-01-01

    Particle-induced x-ray emission (PIXE) was used to determine the trace element content of bovine retinal disk membranes. PIXE is a multielemental analytical technique capable of the simultaneous detection and quantization of all elements from sodium and above in atomic number. The multielemental capability of PIXE allows the analysis time per element to be very low if a number of elements are detected in each sample. In addition, the multielemental capability of PIXE can be used to determine elemental content with respect to an internal reference. Here the content of detected trace element per rhodopsin was determined without recourse to an external rhodopsin assay. This was accomplished by using the sulfur content of rhodopsin as an internal reference. Detected trace element contents per rhodopsin were 1.58 +/- 0.049 Ca, 0.081 +/- 0.024 Fe, 0.393 +/- 0.200 Cu, and 0.150 +/- 0.031 Zn. Upper limits were placed on the amount of manganese, molybdenum, and nickel per rhodopsin as 0.019, 0.019, and 0.006, respectively. Two proteins known to be present in disk membranes, retinol dehydrogenase and a large protein, approximately 238,000 mol wt, are considered as potential metallo-proteins. No correlation was observed between the content of any detected element and bleaching levels. PMID:3978208

  11. Amorphous calcium (ortho)phosphates.

    PubMed

    Dorozhkin, Sergey V

    2010-12-01

    Amorphous calcium phosphates (ACPs) represent a unique class of biomedically relevant calcium orthophosphate salts, having variable chemical but essentially identical glass-like physical properties, in which there is neither translational nor orientational long-range ordering of the atomic positions. Normally, ACPs are the first solid phases, precipitated after a rapid mixing of aqueous solutions containing ions of Ca(2+) and PO₄³⁻; however, other production techniques are known. Interestingly, ACPs prepared by wet-chemical techniques were found to have a relatively constant chemical composition over a relatively wide range of preparation conditions, which suggests the presence of a well-defined local structural unit, presumably with the structure of Ca₉(PO₄)₆ - so-called Posner cluster. However, the presence of similar clusters in ACPs produced by other techniques remains uncertain. All ACPs are thermodynamically unstable compounds and, unless stored in dry conditions or doped by stabilizers, spontaneously tend to transform to crystalline calcium orthophosphates, mainly to calcium apatites. This solution instability of ACPs and their easy transformation to crystalline phases are of a great biological relevance. Specifically, the initiating role ACPs play in matrix vesicle biomineralization raises the importance of ACPs from a mere laboratory curiosity to that of a key intermediate in skeletal calcification. In addition, due to significant chemical and structural similarities with calcified mammalian tissues, as well as excellent biocompatibility and bioresorbability, all types of ACPs are very promising candidates for the manufacture of artificial bone grafts. This review summarizes the current knowledge on the occurrence, preparation, composition, structure, major properties and biomedical applications of ACPs. To assist readers in looking for the specific details on ACPs, a great number of references have been collected and systematized. Copyright

  12. Electrons and phonons in amorphous semiconductors

    NASA Astrophysics Data System (ADS)

    Prasai, Kiran; Biswas, Parthapratim; Drabold, D. A.

    2016-07-01

    The coupling between lattice vibrations and electrons is one of the central concepts of condensed matter physics. The subject has been deeply studied for crystalline materials, but far less so for amorphous and glassy materials, which are among the most important for applications. In this paper, we explore the electron-lattice coupling using current tools of a first-principles computer simulation. We choose three materials to illustrate the phenomena: amorphous silicon (a-Si), amorphous selenium (a-Se) and amorphous gallium nitride (a-GaN). In each case, we show that there is a strong correlation between the localization of electron states and the magnitude of thermally induced fluctuations in energy eigenvalues obtained from the density-functional theory (i.e. Kohn-Sham eigenvalues). We provide a heuristic theory to explain these observations. The case of a-GaN, a topologically disordered partly ionic insulator, is distinctive compared to the covalent amorphous examples. Next, we explore the consequences of changing the charge state of a system as a proxy for tracking photo-induced structural changes in the materials. Where transport is concerned, we lend insight into the Meyer-Neldel compensation rule and discuss a thermally averaged Kubo-Greenwood formula as a means to estimate electrical conductivity and especially its temperature dependence. We close by showing how the optical gap of an amorphous semiconductor can be computationally engineered with the judicious use of Hellmann-Feynman forces (associated with a few defect states) using molecular dynamics simulations. These forces can be used to close or open an optical gap, and identify a structure with a prescribed gap. We use the approach with plane-wave density functional methods to identify a low-energy amorphous phase of silicon including several coordination defects, yet with a gap close to that of good quality a-Si models.

  13. Anthocyanin suppresses CoCrMo particle-induced osteolysis by inhibiting IKKα/β mediated NF-κB signaling in a mouse calvarial model.

    PubMed

    Li, Yamin; Li, Juehong; Li, Bin; Qin, Hui; Peng, Xiaochun; Zhao, Yaochao; Chen, Yunsu

    2017-05-01

    Wear particle-induced osteolysis and bone resorption have been identified as critical factors of implant failure and total joint revision, in which nuclear factor kappa B (NF-κB) signaling and chronic inflammation have been shown to play key roles. Although anthocyanin is known to have anti-inflammatory function via blocking NF-κB pathway, it is still unclear whether anthocyanin has a protective effect on particle-induced osteolysis. In the present study, we aimed to investigate the detailed effects and the underlying mechanism of anthocyanin on CoCrMo particle-induced osteolysis in a mouse calvavial model. One hundred and twelve male BALB/c mice were divided randomly into four groups: sham group (sham operation and injection with PBS), vehicle group (CoCrMo particle treatment and injection with PBS), low-dose anthocyanin group (CoCrMo particle treatment and injecting anthocyanin with 0.1mg/g/day), and high-dose anthocyanin group (CoCrMo particle treatment and injecting anthocyanin with 0.4mg/g/day). Mice were sacrificed after two weeks, harvesting the calvariae tissue for in depth analysis by micro-CT, histomorphometry, immunohistochemical and molecular biology analysis. As expected, anthocyanin markedly inhibited CoCrMo particle-induced inflammatory infiltration and decreased bone loss in vivo. Anthocyanin also reversed the increase in the ratio of receptor activator of nuclear factor kappa B ligand (RANKL)/osteoproteger (OPG) and suppressed osteoclast formation in CoCrMo particle-stimulated calvaria. Additionally, anthocyanin significantly reduced the expression and secretion of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) in the calvaria of CoCrMo-stimulated mice. Furthermore, we confirmed that anthocyanin attenuated osteolysis by blocking NF-κB pathway via inhibiting inhibitor of nuclear factor kappa-B kinase α/β (IKKα/β) phosphorylation. In conclusion, our study demonstrated that anthocyanin can protect against

  14. Iron-based amorphous alloys and methods of synthesizing iron-based amorphous alloys

    DOEpatents

    Saw, Cheng Kiong; Bauer, William A.; Choi, Jor-Shan; Day, Dan; Farmer, Joseph C.

    2016-05-03

    A method according to one embodiment includes combining an amorphous iron-based alloy and at least one metal selected from a group consisting of molybdenum, chromium, tungsten, boron, gadolinium, nickel phosphorous, yttrium, and alloys thereof to form a mixture, wherein the at least one metal is present in the mixture from about 5 atomic percent (at %) to about 55 at %; and ball milling the mixture at least until an amorphous alloy of the iron-based alloy and the at least one metal is formed. Several amorphous iron-based metal alloys are also presented, including corrosion-resistant amorphous iron-based metal alloys and radiation-shielding amorphous iron-based metal alloys.

  15. Amorphous Silicon Based Neutron Detector

    SciTech Connect

    Xu, Liwei

    2004-12-12

    Various large-scale neutron sources already build or to be constructed, are important for materials research and life science research. For all these neutron sources, neutron detectors are very important aspect. However, there is a lack of a high-performance and low-cost neutron beam monitor that provides time and temporal resolution. The objective of this SBIR Phase I research, collaboratively performed by Midwest Optoelectronics, LLC (MWOE), the University of Toledo (UT) and Oak Ridge National Laboratory (ORNL), is to demonstrate the feasibility for amorphous silicon based neutron beam monitors that are pixilated, reliable, durable, fully packaged, and fabricated with high yield using low-cost method. During the Phase I effort, work as been focused in the following areas: 1) Deposition of high quality, low-defect-density, low-stress a-Si films using very high frequency plasma enhanced chemical vapor deposition (VHF PECVD) at high deposition rate and with low device shunting; 2) Fabrication of Si/SiO2/metal/p/i/n/metal/n/i/p/metal/SiO2/ device for the detection of alpha particles which are daughter particles of neutrons through appropriate nuclear reactions; and 3) Testing of various devices fabricated for alpha and neutron detection; As the main results: · High quality, low-defect-density, low-stress a-Si films have been successfully deposited using VHF PECVD on various low-cost substrates; · Various single-junction and double junction detector devices have been fabricated; · The detector devices fabricated have been systematically tested and analyzed. · Some of the fabricated devices are found to successfully detect alpha particles. Further research is required to bring this Phase I work beyond the feasibility demonstration toward the final prototype devices. The success of this project will lead to a high-performance, low-cost, X-Y pixilated neutron beam monitor that could be used in all of the neutron facilities worldwide. In addition, the technologies

  16. Multifractal and mechanical analysis of amorphous solid dispersions.

    PubMed

    Adler, Camille; Teleki, Alexandra; Kuentz, Martin

    2017-05-15

    The formulation of lipophilic and hydrophobic compounds is a challenge for the pharmaceutical industry and it requires the development of complex formulations. Our first aim was to investigate hot-melt extrudate microstructures by means of multifractal analysis using scanning electron microscopy imaging. Since the microstructure can affect solid dosage form performance such as mechanical properties, a second objective was to study the influence of the type of adsorbent and of the presence of an amorphous compound on extrudate hardness. β-Carotene (BC) was chosen as poorly water-soluble model compound. Formulations containing a polymer, a lipid and two different silica based inorganic carriers were produced by hot-melt extrusion. Based on scanning electron microscopy/energy dispersive X-ray spectroscopy, the obtained images were analyzed using multifractal formalism. The breaking force of the strands was assessed by a three point bending test. Multifractal analysis and three point bending results showed that the nature of interparticle interactions in the inorganic carrier as well as the presence of amorphous BC had an influence on the microstructure and thus on the mechanical performance. The use of multifractal analysis and the study of the mechanical properties were complementary to better characterize and understand complex formulations obtained by hot-melt extrusion. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. On Coarse Projective Integration for Atomic Deposition in Amorphous Systems

    SciTech Connect

    Chuang, Claire Y.; Han, Sang M.; Zepeda-Ruiz, Luis A.; Sinno, Talid

    2015-10-02

    Direct molecular dynamics simulation of atomic deposition under realistic conditions is notoriously challenging because of the wide range of timescales that must be captured. Numerous simulation approaches have been proposed to address the problem, often requiring a compromise between model fidelity, algorithmic complexity and computational efficiency. Coarse projective integration, an example application of the ‘equation-free’ framework, offers an attractive balance between these constraints. Here, periodically applied, short atomistic simulations are employed to compute gradients of slowly-evolving coarse variables that are then used to numerically integrate differential equations over relatively large time intervals. A key obstacle to the application of this technique in realistic settings is the ‘lifting’ operation in which a valid atomistic configuration is recreated from knowledge of the coarse variables. Using Ge deposition on amorphous SiO2 substrates as an example application, we present a scheme for lifting realistic atomistic configurations comprised of collections of Ge islands on amorphous SiO2 using only a few measures of the island size distribution. In conclusion, the approach is shown to provide accurate initial configurations to restart molecular dynamics simulations at arbitrary points in time, enabling the application of coarse projective integration for this morphologically complex system.

  18. On Coarse Projective Integration for Atomic Deposition in Amorphous Systems

    DOE PAGES

    Chuang, Claire Y.; Han, Sang M.; Zepeda-Ruiz, Luis A.; ...

    2015-10-02

    Direct molecular dynamics simulation of atomic deposition under realistic conditions is notoriously challenging because of the wide range of timescales that must be captured. Numerous simulation approaches have been proposed to address the problem, often requiring a compromise between model fidelity, algorithmic complexity and computational efficiency. Coarse projective integration, an example application of the ‘equation-free’ framework, offers an attractive balance between these constraints. Here, periodically applied, short atomistic simulations are employed to compute gradients of slowly-evolving coarse variables that are then used to numerically integrate differential equations over relatively large time intervals. A key obstacle to the application of thismore » technique in realistic settings is the ‘lifting’ operation in which a valid atomistic configuration is recreated from knowledge of the coarse variables. Using Ge deposition on amorphous SiO2 substrates as an example application, we present a scheme for lifting realistic atomistic configurations comprised of collections of Ge islands on amorphous SiO2 using only a few measures of the island size distribution. In conclusion, the approach is shown to provide accurate initial configurations to restart molecular dynamics simulations at arbitrary points in time, enabling the application of coarse projective integration for this morphologically complex system.« less

  19. On coarse projective integration for atomic deposition in amorphous systems

    SciTech Connect

    Chuang, Claire Y. E-mail: meister@unm.edu Sinno, Talid; Han, Sang M. E-mail: meister@unm.edu; Zepeda-Ruiz, Luis A. E-mail: meister@unm.edu

    2015-10-07

    Direct molecular dynamics simulation of atomic deposition under realistic conditions is notoriously challenging because of the wide range of time scales that must be captured. Numerous simulation approaches have been proposed to address the problem, often requiring a compromise between model fidelity, algorithmic complexity, and computational efficiency. Coarse projective integration, an example application of the “equation-free” framework, offers an attractive balance between these constraints. Here, periodically applied, short atomistic simulations are employed to compute time derivatives of slowly evolving coarse variables that are then used to numerically integrate differential equations over relatively large time intervals. A key obstacle to the application of this technique in realistic settings is the “lifting” operation in which a valid atomistic configuration is recreated from knowledge of the coarse variables. Using Ge deposition on amorphous SiO{sub 2} substrates as an example application, we present a scheme for lifting realistic atomistic configurations comprised of collections of Ge islands on amorphous SiO{sub 2} using only a few measures of the island size distribution. The approach is shown to provide accurate initial configurations to restart molecular dynamics simulations at arbitrary points in time, enabling the application of coarse projective integration for this morphologically complex system.

  20. Novel Internal Friction of Amorphous Solids

    NASA Astrophysics Data System (ADS)

    Liu, Xiao

    1998-03-01

    Owing to the great sensitivity of the double-paddle oscillators, we have recently measured the low-temperature internal friction of amorphous silicon films (X. Liu, B. E. White, Jr., R. O. Pohl, E. Iwanizcko, K. M. Jones, A. H. Mahan, B. N. Nelson, R. S. Crandall, S. Veprek, Phys. Rev. Lett. 78), 4418 (1997). While e-beam evaporation, sputtering, or Si^+ ion implantation produce a-Si films with similar tunneling states as in all amorphous solids, hydrogenated a-Si films with 1 at.% H prepared by hot-wire chemical vapor deposition show no sign of any significant low energy excitations. This observation offers an exciting opportunity to study the structural origin of the low energy excitations common to amorphous solids. A possible explanation is that in the hydrogenated films the amorphous structure is closer to the fourfold coordinated continuous random network expected in amorphous Si, and thus the lattice is more constrained, resulting in the absence of tunneling states.

  1. SURVIVAL OF AMORPHOUS WATER ICE ON CENTAURS

    SciTech Connect

    Guilbert-Lepoutre, Aurelie

    2012-10-01

    Centaurs are believed to be Kuiper Belt objects in transition between Jupiter and Neptune before possibly becoming Jupiter family comets. Some indirect observational evidence is consistent with the presence of amorphous water ice in Centaurs. Some of them also display a cometary activity, probably triggered by the crystallization of the amorphous water ice, as suggested by Jewitt and this work. Indeed, we investigate the survival of amorphous water ice against crystallization, using a fully three-dimensional thermal evolution model. Simulations are performed for varying heliocentric distances and obliquities. They suggest that crystallization can be triggered as far as 16 AU, though amorphous ice can survive beyond 10 AU. The phase transition is an efficient source of outgassing up to 10-12 AU, which is broadly consistent with the observations of the active Centaurs. The most extreme case is 167P/CINEOS, which barely crystallizes in our simulations. However, amorphous ice can be preserved inside Centaurs in many heliocentric distance-obliquity combinations, below a {approx}5-10 m crystallized crust. We also find that outgassing due to crystallization cannot be sustained for a time longer than 10{sup 4}-10{sup 4} years, leading to the hypothesis that active Centaurs might have recently suffered from orbital changes. This could be supported by both observations (although limited) and dynamical studies.

  2. Amorphous silicon detectors in positron emission tomography

    SciTech Connect

    Conti, M. Lawrence Berkeley Lab., CA ); Perez-Mendez, V. )

    1989-12-01

    The physics of the detection process is studied and the performances of different Positron Emission Tomography (PET) system are evaluated by theoretical calculation and/or Monte Carlo Simulation (using the EGS code) in this paper, whose table of contents can be summarized as follows: a brief introduction to amorphous silicon detectors and some useful equation is presented; a Tantalum/Amorphous Silicon PET project is studied and the efficiency of the systems is studied by Monte Carlo Simulation; two similar CsI/Amorphous Silicon PET projects are presented and their efficiency and spatial resolution are studied by Monte Carlo Simulation, light yield and time characteristics of the scintillation light are discussed for different scintillators; some experimental result on light yield measurements are presented; a Xenon/Amorphous Silicon PET is presented, the physical mechanism of scintillation in Xenon is explained, a theoretical estimation of total light yield in Xenon and the resulting efficiency is discussed altogether with some consideration of the time resolution of the system; the amorphous silicon integrated electronics is presented, total noise and time resolution are evaluated in each of our applications; the merit parameters {epsilon}{sup 2}{tau}'s are evaluated and compared with other PET systems and conclusions are drawn; and a complete reference list for Xenon scintillation light physics and its applications is presented altogether with the listing of the developed simulation programs.

  3. Impact of vitamin E-blended UHMWPE wear particles on the osseous microenvironment in polyethylene particle-induced osteolysis.

    PubMed

    Neuerburg, Carl; Loer, Theresa; Mittlmeier, Lena; Polan, Christina; Farkas, Zsuzsanna; Holdt, Lesca Miriam; Utzschneider, Sandra; Schwiesau, Jens; Grupp, Thomas M; Böcker, Wolfgang; Aszodi, Attila; Wedemeyer, Christian; Kammerlander, Christian

    2016-12-01

    Aseptic loosening mediated by wear particle-induced osteolysis (PIO) remains the major cause of implant loosening in endoprosthetic surgery. The development of new vitamin E (α-tocopherol)-blended ultra-high molecular weight polyethylene (VE-UHMWPE) with increased oxidation resistance and improved mechanical properties has raised hopes. Furthermore, regenerative approaches may be opened, as vitamin E supplementation has shown neuroprotective characteristics mediated via calcitonin gene-related peptide (CGRP), which is known to affect bone remodeling in PIO. Therefore, the present study aimed to further clarify the impact of VE-UHMWPE wear particles on the osseous microenvironment and to identify the potential modulatory pathways involved. Using an established murine calvaria model, mice were subjected to sham operation (SHAM group), or treated with UHMWPE or VE-UHMWPE particles for different experimental durations (7, 14 and 28 days; n=6/group). Morphometric analysis by micro-computed tomography detected significant (p<0.01) and comparable signs of PIO in all particle-treated groups, whereas markers of inflammation [tumor necrosis factor (TNF)-α/tartrate resistant acid phosphatase (TRAP) staining] and bone remodeling [Dickkopf-related protein 1 (DKK-1)/osteoprotegerin (OPG)] were most affected in the early stages following surgery. Taking the present data into account, VE-UHMWPE appears to have a promising biocompatibility and increased ageing resistance. According to the α-CGRP serum levels and immunohistochemistry, the impact of vitamin E on neuropeptidergic signaling and its chance for regenerative approaches requires further investigation.

  4. Toxicity of Mineral Dusts and a Proposed Mechanism for the Pathogenesis of Particle-Induced Lung Diseases

    NASA Technical Reports Server (NTRS)

    Lam, C.-W.; Zeidler-Erdely, P.; Scully, R.R.; Meyers, V.; Wallace, W.; Hunter, R.; Renne, R.; McCluskey, R.; Castranova, V.; Barger, M.; hide

    2015-01-01

    Humans will set foot on the moon again. The lunar surface has been bombarded for 4 billion years by micrometeoroids and cosmic radiation, creating a layer of fine dust having a potentially reactive particle surface. To investigate the impact of surface reactivity (SR) on the toxicity of particles, and in particular, lunar dust (LD), we ground 2 Apollo 14 LD samples to increase their SR and compare their toxicity with those of unground LD, TiO2 and quartz. Intratracheally instilled at 0, 1, 2.5, or 7.5 mg/rat, all dusts caused dose-dependent increases in pulmonary lesions, and enhancement of biomarkers of toxicity assessed in bronchoalveolar lavage fluids (BALF). The toxicity of LD was greater than that of TiO2 but less than that of quartz. Three LDs differed 14-fold in SR but were equally toxic; quartz had the lowest SR but was most toxic. These results show no correlation between particle SR and toxicity. Often pulmonary toxicity of a dust can be attributed to oxidative stress (OS). We further observed dose-dependent and dustcytotoxicity- dependent increases in neutrophils. The oxidative content per BALF cell was also directly proportional to both the dose and cytotoxicity of the dusts. Because neutrophils are short-lived and release of oxidative contents after they die could initiate and promote a spectrum of lesions, we postulate a general mechanism for the pathogenesis of particle-induced diseases in the lung that involves chiefly neutrophils, the source of persistent endogenous OS. This mechanism explains why one dust (e.g., quartz or nanoparticles) is more toxic than another (e.g., micrometer-sized TiO2), why dust-induced lesions progress with time, and why lung cancer occurs in rats but not in mice and hamsters exposed to the same duration and concentration of dust.

  5. Maxwell rigidity and topological constraints in amorphous phase-change networks

    SciTech Connect

    Micoulaut, M.; Otjacques, C.; Raty, J.-Y.; Bichara, C.

    2011-12-12

    By analyzing first-principles molecular-dynamics simulations of different telluride amorphous networks, we develop a method for the enumeration of radial and angular topological constraints, and show that the phase diagram of the most popular system Ge-Sb-Te can be split into two compositional elastic phases: a tellurium rich flexible phase and a stressed rigid phase that contains most of the materials used in phase-change applications. This sound atomic scale insight should open new avenues for the understanding of phase-change materials and other complex amorphous materials from the viewpoint of rigidity.

  6. Only Amorphous Ethanethiol Exists in the Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Sivaraman, Bhalamurugan; Mason, Nigel; Chakrabarti, Sandip Kumar; Das, Ankan; Gorai, Prasanta; Rajan, Rabin; Pradeep, T.; Sundararajan, Pavithraa; Cheng, Bing-Ming

    2016-07-01

    In the ISM, it is now recognised that many molecular species are synthesised on the surface of dust grains which remain within the icy mantles on these grains until desorbed or sputtered (e.g., during star or planetary formation processes). Spitzer has revealed the presence of molecular ices in the dense clouds of the ISM but it is the advent of ALMA and then JWST that is expected to reveal the chemical complexity of such ices. Since the detection of methanol (CH_3OH) in Sgr A and Sgr B2 and hydrogen sulphide (H_2S) in Sgr B2, and other sources, it was long expected that a molecule containing thiol group could the synthesized in the complex chemical regions of the ISM. In 1979, first detection of methanethiol in Sgr B2 was reported. However, the first report on the detection of the higher order thiol, ethanethiol, has only been made recently in Orion KL, 30 years after the first observations of methanethiol, although the necessary precursors were detected earlier, ethylene in IRC +10216, ethanol in Sgr B2 and hydrogen sulfide. In the laboratory for experimental astrochemistry facility in PRL, thiol ices on cold dust grains are simulated and are probed by the FTIR for the first time. Ethanethiol ices were formed on zinc selenide substrate cooled to 10 K in an ultrahigh vacuum chamber. An infrared spectrum recorded after forming the ethanethiol ice at 10K revealed the ice formed to be amorphous in nature. Ices thus formed are then gradually warmed to higher temperatures with subsequent recording of infrared spectra. From the spectrum recorded at 180K, ethanethiol molecules from the ice phase were found to sublime. Until sublimation, which is typical indication for molecules turning from amorphous to crystalline phase, significant change in the infrared spectra, was not observed. Therefore we conclude that ethanethiol exists only in amorphous phase in the icy mantles of the cold dust grains. It is also the first known largest molecule to be present only in the

  7. Phase transitions in biogenic amorphous calcium carbonate

    PubMed Central

    Gong, Yutao U. T.; Killian, Christopher E.; Olson, Ian C.; Appathurai, Narayana P.; Amasino, Audra L.; Martin, Michael C.; Holt, Liam J.; Wilt, Fred H.; Gilbert, P. U. P. A.

    2012-01-01

    Crystalline biominerals do not resemble faceted crystals. Current explanations for this property involve formation via amorphous phases. Using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), here we examine forming spicules in embryos of Strongylocentrotus purpuratus sea urchins, and observe a sequence of three mineral phases: hydrated amorphous calcium carbonate (ACC·H2O) → dehydrated amorphous calcium carbonate (ACC) → calcite. Unexpectedly, we find ACC·H2O-rich nanoparticles that persist after the surrounding mineral has dehydrated and crystallized. Protein matrix components occluded within the mineral must inhibit ACC·H2O dehydration. We devised an in vitro, also using XANES-PEEM, assay to identify spicule proteins that may play a role in stabilizing various mineral phases, and found that the most abundant occluded matrix protein in the sea urchin spicules, SM50, stabilizes ACC·H2O in vitro. PMID:22492931

  8. IUE observations of amorphous hot galaxies

    NASA Technical Reports Server (NTRS)

    Lamb, S. A.; Hjellming, M. S.; Gallagher, J. S., III; Hunter, D. A.

    1985-01-01

    Blue amorphous galaxies are star-forming, irregularlike systems which lack the spatially distinct OB stellar groups that are characteristic of most late-type galaxies. In order to better understand the nature of star-formation processes in these unusual galaxies, short-wavelength IUE spectra of the amorphous galaxies NGC 1705 and NGC 1800 have been obtained. It is found that NGC 1705 contains a normal mix of OB stars, which is consistent with the nearly constant recent star-formation rate inferred from new optical data. NGC 1800 is likely to have similar properties, and blue galaxies with amorphous structures thus do not show evidence for anomalies in stellar populations. The UV spectra of these galaxies and a variety of other hot extragalactic stellar systems in fact have similar characteristics, which suggests OB stellar populations are often homogeneous in their properties.

  9. Investigation of superconducting interactions and amorphous semiconductors

    NASA Technical Reports Server (NTRS)

    Janocko, M. A.; Jones, C. K.; Gavaler, J. R.; Deis, D. W.; Ashkin, M.; Mathur, M. P.; Bauerle, J. E.

    1972-01-01

    Research papers on superconducting interactions and properties and on amorphous materials are presented. The search for new superconductors with improved properties was largely concentrated on the study of properties of thin films. An experimental investigation of interaction mechanisms revealed no new superconductivity mechanism. The properties of high transition temperature, type 2 materials prepared in thin film form were studied. A pulsed field solenoid capable of providing fields in excess of 300 k0e was developed. Preliminary X-ray measurements were made of V3Si to determine the behavior of cell constant deformation versus pressure up to 98 kilobars. The electrical properties of amorphous semiconducting materials and bulk and thin film devices, and of amorphous magnetic materials were investigated for developing radiation hard, inexpensive switches and memory elements.

  10. Amorphous metallic films in silicon metallization systems

    NASA Astrophysics Data System (ADS)

    So, F.; Kolawa, E.; Nicolet, M. A.

    1985-06-01

    Diffusion barrier research was focussed on lowering the chemical reactivity of amorphous thin films on silicon. An additional area of concern is the reaction with metal overlays such as aluminum, silver, and gold. Gold was included to allow for technology transfer to gallium arsenide PV cells. Amorphous tungsten nitride films have shown much promise. Stability to annealing temperatures of 700, 800, and 550 C were achieved for overlays of silver, gold, and aluminum, respectively. The lower results for aluminum were not surprising because there is an eutectic that can form at a lower temperature. It seems that titanium and zirconium will remove the nitrogen from a tungsten nitride amorphous film and render it unstable. Other variables of research interest were substrate bias and base pressure during sputtering.

  11. Nanocrystalline silicon/amorphous silicon dioxide superlattices

    SciTech Connect

    Fauchet, P.M.; Tsybeskov, L.; Zacharias, M. |; Hirschman, K. |

    1998-12-31

    Thin layers made of densely packed silicon nanocrystals sandwiched between amorphous silicon dioxide layers have been manufactured and characterized. An amorphous silicon/amorphous silicon dioxide superlattice is first grown by CVD or RF sputtering. The a-Si layers are recrystallized in a two-step procedure (nucleation + growth) for form layers of nearly identical nanocrystals whose diameter is given by the initial a-Si layer thickness. The recrystallization is monitored using a variety of techniques, including TEM, X-Ray, Raman, and luminescence spectroscopies. When the a-Si layer thickness decreases (from 25 nm to 2.5 nm) or the a-SiO{sub 2} layer thickness increases (from 1.5 nm to 6 nm), the recrystallization temperature increases dramatically compared to that of a single a-Si film. The removal of the a-Si tissue present between the nanocrystals, the passivation of the nanocrystals, and their doping are discussed.

  12. Amorphous metallic films in silicon metallization systems

    NASA Technical Reports Server (NTRS)

    So, F.; Kolawa, E.; Nicolet, M. A.

    1985-01-01

    Diffusion barrier research was focussed on lowering the chemical reactivity of amorphous thin films on silicon. An additional area of concern is the reaction with metal overlays such as aluminum, silver, and gold. Gold was included to allow for technology transfer to gallium arsenide PV cells. Amorphous tungsten nitride films have shown much promise. Stability to annealing temperatures of 700, 800, and 550 C were achieved for overlays of silver, gold, and aluminum, respectively. The lower results for aluminum were not surprising because there is an eutectic that can form at a lower temperature. It seems that titanium and zirconium will remove the nitrogen from a tungsten nitride amorphous film and render it unstable. Other variables of research interest were substrate bias and base pressure during sputtering.

  13. Amorphous/epitaxial superlattice for thermoelectric application

    NASA Astrophysics Data System (ADS)

    Ishida, Akihiro; Thao, Hoang Thi Xuan; Shibata, Mamoru; Nakashima, Seisuke; Tatsuoka, Hirokazu; Yamamoto, Hidenari; Kinoshita, Yohei; Ishikiriyama, Mamoru; Nakamura, Yoshiaki

    2016-08-01

    An amorphous/epitaxial superlattice system is proposed for application to thermoelectric devices, and the superlattice based on a PbGeTeS system was prepared by the alternate deposition of PbS and GeTe using a hot wall epitaxy technique. The structure was analyzed by high-resolution transmission electron microscopy (HRTEM) and X-ray analysis, and it was found that the superlattice consists of an epitaxial PbTe-based layer and a GeS-based amorphous layer by the reconstruction of the constituents. A reduction in thermal conductivity due to the amorphous/epitaxial system was confirmed by a 2ω method. Electrical and thermoelectric properties were measured for the samples.

  14. A single intraperitoneal injection of bovine fetuin-A attenuates bone resorption in a murine calvarial model of particle-induced osteolysis.

    PubMed

    Jablonski, Heidrun; Polan, Christina; Wedemeyer, Christian; Hilken, Gero; Schlepper, Rüdiger; Bachmann, Hagen Sjard; Grabellus, Florian; Dudda, Marcel; Jäger, Marcus; Kauther, Max Daniel

    2017-09-21

    Particle-induced osteolysis, which by definition is an aseptic inflammatory reaction to implant-derived wear debris eventually leading to local bone destruction, remains the major reason for long-term failure of orthopedic endoprostheses. Fetuin-A, a 66kDa glycoprotein with diverse functions, is found to be enriched in bone. Besides being an important inhibitor of ectopic calcification, it has been described to influence the production of mediators of inflammation. Furthermore, a regulatory role in bone metabolism has been assigned. In the present study, the influence of a single dose of bovine fetuin-A, intraperitoneally injected in mice subjected to particle-induced osteolysis of the calvaria, was analyzed. Twenty-eight male C57BL/6 mice, twelve weeks of age, were randomly divided into four groups. Groups 2 and 4 were subjected to ultra-high molecular weight polyethylene (UHMWPE) particles placed on their calvariae while groups 1 and 3 were sham-operated. Furthermore, groups 3 and 4 received a single intraperitoneal injection of 20mg bovine fetuin-A while groups 1 and 2 were treated with physiologic saline. After 14days calvarial bone was qualitatively and quantitatively assessed using microcomputed tomography (μCT) and histomorphometrical approaches. Application of fetuin-A led to a reduction of particle-induced osteolysis in terms of visible osteolytic lesions and eroded bone surface. The reduction of bone thickness and bone volume, as elicited by UHMWPE, was alleviated by fetuin-A. In conclusion, fetuin-A was found to exert an anti-resorptive effect on particle-induced osteolysis in-vivo. Thus, fetuin-A could play a potentially osteoprotective role in the treatment of bone metabolic disorders. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. The Phagocytosis and Toxicity of Amorphous Silica

    PubMed Central

    Costantini, Lindsey M.; Gilberti, Renée M.; Knecht, David A.

    2011-01-01

    Background Inhalation of crystalline silica is known to cause an inflammatory reaction and chronic exposure leads to lung fibrosis and can progress into the disease, silicosis. Cultured macrophages bind crystalline silica particles, phagocytose them, and rapidly undergo apoptotic and necrotic death. The mechanism by which particles are bound and internalized and the reason particles are toxic is unclear. Amorphous silica has been considered to be a less toxic form, but this view is controversial. We compared the uptake and toxicity of amorphous silica to crystalline silica. Methodology/Principal Findings Amorphous silica particles are phagocytosed by macrophage cells and a single internalized particle is capable of killing a cell. Fluorescent dextran is released from endo-lysosomes within two hours after silica treatment and Caspase-3 activation occurs within 4 hours. Interestingly, toxicity is specific to macrophage cell lines. Other cell types are resistant to silica particle toxicity even though they internalize the particles. The large and uniform size of the spherical, amorphous silica particles allowed us to monitor them during the uptake process. In mCherry-actin transfected macrophages, actin rings began to form 1-3 minutes after silica binding and the actin coat disassembled rapidly following particle internalization. Pre-loading cells with fluorescent dextran allowed us to visualize the fusion of phagosomes with endosomes during internalization. These markers provided two new ways to visualize and quantify particle internalization. At 37°C the rate of amorphous silica internalization was very rapid regardless of particle coating. However, at room temperature, opsonized silica is internalized much faster than non-opsonized silica. Conclusions/Significance Our results indicate that amorphous and crystalline silica are both phagocytosed and both toxic to mouse alveolar macrophage (MH-S) cells. The pathway leading to apoptosis appears to be similar in both

  16. Suppression of wear-particle-induced pro-inflammatory cytokine and chemokine production in macrophages via NF-κB decoy oligodeoxynucleotide: a preliminary report.

    PubMed

    Lin, Tzu-Hua; Yao, Zhenyu; Sato, Taishi; Keeney, Michael; Li, Chenguang; Pajarinen, Jukka; Yang, Fan; Egashira, Kensuke; Goodman, Stuart B

    2014-08-01

    Total joint replacement (TJR) is very cost-effective surgery for end-stage arthritis. One important goal is to decrease the revision rate, mainly because TJR has been extended to younger patients. Continuous production of ultra-high molecular weight polyethylene (UHMWPE) wear particles induces macrophage infiltration and chronic inflammation, which can lead to periprosthetic osteolysis. Targeting individual pro-inflammatory cytokines directly has not reversed the osteolytic process in clinical trials, owing to compensatory up-regulation of other pro-inflammatory factors. It is hypothesized that targeting the important transcription factor NF-κB could mitigate the inflammatory response to wear particles, potentially diminishing osteolysis. In the current study, NF-κB activity in mouse RAW 264.7 and human THP1 macrophage cell lines, as well as primary mouse and human macrophages, was suppressed via competitive binding with double strand decoy oligodeoxynucleotide (ODN) containing an NF-κB binding element. It was found that macrophage exposure to UHMWPE particles induced multiple pro-inflammatory cytokine and chemokine expression, including TNF-α, MCP1, MIP1α and others. Importantly, the decoy ODN significantly suppressed the induced cytokine and chemokine expression in both murine and human macrophages, and resulted in suppression of macrophage recruitment. The strategic use of decoy NF-κB ODN, delivered locally, could potentially diminish particle-induced periprosthetic osteolysis. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  17. Atomic Bond Deficiency Defects in Amorphous Metals

    NASA Astrophysics Data System (ADS)

    Zhu, Aiwu; Shiflet, Gary J.; Poon, S. Joseph

    2012-10-01

    Atomic bond deficiency (BD) is considered to be characteristic structural defects in amorphous metals. They are the necessary feature of local atomic configurations that facilitate various atomic transports under different driving forces. Compared with vacancies in crystalline solids, they are "small" in terms of their formation energies, volume costs, and elementary steps involved in atomic transport. This article reviews the authors' recent efforts made to analyze how various local configurations containing BD are related to amorphous metal's unique characteristics, such as glass transition, diffusion, shear flow, and structural relaxation.

  18. Neutron scattering studies of amorphous Invar alloys

    SciTech Connect

    Fernandez-Baca, J.A.

    1989-01-01

    This paper reviews recent inelastic neutron scattering experiments performed to study the spin dynamics of two amorphous Invar systems: Fe/sub 100-x/B/sub x/ and Fe/sub 90-x/Ni/sub x/Zr/sub 10/. As in crystalline Invar Fe/sub 65/Ni/sub 35/ and Fe/sub 3/Pt, the excitation of conventional long-wavelength spin waves in these amorphous systems cannot account for the relatively rapid change of their magnetization with temperature. These results are discussed in terms of additional low-lying excitations which apparently have a density of states similar to the spin waves.

  19. Thermal conductivity of sputtered amorphous Ge films

    SciTech Connect

    Zhan, Tianzhuo; Xu, Yibin; Goto, Masahiro; Tanaka, Yoshihisa; Kato, Ryozo; Sasaki, Michiko; Kagawa, Yutaka

    2014-02-15

    We measured the thermal conductivity of amorphous Ge films prepared by magnetron sputtering. The thermal conductivity was significantly higher than the value predicted by the minimum thermal conductivity model and increased with deposition temperature. We found that variations in sound velocity and Ge film density were not the main factors in the high thermal conductivity. Fast Fourier transform patterns of transmission electron micrographs revealed that short-range order in the Ge films was responsible for their high thermal conductivity. The results provide experimental evidences to understand the underlying nature of the variation of phonon mean free path in amorphous solids.

  20. Amorphous graphene: a realization of Zachariasen's glass.

    PubMed

    Kumar, Avishek; Wilson, Mark; Thorpe, M F

    2012-12-05

    Amorphous graphene is a realization of a two-dimensional Zachariasen glass as first proposed 80 years ago. Planar continuous random networks of this archetypal two-dimensional network are generated by two complementary simulation methods. In the first, a Monte Carlo bond switching algorithm is employed to systematically amorphize a crystalline graphene sheet. In the second, molecular dynamics simulations are utilized to quench from the high temperature liquid state. The two approaches lead to similar results as detailed here, through the pair distribution function and the associated diffraction pattern. Details of the structure, including ring statistics and angular distortions, are shown to be sensitive to preparation conditions, and await experimental confirmation.

  1. Radiation-induced amorphization of intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Lam, N. Q.; Sabochick, M. J.; Okamoto, P. R.

    1994-06-01

    In the present paper, important results of our recent computer simulation of radiation-induced amorphization in the ordered compounds CuTi and Cu4Ti3 are summarized. The energetic, structural, thermodynamic and mechanical responses of these intermetallics during chemical disordering, point-defect production and heating were simulated, using molecular dynamics and embedded-atom potentials. From the atomistic details obtained, the critical role of radiation-induced structural disorder in driving the crystalline-to-amorphous phase transformation is discussed.

  2. Amorphous Insulator Films With Controllable Properties

    NASA Technical Reports Server (NTRS)

    Alterovitz, Samuel A.; Warner, Joseph D.; Liu, David C.; Pouch, John J.

    1987-01-01

    In experiments described in report, amorphous hydrogenated carbon films grown at room temperature by low-frequency plasma deposition, using methane or butane gas. Films have unique array of useful properties; (a) adhere to wide variety of materials; (b) contain only carbon and hydrogen; (c) smooth and free of pinholes; (d) resistant to attack by moisture and chemicals; and (e) have high electric-breakdown strength and electrical resistivity. Two of optical properties and hardness of this film controlled by deposition conditions. Amorphous a-C:H and BN films used for hermetic sealing and protection of optical, electronic, magnetic, or delicate mechanical systems, and for semiconductor field dielectrics.

  3. Ion bombardment and disorder in amorphous silicon

    SciTech Connect

    Sidhu, L.S.; Gaspari, F.; Zukotynski, S.

    1997-07-01

    The effect of ion bombardment during growth on the structural and optical properties of amorphous silicon are presented. Two series of films were deposited under electrically grounded and positively biased substrate conditions. The biased samples displayed lower growth rates and increased hydrogen content relative to grounded counterparts. The film structure was examined using Raman spectroscopy. The transverse optic like phonon band position was used as a parameter to characterize network order. Biased samples displayed an increased order of the amorphous network relative to grounded samples. Furthermore, biased samples exhibited a larger optical gap. These results are correlated and attributed to reduced ion bombardment effects.

  4. Magnetic Phases in Amorphous Alloys.

    NASA Astrophysics Data System (ADS)

    Mazumdar, Prosenjit

    In magnetic amorphous alloy with competiting exchange interactions, there exists a multicritical point (MCP) in the temperature (T) vs. concentration (x) phase diagram (x(,c), (theta)(,c)). In the present work, the static (equilibrium) magnetic response near the MCP is thoroughly investigated using low, d.c. fields (B(,a) < 10 Oe) in two systems of alloys: (I) Fe(,x)Ni(,75-x)P(,16)B(,6)Al(,3) and (II) Fe(,x)Ni(,80-x)P(,14)B(,6). From the measurements of the reversible magnetization M(x, T, B(,a)), the following notable results are found: (1) The phase diagram exhibits a non-montonic FM-SG transition line (i.e. T(,f)'s) in both the systems. (2) There is a dramatic change in the magnetic response as x goes across x(,c). (3) The magnetization collapses as M(,P) (TURN) (x - x(,c))('0.3(+OR-)0.1) when x (--->) x(,c)('+). (4) The peak susceptibility diverges as (chi)(,P) (TURN) (x(,c) - x)('-1.5(+OR-)0.2) when x (--->) x(,c)('-). (5) The results (2), (3), and (4) are highly suggestive of a percolation transition in the magnetic network at the critical concentration for ferromagnetism (i.e. x(,c)). (6) Dramatic changes in the transition temperatures and a perceptible shift in x(,c) are observed when normal boron is replaced by enriched boron ((TURN)100% B('11)) in the series (I) samples. (7) The non-linear susceptibility ((chi)(,H)) exhibits the expected divergence at T(,g) with 'universal' exponents in concentrated spin glasses. (8) In the latter, a divergence in the linear susceptibility ((chi)(,o)) is observed for the first time. This is attributed to the close proximity of the ferromagnetic phase at x(,c). The study of the irreversible moment M(,i) (x, T, B(,a)) reveals the following: (9) Depending on the various methods of preparation, it is possible to generate states with different values of M(,i) at low T, all of which are stable (metastable) in time. This implies non -ergodic behavior. (10) For re-entrants (x > x(,c)), the amount of freezing achieved viz. M

  5. Origin of “memory glass” effect in pressure-amorphized rare-earth molybdate single crystals

    SciTech Connect

    Willinger, Elena; Sinitsyn, Vitaly; Khasanov, Salavat; Redkin, Boris; Shmurak, Semeon; Ponyatovsky, Eugeny

    2015-02-15

    The memory glass effect (MGE) describes the ability of some materials to recover the initial structure and crystallographic orientation after pressure-induced amorphization (PIA). In spite of numerous studies the nature and underlying mechanisms of this phenomenon are still not clear. Here we report investigations of MGE in β′-Eu{sub 2}(MoO{sub 4}){sub 3} single crystal samples subjected to high pressure amorphization. Using the XRD and TEM techniques we carried out detailed analysis of the structural state of high pressure treated single crystal samples as well as structural transformations due to subsequent annealing at atmospheric pressure. The structure of the sample has been found to be complex, mainly amorphous, however, the amorphous medium contains evenly distributed nanosize inclusions of a paracrystalline phase. The inclusions are highly correlated in orientation and act as “memory units” in the MGE. - Graphical abstract: Schematic representation of pressure-induced amorphization and “memory glass” effect in rare-earth molybdate single crystals. The XRD and TEM measurements have revealed the presence of the residual identically oriented paracrystalline nanodomains in the pressure-amorphized state. These domains preserve the information about initial structure and orientation of the sample. They act as memory units and crystalline seeds during transformation of the amorphous phase back to the starting single crystalline one. - Highlights: • Pressure-amorphized Eu{sub 2}(MoO4){sub 3} single crystals were studied ex-situ by XRD and TEM. • Tiny residual crystalline inclusions were found in amorphous matrix of sample. • The inclusions keep in memory the parent crystal structure and orientation. • The inclusions account for “memory glass” effect in rare-earth molibdates.

  6. Impact of polymers on the crystallization and phase transition kinetics of amorphous nifedipine during dissolution in aqueous media.

    PubMed

    Raina, Shweta A; Alonzo, David E; Zhang, Geoff G Z; Gao, Yi; Taylor, Lynne S

    2014-10-06

    The commercial and clinical success of amorphous solid dispersions (ASD) in overcoming the low bioavailability of poorly soluble molecules has generated momentum among pharmaceutical scientists to advance the fundamental understanding of these complex systems. A major limitation of these formulations stems from the propensity of amorphous solids to crystallize upon exposure to aqueous media. This study was specifically focused on developing analytical techniques to evaluate the impact of polymers on the crystallization behavior during dissolution, which is critical in designing effective amorphous formulations. In the study, the crystallization and polymorphic conversions of a model compound, nifedipine, were explored in the absence and presence of polyvinylpyrrolidone (PVP), hydroxypropylmethyl cellulose (HPMC), and HPMC-acetate succinate (HPMC-AS). A combination of analytical approaches including Raman spectroscopy, polarized light microscopy, and chemometric techniques such as multivariate curve resolution (MCR) were used to evaluate the kinetics of crystallization and polymorphic transitions as well as to identify the primary route of crystallization, i.e., whether crystallization took place in the dissolving solid matrix or from the supersaturated solutions generated during dissolution. Pure amorphous nifedipine, when exposed to aqueous media, was found to crystallize rapidly from the amorphous matrix, even when polymers were present in the dissolution medium. Matrix crystallization was avoided when amorphous solid dispersions were prepared, however, crystallization from the solution phase was rapid. MCR was found to be an excellent data processing technique to deconvolute the complex phase transition behavior of nifedipine.

  7. Amorphization and nanocrystallization of silcon under shock compression

    SciTech Connect

    Remington, B. A.; Wehrenberg, C. E.; Zhao, S.; Hahn, E. N.; Kad, B.; Bringa, E. M.; Meyers, M. A.

    2015-11-06

    High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon unveiled remarkable structural changes above a pressure threshold. Two distinct amorphous regions were identified: (a) a bulk amorphous layer close to the surface and (b) amorphous bands initially aligned with {111} slip planes. Further increase of the laser energy leads to the re-crystallization of amorphous silicon into nanocrystals with high concentration of nano-twins. This amorphization is produced by the combined effect of high magnitude hydrostatic and shear stresses under dynamic shock compression. Shock-induced defects play a very important role in the onset of amorphization. Calculations of the free energy changes with pressure and shear, using the Patel-Cohen methodology, are in agreement with the experimental results. Molecular dynamics simulation corroborates the amorphization, showing that it is initiated by the nucleation and propagation of partial dislocations. As a result, the nucleation of amorphization is analyzed qualitatively by classical nucleation theory.

  8. Inverted amorphous silicon solar cell utilizing cermet layers

    DOEpatents

    Hanak, Joseph J.

    1979-01-01

    An amorphous silicon solar cell incorporating a transparent high work function metal cermet incident to solar radiation and a thick film cermet contacting the amorphous silicon opposite to said incident surface.

  9. Metal electrode for amorphous silicon solar cells

    DOEpatents

    Williams, Richard

    1983-01-01

    An amorphous silicon solar cell having an N-type region wherein the contact to the N-type region is composed of a material having a work function of about 3.7 electron volts or less. Suitable materials include strontium, barium and magnesium and rare earth metals such as gadolinium and yttrium.

  10. Amorphous calcium carbonate particles form coral skeletons.

    PubMed

    Mass, Tali; Giuffre, Anthony J; Sun, Chang-Yu; Stifler, Cayla A; Frazier, Matthew J; Neder, Maayan; Tamura, Nobumichi; Stan, Camelia V; Marcus, Matthew A; Gilbert, Pupa U P A

    2017-08-28

    Do corals form their skeletons by precipitation from solution or by attachment of amorphous precursor particles as observed in other minerals and biominerals? The classical model assumes precipitation in contrast with observed "vital effects," that is, deviations from elemental and isotopic compositions at thermodynamic equilibrium. Here, we show direct spectromicroscopy evidence in Stylophora pistillata corals that two amorphous precursors exist, one hydrated and one anhydrous amorphous calcium carbonate (ACC); that these are formed in the tissue as 400-nm particles; and that they attach to the surface of coral skeletons, remain amorphous for hours, and finally, crystallize into aragonite (CaCO3). We show in both coral and synthetic aragonite spherulites that crystal growth by attachment of ACC particles is more than 100 times faster than ion-by-ion growth from solution. Fast growth provides a distinct physiological advantage to corals in the rigors of the reef, a crowded and fiercely competitive ecosystem. Corals are affected by warming-induced bleaching and postmortem dissolution, but the finding here that ACC particles are formed inside tissue may make coral skeleton formation less susceptible to ocean acidification than previously assumed. If this is how other corals form their skeletons, perhaps this is how a few corals survived past CO2 increases, such as the Paleocene-Eocene Thermal Maximum that occurred 56 Mya.

  11. Plasma deposition of amorphous metal alloys

    DOEpatents

    Hays, A.K.

    1979-07-18

    Amorphous metal alloy coatings are plasma-deposited by dissociation of vapors of organometallic compounds and metalloid hydrides in the presence of a reducing gas, using a glow discharge. Tetracarbonylnickel, phosphine, and hydrogen constitute a typical reaction mixture of the invention, yielding a NiPC alloy.

  12. Structural modeling of amorphous conducting carbon film

    NASA Astrophysics Data System (ADS)

    Bhattacharyya, Somnath; Pati, Swapan K.; Subramanyam, S. V.

    1998-04-01

    Amorphous conducting carbon films are prepared using plasma assisted polymerization process. SEM and TEM shows random aggregate of globular clusters of micron size inside the samples. Electrical measurements indicate a near metallic nature. A tendency of saturation of resistivity at low temperature is observed. From spectroscopic analysis we find some unusual features. Based on these observations a structural model of this carbon is proposed.

  13. Low temperature internal friction of amorphous silicon

    NASA Astrophysics Data System (ADS)

    Liu, Xiao; Metcalf, Thomas; Jernigan, Glenn; Jugdersuren, Battogtokh; Kearney, Brian; Culberston, James

    The ubiquitous low-energy excitations, known as two-level tunnelling systems (TLS), are one of the universal phenomena of amorphous solids. These excitations dominate the acoustic, dielectric, and thermal properties of structurally disordered solids. Using the double-paddle oscillator internal friction measurement technique, we have shown that TLS can be made to almost completely disappear in e-beam deposited amorphous silicon (a-Si) as the growth temperature increased to 400°C. However, there is a mysterious broad maximum in internal friction at 2-3K, which we suspect to come from metallic contamination of our oscillators and is not related to a-Si. Our new result of a-Si, deposited in a different UHV system and on oscillators with a different type of metallic electrodes, confirms our suspicion. This lowers the upper bound of possible TLS content in a-Si, in terms of tunnelling strength, to below 10-6. Our results offer an encouraging opportunity to use growth temperature to improve the structure order of amorphous thin films and to develop high quality amorphous dielectrics for applications, such as in modern quantum devices. Work supported by the Office of Naval Research.

  14. High resolution amorphous silicon radiation detectors

    DOEpatents

    Street, R.A.; Kaplan, S.N.; Perez-Mendez, V.

    1992-05-26

    A radiation detector employing amorphous Si:H cells in an array with each detector cell having at least three contiguous layers (n-type, intrinsic, p-type), positioned between two electrodes to which a bias voltage is applied. An energy conversion layer atop the silicon cells intercepts incident radiation and converts radiation energy to light energy of a wavelength to which the silicon cells are responsive. A read-out device, positioned proximate to each detector element in an array allows each such element to be interrogated independently to determine whether radiation has been detected in that cell. The energy conversion material may be a layer of luminescent material having a columnar structure. In one embodiment a column of luminescent material detects the passage therethrough of radiation to be detected and directs a light beam signal to an adjacent a-Si:H film so that detection may be confined to one or more such cells in the array. One or both electrodes may have a comb structure, and the teeth of each electrode comb may be interdigitated for capacitance reduction. The amorphous Si:H film may be replaced by an amorphous Si:Ge:H film in which up to 40 percent of the amorphous material is Ge. Two dimensional arrays may be used in X-ray imaging, CT scanning, crystallography, high energy physics beam tracking, nuclear medicine cameras and autoradiography. 18 figs.

  15. High resolution amorphous silicon radiation detectors

    DOEpatents

    Street, Robert A.; Kaplan, Selig N.; Perez-Mendez, Victor

    1992-01-01

    A radiation detector employing amorphous Si:H cells in an array with each detector cell having at least three contiguous layers (n type, intrinsic, p type), positioned between two electrodes to which a bias voltage is applied. An energy conversion layer atop the silicon cells intercepts incident radiation and converts radiation energy to light energy of a wavelength to which the silicon cells are responsive. A read-out device, positioned proximate to each detector element in an array allows each such element to be interrogated independently to determine whether radiation has been detected in that cell. The energy conversion material may be a layer of luminescent material having a columnar structure. In one embodiment a column of luminescent material detects the passage therethrough of radiation to be detected and directs a light beam signal to an adjacent a-Si:H film so that detection may be confined to one or more such cells in the array. One or both electrodes may have a comb structure, and the teeth of each electrode comb may be interdigitated for capacitance reduction. The amorphous Si:H film may be replaced by an amorphous Si:Ge:H film in which up to 40 percent of the amorphous material is Ge. Two dimensional arrays may be used in X-ray imaging, CT scanning, crystallography, high energy physics beam tracking, nuclear medicine cameras and autoradiography.

  16. TRANSIENT AMORPHOUS CALCIUM PHOSPHATE IN FORMING ENAMEL

    PubMed Central

    Beniash, Elia; Metzler, Rebecca A.; Lam, Raymond S.K.; Gilbert, P.U.P.A.

    2009-01-01

    Enamel, the hardest tissue in the body, begins as a three-dimensional network of nanometer size mineral particles, suspended in a protein gel. This mineral network serves as a template for mature enamel formation. To further understand the mechanisms of enamel formation we characterized the forming enamel mineral at an early secretory stage using x-ray absorption near-edge structure (XANES) spectromicroscopy, transmission electron microscopy (TEM), FTIR microspectroscopy and polarized light microscopy. We show that the newly formed enamel mineral is amorphous calcium phosphate (ACP), which eventually transforms into apatitic crystals. Interestingly, the size, shape and spatial organization of these amorphous mineral particles and older crystals are essentially the same, indicating that the mineral morphology and organization in enamel is determined prior to its crystallization. Mineralization via transient amorphous phases has been previously reported in chiton teeth, mollusk shells, echinoderm spicules and spines, and recent reports strongly suggest the presence transient amorphous mineral in forming vertebrate bones. The present finding of transient ACP in murine tooth enamel suggests that this strategy might be universal. PMID:19217943

  17. Amorphous calcium carbonate particles form coral skeletons

    PubMed Central

    Mass, Tali; Giuffre, Anthony J.; Sun, Chang-Yu; Stifler, Cayla A.; Frazier, Matthew J.; Neder, Maayan; Tamura, Nobumichi; Stan, Camelia V.; Marcus, Matthew A.

    2017-01-01

    Do corals form their skeletons by precipitation from solution or by attachment of amorphous precursor particles as observed in other minerals and biominerals? The classical model assumes precipitation in contrast with observed “vital effects,” that is, deviations from elemental and isotopic compositions at thermodynamic equilibrium. Here, we show direct spectromicroscopy evidence in Stylophora pistillata corals that two amorphous precursors exist, one hydrated and one anhydrous amorphous calcium carbonate (ACC); that these are formed in the tissue as 400-nm particles; and that they attach to the surface of coral skeletons, remain amorphous for hours, and finally, crystallize into aragonite (CaCO3). We show in both coral and synthetic aragonite spherulites that crystal growth by attachment of ACC particles is more than 100 times faster than ion-by-ion growth from solution. Fast growth provides a distinct physiological advantage to corals in the rigors of the reef, a crowded and fiercely competitive ecosystem. Corals are affected by warming-induced bleaching and postmortem dissolution, but the finding here that ACC particles are formed inside tissue may make coral skeleton formation less susceptible to ocean acidification than previously assumed. If this is how other corals form their skeletons, perhaps this is how a few corals survived past CO2 increases, such as the Paleocene–Eocene Thermal Maximum that occurred 56 Mya. PMID:28847944

  18. Plasma deposition of amorphous metal alloys

    DOEpatents

    Hays, Auda K.

    1986-01-01

    Amorphous metal alloy coatings are plasma-deposited by dissociation of vapors of organometallic compounds and metalloid hydrides in the presence of a reducing gas, using a glow discharge. Tetracarbonylnickel, phosphine, and hydrogen constitute a typical reaction mixture of the invention, yielding a NiPC alloy.

  19. Amorphous Molecular Organic Solids for Gas Adsorption

    SciTech Connect

    Tian, Jian; Thallapally, Praveen K.; Dalgarno, Scott J.; McGrail, B. Peter; Atwood, Jerry L.

    2009-07-06

    We show that molecular organic compounds with large accessible internal cavities, as part of their rigid molecular structure, display exceptional ability for gas storage and separation in the amorphous solid state. This finding suggests for the first time that long-range molecular order is not a prerequisite for organic molecules to be engineered as porous materials

  20. Amorphous calcium carbonate particles form coral skeletons

    NASA Astrophysics Data System (ADS)

    Mass, Tali; Giuffre, Anthony J.; Sun, Chang-Yu; Stifler, Cayla A.; Frazier, Matthew J.; Neder, Maayan; Tamura, Nobumichi; Stan, Camelia V.; Marcus, Matthew A.; Gilbert, Pupa U. P. A.

    2017-09-01

    Do corals form their skeletons by precipitation from solution or by attachment of amorphous precursor particles as observed in other minerals and biominerals? The classical model assumes precipitation in contrast with observed “vital effects,” that is, deviations from elemental and isotopic compositions at thermodynamic equilibrium. Here, we show direct spectromicroscopy evidence in Stylophora pistillata corals that two amorphous precursors exist, one hydrated and one anhydrous amorphous calcium carbonate (ACC); that these are formed in the tissue as 400-nm particles; and that they attach to the surface of coral skeletons, remain amorphous for hours, and finally, crystallize into aragonite (CaCO3). We show in both coral and synthetic aragonite spherulites that crystal growth by attachment of ACC particles is more than 100 times faster than ion-by-ion growth from solution. Fast growth provides a distinct physiological advantage to corals in the rigors of the reef, a crowded and fiercely competitive ecosystem. Corals are affected by warming-induced bleaching and postmortem dissolution, but the finding here that ACC particles are formed inside tissue may make coral skeleton formation less susceptible to ocean acidification than previously assumed. If this is how other corals form their skeletons, perhaps this is how a few corals survived past CO2 increases, such as the Paleocene–Eocene Thermal Maximum that occurred 56 Mya.

  1. Evaluation of amorphous solid dispersion properties using thermal analysis techniques.

    PubMed

    Baird, Jared A; Taylor, Lynne S

    2012-04-01

    Amorphous solid dispersions are an increasingly important formulation approach to improve the dissolution rate and apparent solubility of poorly water soluble compounds. Due to their complex physicochemical properties, there is a need for multi-faceted analytical methods to enable comprehensive characterization, and thermal techniques are widely employed for this purpose. Key parameters of interest that can influence product performance include the glass transition temperature (T(g)), molecular mobility of the drug, miscibility between the drug and excipients, and the rate and extent of drug crystallization. It is important to evaluate the type of information pertaining to the aforementioned properties that can be extracted from thermal analytical measurements, in addition to considering any inherent assumptions or limitations of the various analytical approaches. Although differential scanning calorimetry (DSC) is the most widely used thermal analytical technique applied to the characterization of amorphous solid dispersions, there are many established and emerging techniques which have been shown to provide useful information. Comprehensive characterization of fundamental material descriptors will ultimately lead to the formulation of more robust solid dispersion products. © 2011 Elsevier B.V. All rights reserved.

  2. Organization and mobility of water in amorphous and crystalline trehalose

    NASA Astrophysics Data System (ADS)

    Kilburn, Duncan; Townrow, Sam; Meunier, Vincent; Richardson, Robert; Alam, Ashraf; Ubbink, Job

    2006-08-01

    The disaccharide trehalose is accumulated by microorganisms, such as yeasts, and multicellular organisms, such as tardigrades, when conditions of extreme drought occur. In this way these organisms can withstand dehydration through the formation of an intracellular carbohydrate glass, which, with its high viscosity and hydrogen-bonding interactions, stabilizes and protects the integrity of complex biological structures and molecules. This property of trehalose can also be harnessed in the stabilization of liposomes, proteins and in the preservation of red blood cells, but the underlying mechanism of bioprotection is not yet fully understood. Here we use positron annihilation lifetime spectroscopy to probe the free volume of trehalose matrices; specifically, we develop a molecular picture of the organization and mobility of water in both amorphous and crystalline states. Whereas in amorphous matrices, water increases the average intermolecular hole size, in the crystalline dihydrate it is organized as a confined one-dimensional fluid in channels of fixed diameter that allow activated diffusion of water in and out of the crystallites. We present direct real-time evidence of water molecules unloading reversibly from these channels, thereby acting as both a sink and a source of water in low-moisture systems. We postulate that this behaviour may provide the overall stability required to keep organisms viable through dehydration conditions.

  3. Resolving 2D Amorphous Materials with Scanning Probe Microscopy

    NASA Astrophysics Data System (ADS)

    Burson, Kristen M.; Buechner, Christin; Lewandowski, Adrian; Heyde, Markus; Freund, Hans-Joachim

    Novel two-dimensional (2D) materials have garnered significant scientific interest due to their potential technological applications. Alongside the emphasis on crystalline materials, such as graphene and hexagonal BN, a new class of 2D amorphous materials must be pursued. For amorphous materials, a detailed understanding of the complex structure is necessary. Here we present a structural study of 2D bilayer silica on Ru(0001), an insulating material which is weakly coupled to the substrate. Atomic structure has been determined with a dual mode atomic force microscopy (AFM) and scanning tunneling microscopy (STM) sensor in ultra-high vacuum (UHV) at low temperatures, revealing a network of different ring sizes. Liquid AFM measurements with sub-nanometer resolution bridge the gap between clean UHV conditions and the environments that many material applications demand. Samples are grown and characterized in vacuum and subsequently transferred to the liquid AFM. Notably, the key structural features observed, namely nanoscale ring networks and larger holes to the substrate, show strong quantitative agreement between the liquid and UHV microscopy measurements. This provides direct evidence for the structural stability of these silica films for nanoelectronics and other applications. KMB acknowledges support from the Alexander von Humboldt Foundation.

  4. Sol gel-fluorination synthesis of amorphous magnesium fluoride

    NASA Astrophysics Data System (ADS)

    Krishna Murthy, J.; Groß, Udo; Rüdiger, Stephan; Kemnitz, Erhard; Winfield, John M.

    2006-03-01

    The sol-gel fluorination process is discussed for the reaction of magnesium alkoxides with HF in non-aqueous solvents to give X-ray amorphous nano-sized magnesium fluoride with high surface areas in the range of 150-350 m 2/g (HS-MgF 2). The H2 type hysteresis of nitrogen adsorption-desorption BET-isotherms is indicative for mesoporous solids. A highly distorted structure causes quite high Lewis acidity, shown by NH 3 temperature-programmed desorption (NH 3-TPD) and catalytic test reactions. XPS data of amorphous and conventionally crystalline MgF 2 are compared, both show octahedral coordination at the metal site. Thermal analysis, F-MAS NMR- and IR-spectroscopy give information on composition and structure of the precursor intermediate as well as of the final metal fluoride. The preparation of complex fluorides, M +MgF 3-, by the sol-gel route is reported. From the magnesium fluoride gel of the above process thin films for optical application are obtained by, e.g., spin coating.

  5. Amorphous silica-like carbon dioxide

    NASA Astrophysics Data System (ADS)

    Santoro, Mario; Gorelli, Federico A.; Bini, Roberto; Ruocco, Giancarlo; Scandolo, Sandro; Crichton, Wilson A.

    2006-06-01

    Among the group IV elements, only carbon forms stable double bonds with oxygen at ambient conditions. At variance with silica and germania, the non-molecular single-bonded crystalline form of carbon dioxide, phase V, only exists at high pressure. The amorphous forms of silica (a-SiO2) and germania (a-GeO2) are well known at ambient conditions; however, the amorphous, non-molecular form of CO2 has so far been described only as a result of first-principles simulations. Here we report the synthesis of an amorphous, silica-like form of carbon dioxide, a-CO2, which we call `a-carbonia'. The compression of the molecular phase III of CO2 between 40 and 48GPa at room temperature initiated the transformation to the non-molecular amorphous phase. Infrared spectra measured at temperatures up to 680K show the progressive formation of C-O single bonds and the simultaneous disappearance of all molecular signatures. Furthermore, state-of-the-art Raman and synchrotron X-ray diffraction measurements on temperature-quenched samples confirm the amorphous character of the material. Comparison with vibrational and diffraction data for a-SiO2 and a-GeO2, as well as with the structure factor calculated for the a-CO2 sample obtained by first-principles molecular dynamics, shows that a-CO2 is structurally homologous to the other group IV dioxide glasses. We therefore conclude that the class of archetypal network-forming disordered systems, including a-SiO2, a-GeO2 and water, must be extended to include a-CO2.

  6. Fabricating amorphous silicon solar cells by varying the temperature _of the substrate during deposition of the amorphous silicon layer

    DOEpatents

    Carlson, David E.

    1982-01-01

    An improved process for fabricating amorphous silicon solar cells in which the temperature of the substrate is varied during the deposition of the amorphous silicon layer is described. Solar cells manufactured in accordance with this process are shown to have increased efficiencies and fill factors when compared to solar cells manufactured with a constant substrate temperature during deposition of the amorphous silicon layer.

  7. Defect-induced solid state amorphization of molecular crystals

    NASA Astrophysics Data System (ADS)

    Lei, Lei; Carvajal, Teresa; Koslowski, Marisol

    2012-04-01

    We investigate the process of mechanically induced amorphization in small molecule organic crystals under extensive deformation. In this work, we develop a model that describes the amorphization of molecular crystals, in which the plastic response is calculated with a phase field dislocation dynamics theory in four materials: acetaminophen, sucrose, γ-indomethacin, and aspirin. The model is able to predict the fraction of amorphous material generated in single crystals for a given applied stress. Our results show that γ-indomethacin and sucrose demonstrate large volume fractions of amorphous material after sufficient plastic deformation, while smaller amorphous volume fractions are predicted in acetaminophen and aspirin, in agreement with experimental observation.

  8. Atomistic and infrared study of CO-water amorphous ice onto olivine dust grain

    NASA Astrophysics Data System (ADS)

    Escamilla-Roa, Elizabeth; Moreno, Fernando; López-Moreno, J. Juan; Sainz-Díaz, C. Ignacio

    2017-01-01

    This work is a study of CO and H2O molecules as adsorbates that interact on the surface of olivine dust grains. Olivine (forsterite) is present on the Earth, planetary dust, in the interstellar medium (ISM) and in particular in comets. The composition of amorphous ice is very important for the interpretation of processes that occur in the solar system and the ISM. Dust particles in ISM are composed of a heterogeneous mixture of amorphous or crystalline silicates (e.g. olivine) organic material, carbon, and other minor constituents. These dust grains are embedded in a matrix of ices, such as H2O, CO, CO2, NH3, and CH4. We consider that any amorphous ice will interact and grow faster on dust grain surfaces. In this work we explore the adsorption of CO-H2O amorphous ice onto several (100) forsterite surfaces (dipolar and non-dipolar), by using first principle calculations based on density functional theory (DFT). These models are applied to two possible situations: i) adsorption of CO molecules mixed into an amorphous ice matrix (gas mixture) and adsorbed directly onto the forsterite surface. This interaction has lower adsorption energy than polar molecules (H2O and NH3) adsorbed on this surface; ii) adsorption of CO when the surface has previously been covered by amorphous water ice (onion model). In this case the calculations show that adsorption energy is low, indicating that this interaction is weak and therefore the CO can be desorbed with a small increase of temperature. Vibration spectroscopy for the most stable complex was also studied and the frequencies were in good agreement with experimental frequency values.

  9. Major Elements Abundances in Chang'E-3 Landing Site from Active Particle-induced X-ray Spectrometer

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoping; Xie, Minggang; Zhu, Meng-Hua; Dong, Wudong; Tang, Zesheng; Xu, Aoao

    2015-04-01

    Chang'E-3, China's first Moon lander and rover mission, was launched at 17:30 on 1st December 2013 (UTC) and successfully landed on Moon surface at 13:11 on 14th December 2013 (UTC). About 8 hours later after the soft landing, the rover, named "Yutu' after a mythological rabbit that lives on the Moon as a pet of the Moon goddess, was successfully separated from the lander and started its adventure on the Moon. The success of this mission marks the first soft-landing on the Moon since 1976. The landing site is in northern Mare Imbrium (N44.12, W19.51), close to the boundary of two different geologic units and sits on 'young' Eratoshenian lava flows which spread several hundreds to thousands of kilometers. The mare basalts in the landing site are believed to be formed from the lava flows ~2.5 billion years ago, which are significantly younger than all of the returned lunar samples, dating from 3.1 to 3.8 billion years ago. This makes the landing site a very interesting place for exploring geochemical characteristics of the young lava flows and lunar evolution in a later stage. Active Particle-induced X-ray Spectrometer (APXS) is the only payload on the robotic arm of Yutu rover. It was designed to measure the intensities of characteristic fluorescent X-rays produced by interactions of lunar sample with incident X-rays. Major elements abundances of Mg, Al, Si, Ca, Ti, Fe on the lunar surface were expected to be detected after the exploration. On December 24th (UTC), 2013 and January 14th (UTC), 2014, APXS performed 4 successful measurements on lunar soils along Yutu's track. Characteristic peaks of Mg, Al, Si, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Sr and Zr could be clearly seen from the measured spectra. A global fit based on minimum chi-square method has been performed to disentangle different components in the measured spectra. These components include Kα and/or Kβ peaks of each element, escape peaks, exponential and shelf tail of major peaks and electronic noises, etc

  10. Amorphous-crystalline transition in thermoelectric NbO2

    NASA Astrophysics Data System (ADS)

    Music, Denis; Chen, Yen-Ting; Bliem, Pascal; Geyer, Richard W.

    2015-06-01

    Density functional theory was employed to design enhanced amorphous NbO2 thermoelectrics. The covalent-ionic nature of Nb-O bonding is identical in amorphous NbO2 and its crystalline counterpart. However, the Anderson localisation occurs in amorphous NbO2, which may affect the transport properties. We calculate a multifold increase in the absolute Seebeck coefficient for the amorphous state. These predictions were critically appraised by measuring the Seebeck coefficient of sputtered amorphous and crystalline NbO2 thin films with the identical short-range order. The first-order phase transition occurs at approximately 550 °C, but amorphous NbO2 possesses enhanced transport properties at all temperatures. Amorphous NbO2, reaching  -173 μV K-1, exhibits up to a 29% larger absolute Seebeck coefficient value, thereby validating the predictions.

  11. The Structure and Properties of Amorphous Indium Oxide

    PubMed Central

    2015-01-01

    A series of In2O3 thin films, ranging from X-ray diffraction amorphous to highly crystalline, were grown on amorphous silica substrates using pulsed laser deposition by varying the film growth temperature. The amorphous-to-crystalline transition and the structure of amorphous In2O3 were investigated by grazing angle X-ray diffraction (GIXRD), Hall transport measurement, high resolution transmission electron microscopy (HRTEM), electron diffraction, extended X-ray absorption fine structure (EXAFS), and ab initio molecular dynamics (MD) liquid-quench simulation. On the basis of excellent agreement between the EXAFS and MD results, a model of the amorphous oxide structure as a network of InOx polyhedra was constructed. Mechanisms for the transport properties observed in the crystalline, amorphous-to-crystalline, and amorphous deposition regions are presented, highlighting a unique structure–property relationship. PMID:25678743

  12. Atomic-scale disproportionation in amorphous silicon monoxide

    PubMed Central

    Hirata, Akihiko; Kohara, Shinji; Asada, Toshihiro; Arao, Masazumi; Yogi, Chihiro; Imai, Hideto; Tan, Yongwen; Fujita, Takeshi; Chen, Mingwei

    2016-01-01

    Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous structure characterized by angstrom-beam electron diffraction, supplemented by synchrotron X-ray scattering and computer simulations. In addition to the theoretically predicted amorphous silicon and silicon-dioxide clusters, suboxide-type tetrahedral coordinates are detected by angstrom-beam electron diffraction at silicon/silicon-dioxide interfaces, which provides compelling experimental evidence on the atomic-scale disproportionation of amorphous silicon monoxide. Eventually we develop a heterostructure model of the disproportionated silicon monoxide which well explains the distinctive structure and properties of the amorphous material. PMID:27172815

  13. Atomic-scale disproportionation in amorphous silicon monoxide.

    PubMed

    Hirata, Akihiko; Kohara, Shinji; Asada, Toshihiro; Arao, Masazumi; Yogi, Chihiro; Imai, Hideto; Tan, Yongwen; Fujita, Takeshi; Chen, Mingwei

    2016-05-13

    Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous structure characterized by angstrom-beam electron diffraction, supplemented by synchrotron X-ray scattering and computer simulations. In addition to the theoretically predicted amorphous silicon and silicon-dioxide clusters, suboxide-type tetrahedral coordinates are detected by angstrom-beam electron diffraction at silicon/silicon-dioxide interfaces, which provides compelling experimental evidence on the atomic-scale disproportionation of amorphous silicon monoxide. Eventually we develop a heterostructure model of the disproportionated silicon monoxide which well explains the distinctive structure and properties of the amorphous material.

  14. ER Stress Mediates TiAl6V4 Particle-Induced Peri-Implant Osteolysis by Promoting RANKL Expression in Fibroblasts

    PubMed Central

    Wang, Zhenheng; Liu, Naicheng; Shi, Tongguo; Zhou, Gang; Wang, Zhenzhen; Gan, Jingjing; Guo, Ting; Qian, Hongbo; Bao, Nirong; Zhao, Jianning

    2015-01-01

    Wear particle-induced osteolysis is a major cause of aseptic loosening, which is one of the most common reasons for total hip arthroplasty (THA) failure. Previous studies have shown that the synovial fibroblasts present in the periprosthetic membrane are important targets of wear debris during osteolysis. However, the interaction mechanisms between the wear debris and fibroblasts remain largely unknown. In the present study, we investigated the effect of ER (endoplasmic reticulum) stress induced by TiAl6V4 particles (TiPs) in human synovial fibroblasts and calvarial resorption animal models. The expression of ER stress markers, including IRE1-α, GRP78/Bip and CHOP, were determined by western blot in fibroblasts that had been treated with TiPs for various times and concentration. To address whether ER stress was involved in the expression of RANKL, the effects of ER stress blockers (including 4-PBA and TUDCA) on the expression of RANKL in TiPs-treated fibroblasts were examined by real-time PCR, western blot and ELISA. Osteoclastogenesis was assessed by tartrate resistant acid phosphatase (TRAP) staining. Our study demonstrated that ER stress markers were markedly upregulated in TiPs-treated fibroblasts. Blocking ER stress significantly reduced the TiPs-induced expression of RANKL both in vitro and in vivo. Moreover, the inhibition of ER stress ameliorated wear particle-induced osteolysis in animal models. Taken together, these results suggested that the expression of RANKL induced by TiPs was mediated by ER stress in fibroblasts. Therefore, down regulating the ER stress of fibroblasts represents a potential therapeutic approach for wear particle-induced periprosthetic osteolysis. PMID:26366858

  15. In vivo biological response to highly cross-linked and vitamin e-doped polyethylene--a particle-Induced osteolysis animal study.

    PubMed

    Huang, Chang-Hung; Lu, Yung-Chang; Chang, Ting-Kuo; Hsiao, I-Lin; Su, Yi-Ching; Yeh, Shu-Ting; Fang, Hsu-Wei; Huang, Chun-Hsiung

    2016-04-01

    Polyethylene particle-induced osteolysis is the primary limitation in the long-term success of total joint replacement with conventional ultra high molecular weight polyethylene (UHMWPE). Highly cross-linked polyethylene (HXLPE) and vitamin E-doped cross-linked polyethylene (VE-HXLPE) have been developed to increase the wear resistance of joint surfaces. However, very few studies have reported on the incidence of particle-induced osteolysis for these novel materials. The aim of this study was to use a particle-induced osteolysis animal model to compare the in vivo biological response to different polymer particles. Three commercially available polymers (UHMWPE, HXLPE, and VE-HXLPE) were compared. Osseous properties including the bone volume relative to the tissue volume (BV/TV), trabecular thickness (Tb. Th), and bone mineral density (BMD) were examined using micro computed tomography. Histological analysis was used to observe tissue inflammation in each group. This study demonstrated that the osseous properties and noticeable inflammatory reactions were obviously decreased in the HXLPE group. When compared with the sham group, a decrease of 12.7% was found in BV/TV, 9.6% in BMD and 8.3% in Tb.Th for the HXLPE group. The heightened inflammatory response in the HXLPE group could be due to its smaller size and greater amount of implanted particles. Vitamin E diffused in vivo may not affect the inflammatory and osteolytic responses in this model. The morphological size and total cumulative amount of implanted particles could be critical factors in determining the biological response.

  16. CHANG'E-3 Active Particle-induced X-ray Spectrometer: first detection near the landing site and preliminary analysis result

    NASA Astrophysics Data System (ADS)

    Peng, Wenxi; Cui, XingZhu; Wang, Huanyu; Guo, Dongya

    Active Particle-induced X-ray Spectrometer (APXS) onboard CHANG'E-3 Yutu rover was the first high energy resolution instrument of X-ray spectrometry sent to the lunar surface. The scientific objective of APXS is to investigate the elemental compositions along the route of the lunar rover on the Moon.Here, the first lunar soil detection near the landing site made by APXS is presented. The initial analysis indicate that the lunar regolith in this area is rich in both TiO2 and FeO, which is consistent with the remote sensing results.

  17. Improvement in limit of detection in particle induced X-ray emission by means of rise time and pulse shape discrimination

    NASA Astrophysics Data System (ADS)

    Papp, Tibor; Lakatos, Tamás; Nejedly, Zdenek; Campbell, John L.

    2002-04-01

    A digital signal processor, based upon high-rate sampling of the preamplifier output, and equipped with rise time and pulse shape discrimination, has been tested in three situations. This processor provided significant improvement of particle induced X-ray emission and X-ray fluorescence detection limits over the state of the art analog processors, depending on the energy and intensity distribution of the X-ray spectra. Additionally it had a superior performance when measurements were performed in an environment of large electronic noise and in large nuclear background environment. It has also improved the reduction of several artifacts in X-ray spectra.

  18. Disappearance and Creation of Constrained Amorphous Phase

    NASA Astrophysics Data System (ADS)

    Cebe, Peggy; Lu, Sharon X.

    1997-03-01

    We report observation of the disappearance and recreation of rigid, or constrained, amorphous phase by sequential thermal annealing. Tempera- ture modulated differential scanning calorimetry (MDSC) is used to study the glass transition and lower melting endotherm after annealing. Cold crystallization of poly(phenylene sulfide), PPS, at a temperature just above Tg creates an initial large fraction of rigid amorphous phase (RAP). Brief, rapid annealing to a higher temperature causes RAP almost to disappear completely. Subsequent reannealing at the original lower temperature restores RAP to its original value. At the same time that RAP is being removed, Tg decreases; when RAP is restored, Tg also returns to its initial value. The crystal fraction remains unaffected by the annealing sequence.

  19. Annealing behavior of high permeability amorphous alloys

    SciTech Connect

    Rabenberg, L.

    1980-06-01

    Effects of low temperature annealing on the magnetic properties of the amorphous alloy Co/sub 71/ /sub 4/Fe/sub 4/ /sub 6/Si/sub 9/ /sub 6/B/sub 14/ /sub 4/ were investigated. Annealing this alloy below 400/sup 0/C results in magnetic hardening; annealing above 400/sup 0/C but below the crystallization temperature results in magnetic softening. Above the crystallization temperature the alloy hardens drastically and irreversibly. Conventional and high resolution transmission electron microscopy were used to show that the magnetic property changes at low temperatures occur while the alloy is truly amorphous. By imaging the magnetic microstructures, Lorentz electron microscopy has been able to detect the presence of microscopic inhomogeneities in this alloy. The low temperature annealing behavior of this alloy has been explained in terms of atomic pair ordering in the presence of the internal molecular field. Lorentz electron microscopy has been used to confirm this explanation.

  20. Wear Resistant Amorphous and Nanocomposite Coatings

    SciTech Connect

    Racek, O

    2008-03-26

    Glass forming materials (critical cooling rate <10{sup 4}K.s{sup -1}) are promising for their high corrosion and wear resistance. During rapid cooling, the materials form an amorphous structure that transforms to nanocrystalline during a process of devitrification. High hardness (HV 1690) can be achieved through a controlled crystallization. Thermal spray process has been used to apply coatings, which preserves the amorphous/nanocomposite structure due to a high cooling rate of the feedstock particles during the impact on a substrate. Wear properties have been studied with respect to process conditions and feedstock material properties. Application specific properties such as sliding wear resistance have been correlated with laboratory tests based on instrumented indentation and scratch tests.

  1. Structural characterization of stable amorphous silicon films

    NASA Astrophysics Data System (ADS)

    Zhang, Shibin; Kong, Guanglin; Wang, Yongqian; Sheng, Shuran; Liao, Xianbo

    2002-05-01

    A kind of hydrogenated diphasic silicon films has been prepared by a new regime of plasma enhanced chemical vapor deposition (PECVD) in the region adjacent to the phase transition from amorphous to crystalline state. The photoelectronic and microstructural properties of the films have been investigated by the constant photocurrent method (CPM), Raman scattering and nuclear magnetic resonance (NMR). Our experimental results and corresponding analyses showed that the diphasic films, incorporated with a subtle boron compensation, could gain both the fine photosensitivity and high stability, provided the crystalline fraction ( f) was controlled in the range of 0< f<0.3. When compared with the conventional hydrogenated amorphous silicon (a-Si:H), the diphasic films are more ordered and robust in the microstructure, and have a less clustered phase in the Si-H bond configurations.

  2. Germanium detector passivated with hydrogenated amorphous germanium

    DOEpatents

    Hansen, William L.; Haller, Eugene E.

    1986-01-01

    Passivation of predominantly crystalline semiconductor devices (12) is provided for by a surface coating (21) of sputtered hydrogenated amorphous semiconductor material. Passivation of a radiation detector germanium diode, for example, is realized by sputtering a coating (21) of amorphous germanium onto the etched and quenched diode surface (11) in a low pressure atmosphere of hydrogen and argon. Unlike prior germanium diode semiconductor devices (12), which must be maintained in vacuum at cryogenic temperatures to avoid deterioration, a diode processed in the described manner may be stored in air at room temperature or otherwise exposed to a variety of environmental conditions. The coating (21) compensates for pre-existing undesirable surface states as well as protecting the semiconductor device (12) against future impregnation with impurities.

  3. Reversibility and criticality in amorphous solids

    DOE PAGES

    Regev, Ido; Weber, John; Reichhardt, Charles; ...

    2015-11-13

    The physical processes governing the onset of yield, where a material changes its shape permanently under external deformation, are not yet understood for amorphous solids that are intrinsically disordered. Here, using molecular dynamics simulations and mean-field theory, we show that at a critical strain amplitude the sizes of clusters of atoms undergoing cooperative rearrangements of displacements (avalanches) diverges. We compare this non-equilibrium critical behaviour to the prevailing concept of a ‘front depinning’ transition that has been used to describe steady-state avalanche behaviour in different materials. We explain why a depinning-like process can result in a transition from periodic to chaoticmore » behaviour and why chaotic motion is not possible in pinned systems. As a result, these findings suggest that, at least for highly jammed amorphous systems, the irreversibility transition may be a side effect of depinning that occurs in systems where the disorder is not quenched.« less

  4. Breakdown of elasticity in amorphous solids

    NASA Astrophysics Data System (ADS)

    Biroli, Giulio; Urbani, Pierfrancesco

    2016-12-01

    What characterizes a solid is the way that it responds to external stresses. Ordered solids, such as crystals, exhibit an elastic regime followed by a plastic regime, both understood microscopically in terms of lattice distortion and dislocations. For amorphous solids the situation is instead less clear, and the microscopic understanding of the response to deformation and stress is a very active research topic. Several studies have revealed that even in the elastic regime the response is very jerky at low temperature, resembling very much the response of disordered magnetic materials. Here we show that in a very large class of amorphous solids this behaviour emerges upon decreasing temperature, as a phase transition, where standard elastic behaviour breaks down. At the transition all nonlinear elastic moduli diverge and standard elasticity theory no longer holds. Below the transition, the response to deformation becomes history- and time-dependent.

  5. Reversibility and criticality in amorphous solids

    SciTech Connect

    Regev, Ido; Weber, John; Reichhardt, Charles; Dahmen, Karin A.; Lookman, Turab

    2015-11-13

    The physical processes governing the onset of yield, where a material changes its shape permanently under external deformation, are not yet understood for amorphous solids that are intrinsically disordered. Here, using molecular dynamics simulations and mean-field theory, we show that at a critical strain amplitude the sizes of clusters of atoms undergoing cooperative rearrangements of displacements (avalanches) diverges. We compare this non-equilibrium critical behaviour to the prevailing concept of a ‘front depinning’ transition that has been used to describe steady-state avalanche behaviour in different materials. We explain why a depinning-like process can result in a transition from periodic to chaotic behaviour and why chaotic motion is not possible in pinned systems. As a result, these findings suggest that, at least for highly jammed amorphous systems, the irreversibility transition may be a side effect of depinning that occurs in systems where the disorder is not quenched.

  6. Characterization of Amorphous Zinc Tin Oxide Semiconductors

    SciTech Connect

    Rajachidambaram, Jaana Saranya; Sanghavi, Shail P.; Nachimuthu, Ponnusamy; Shutthanandan, V.; Varga, Tamas; Flynn, Brendan T.; Thevuthasan, Suntharampillai; Herman, Gregory S.

    2012-06-12

    Amorphous zinc tin oxide (ZTO) was investigated to determine the effect of deposition and post annealing conditions on film structure, composition, surface contamination, and thin film transistor (TFT) device performance. X-ray diffraction results indicated that the ZTO films remain amorphous even after annealing to 600 °C. We found that the bulk Zn:Sn ratio of the sputter deposited films were slightly tin rich compared to the composition of the ceramic sputter target, and there was a significant depletion of zinc at the surface. X-ray photoelectron spectroscopy also indicated that residual surface contamination depended strongly on the sample post-annealing conditions where water, carbonate and hydroxyl species were absorbed to the surface. Electrical characterization of ZTO films, using TFT test structures, indicated that mobilities as high as 17 cm2/Vs could be obtained for depletion mode devices.

  7. Application of amorphous brush-plated

    NASA Astrophysics Data System (ADS)

    Zheng, M.; Zhu, Y.; Zheng, Z.

    1994-02-01

    The results obtained during industrial trials have shown that the service life of hot work dies can be increased by 33 to 180% using the brush plating technique to prepare amorphous coatings. The coatings possess a much higher hardness, lower friction coefficient at room and elevated temperatures, good scale resistance in addition to higher surface finish, compared to uncoated dies, and thus improve the tribological performance of the dies. In this work, a study of the crystallization process, its kinetics, and the hardness variations of the coatings has been made. According to the data obtained, it can be considered that the main reason for the success of amorphous brush-plated coatings is that, during the operation, crystallization and precipitation takes place instantaneously, which results in a strong secondary hardening effect, thus leading to an increase in the red hardness of the surface layers of dies, therefore ensuring higher thermal wear resistance of the dies.

  8. Study of an amorphous alloy core transformer

    NASA Astrophysics Data System (ADS)

    Nafalski, A.; Frost, D. C.

    1994-05-01

    Amorphous core transformers (ACT) have become a technological and commercial reality and there are an estimated 400,000 units installed worldwide [1]. Their applications reflect changes in buying practices, where the efficiency evaluation is an important factor in the purchasing decision for distribution transformers. Use of the total ownership cost (TOC) concept facilities the selection of a transformer on the basis of its performance. This concept is used in this paper to investigate the feasibility of applying a distribution ACT in Western Australian (WA). A 10 kVA ACT, evaluated by the TOC method, was compared with a traditional silicon iron core transformer of the same rating. The cost of amorphous metal (relative to alternative materials), the distribution load profile, and the values of capitalised loss costs are factors which affect the cost effectiveness of ACTs.

  9. Computer models for amorphous silicon hydrides

    NASA Astrophysics Data System (ADS)

    Mousseau, Normand; Lewis, Laurent J.

    1990-02-01

    A procedure for generating fully coordinated model structures appropriate to hydrogenated amorphous semiconductors is described. The hydrogen is incorporated into an amorphous matrix using a bond-switching process similar to that proposed by Wooten, Winer, and Weaire, which ensures that fourfold coordination is preserved. After each inclusion of hydrogen, the structure is relaxed using a finite-temperature Monte Carlo algorithm. The method is applied to a-Si:H at various hydrogen concentrations. The resulting model structures are found to be in excellent agreement with recent neutron-scattering measurements on a sample with 12 at. % H. Our prescription, which is essentially nonlocal, allows great flexibility and can easily be extended to related systems.

  10. New transformations between crystalline and amorphous ice

    NASA Technical Reports Server (NTRS)

    Hemley, R. J.; Chen, L. C.; Mao, H. K.

    1989-01-01

    High-pressure optical and spectroscopic techniques were used to obtain directly the ice I(h) - hda-ice transformation in a diamond-anvil cell, and the stability of the amorphous form is examined as functions of pressure and temperature. It is demonstrated that hda-ice transforms abruptly at 4 GPa and 77 K to a crystalline phase close in structure to orientationally disordered ice-VII and to a more highly ordered, ice-VIII-like structure at higher temperatures. This is the first time that an amorphous solid is observed to convert to a crystalline solid at low temperatures by compression alone. Phase transitions of this type may be relevant on icy planetary satellites, and there may also be implications for the high-pressure behavior of silica.

  11. Amorphous Magnetic Insulators for Microwave Device Applications

    DTIC Science & Technology

    1992-01-01

    magnetic characterization of amorphous BiFeO 3 films substituted with nonmagnetic perovskites, zinc ferrite, copper ferrite and calcium ferrite...G) Hu (Oe) AH (Oe) Tc (OC) (1-x) BiFeO 3 - x ABO3 AB = BaTi 200-1600 - -- 380-440 PbTi 100-450 - - 360-450 PbZr 400-3800 - - 440-490 (1-2x) BiFeO3 - x...II.B. BiFeO - ABO3 COMPOUNDS: Our studies show a ferrimagnetic character in the amorphous (a-) system (1-x) BiFeO3 - x ABO3 for x = 0.1 - 0.9. Here, AB0

  12. Phonon stop bands in amorphous superlattices

    NASA Astrophysics Data System (ADS)

    Koblinger, O.; Mebert, J.; Dittrich, E.; Döttinger, S.; Eisenmenger, W.; Santos, P. V.; Ley, L.

    1987-06-01

    In periodically layered media the phonon-dispersion relation shows energy ranges in which phonon propagation is not possible. The existence of such phonon stop bands in crystalline superlattices has been observed in work by V. Narayanamurti, H. L. Störmer, M. A. Chin, A. C. Gossard, and W. Wiegman [Phys. Rev. Lett. 43, 2012 (1979)]. In this Communication we report the observation of phonon stop bands in amorphous superlattices. The filter characteristic of these amorphous superlattices is much sharper than in the case of the crystalline superlattices studied earlier. The investigated superlattices have been prepared by alternating evaporation of Si and SiO2 layers as well as by plasma-enhanced chemical vapor deposition of a-Si:H/a-SiNx:H films in a glow-discharge reactor.

  13. Thermoluminescence characteristics of hydrogenated amorphous zirconia

    NASA Astrophysics Data System (ADS)

    Montalvo, T. R.; Tenorio, L. O.; Nieto, J. A.; Salgado, M. B.; Estrada, A. M. S.; Furetta, C.

    2005-05-01

    This paper reports the experimental results concerning the thermoluminescent (TL) characteristics of hydrogenated amorphous zirconium oxide (a-Zr:H) powder prepared by the sol-gel method. The advantages of this method are the homogeneity and the purity of the gels associated with a relatively low sintering temperature. Hydrogenated amorphous powder was characterized by thermal analysis and X-ray diffraction. The main TL characteristics investigated were the TL response as a function of the absorbed dose, the reproducibility of the TL readings and the fading. The undoped a-Zr:H powder presents a TL glow curve with two peaks centered at 150 and 260 degrees C, respectively, after beta irradiation. The TL response a-Zr:H as a function of the absorbed dose showed a linear behavior over a wide range. The results presented open the possibility to use this material as a good TL dosimeter.

  14. Synthesis of new amorphous metallic spin glasses

    DOEpatents

    Haushalter, Robert C.

    1986-01-01

    Amorphous metallic precipitates having the formula (M.sub.1).sub.a (M.sub.2).sub.b wherein M.sub.1 is at least one transition metal, M.sub.2 is at least one main group metal and the integers "a" and "b" provide stoichiometric balance; the precipitates having a degree of local order characteristic of chemical compounds from the precipitation process and useful electrical and mechanical properties.

  15. Synthesis of new amorphous metallic spin glasses

    DOEpatents

    Haushalter, Robert C.

    1988-01-01

    Amorphous metallic precipitates having the formula (M.sub.1).sub.a (M.sub.2).sub.b wherein M.sub.1 is at least one transition metal, M.sub.2 is at least one main group metal and the integers "a" and "b" provide stoichiometric balance; the precipitates having a degree of local order characteristic of chemical compounds from the precipitation process and useful electrical and mechanical properties.

  16. Synthesis of new amorphous metallic spin glasses

    DOEpatents

    Haushalter, R.C.

    1985-02-11

    Disclosed are: amorphous metallic precipitates having the formula (M/sub 1/)/sub a/(M/sub 2/)/sub b/ wherein M/sub 1/ is at least one transition metal, M/sub 2/ is at least one main group metal and the integers ''a'' and ''b'' provide stoichiometric balance; the precipitates having a degree of local order characteristic of chemical compounds from the precipitation process and useful electrical and mechanical properties.

  17. Ultrathin amorphous coatings on lunar dust grains.

    PubMed

    Bibring, J P; Duraud, J P; Durrieu, L; Jouret, C; Maurette, M; Meunier, R

    1972-02-18

    UItrathin amorphous coatings have been observed by high-voltage electron microscopy on micrometer-sized dust grains from the Apollo 11, Apollo 12, Apollo 14, and Luna 16 missions. Calibration experiments show that these coatings result from an "ancient" implantation of solar wind ions in the grains. This phenomenon has interdisciplinary applications concerning the past activity of the sun, the lunar albedo, the ancient lunar atmosphere and magnetic field, the carbon content of lunar soils, and lunar dynamic processes.

  18. Magnetic and magnetoelastic properties of amorphous ribbons

    SciTech Connect

    Chiriac, H.; Ciobotaru, I.; Mohorianu, S.

    1994-03-01

    A phenomenological model for the magnetic and magnetoelastic behavior of the field-annealed magnetostrictive ribbon is proposed. The basic hypothesis is that the magnetic domain coupling energy due to the inhomogeneity inherent to amorphous state is dependent on the reduced magnetization. The model takes into account the anisotropy energy, Zeeman energy, magnetoelastic energy and magnetic domain coupling energy. The magnetization, engineering magnetostriction and Young`s modulus are derived as continuous functions of the applied magnetic field and stress.

  19. Design Requirements for Amorphous Piezoelectric Polymers

    NASA Technical Reports Server (NTRS)

    Ounaies, Z.; Young, J. A.; Harrison, J. S.

    1999-01-01

    An overview of the piezoelectric activity in amorphous piezoelectric polymers is presented. The criteria required to render a polymer piezoelectric are discussed. Although piezoelectricity is a coupling between mechanical and electrical properties, most research has concentrated on the electrical properties of potentially piezoelectric polymers. In this work, we present comparative mechanical data as a function of temperature and offer a summary of polarization and electromechanical properties for each of the polymers considered.

  20. Multiple cell photoresponsive amorphous alloys and devices

    SciTech Connect

    Ovshinsky, S.R.; Adler, D.

    1990-01-02

    This patent describes an improved photoresponsive tandem multiple solar cell device. The device comprising: at least a first and second superimposed cell of various materials. The first cell being formed of a silicon alloy material. The second cell including an amorphous silicon alloy semiconductor cell body having an active photoresponsive region in which radiation can impinge to produce charge carriers, the amorphous cell body including at least one density of states reducing element. The element being fluorine. The amorphous cell body further including a band gap adjusting element therein at least in the photoresponsive region to enhance the radiation absorption thereof, the adjusting element being germanium: the second cell being a multi-layer body having deposited semiconductor layers of opposite (p and n) conductivity type; and the first cell being formed with the second cell in substantially direct Junction contact therebetween. The first and second cells designed to generate substantially matched currents from each cell from a light source directed through the first cell and into the second cell.

  1. Newtonian Flow in Bulk Amorphous Alloys

    SciTech Connect

    Wadsworth, J.; Nieh, T.G.

    2000-09-27

    Bulk amorphous alloys have many unique properties, e.g., superior strength and hardness, excellent corrosion resistance, reduced sliding friction and improved wear resistance, and easy formability in a viscous state. These properties, and particularly easy formability, are expected to lead to applications in the fields of near-net-shape fabrication of structural components. Whereas large tensile ductility has generally been observed in the supercooled liquid region in metallic glasses, the exact deformation mechanism, and in particular whether such alloys deform by Newtonian viscous flow, remains a controversial issue. In this paper, existing data are analyzed and an interpretation for the apparent controversy is offered. In addition, new results obtained from an amorphous alloy (composition: Zr-10Al-5TI-17.9Cu-14.6Ni, in at. %) are presented. Structural evolution during plastic deformation is particularly characterized. It is suggested that the appearance of non-Newtonian behavior is a result of the concurrent crystallization of the amorphous structure during deformation.

  2. Amorphous molybdenum silicon superconducting thin films

    SciTech Connect

    Bosworth, D. Sahonta, S.-L.; Barber, Z. H.; Hadfield, R. H.

    2015-08-15

    Amorphous superconductors have become attractive candidate materials for superconducting nanowire single-photon detectors due to their ease of growth, homogeneity and competitive superconducting properties. To date the majority of devices have been fabricated using W{sub x}Si{sub 1−x}, though other amorphous superconductors such as molybdenum silicide (Mo{sub x}Si{sub 1−x}) offer increased transition temperature. This study focuses on the properties of MoSi thin films grown by magnetron sputtering. We examine how the composition and growth conditions affect film properties. For 100 nm film thickness, we report that the superconducting transition temperature (Tc) reaches a maximum of 7.6 K at a composition of Mo{sub 83}Si{sub 17}. The transition temperature and amorphous character can be improved by cooling of the substrate during growth which inhibits formation of a crystalline phase. X-ray diffraction and transmission electron microscopy studies confirm the absence of long range order. We observe that for a range of 6 common substrates (silicon, thermally oxidized silicon, R- and C-plane sapphire, x-plane lithium niobate and quartz), there is no variation in superconducting transition temperature, making MoSi an excellent candidate material for SNSPDs.

  3. Flocculated amorphous nanoparticles for highly supersaturated solutions.

    PubMed

    Matteucci, Michal E; Paguio, Joseph C; Miller, Maria A; Williams Iii, Robert O; Johnston, Keith P

    2008-11-01

    To recover polymer-stabilized amorphous nanoparticles from aqueous dispersions efficiently by salt flocculation and to show that the particles redisperse and dissolve rapidly to produce highly supersaturated solutions. Nanoparticle dispersions of itraconazole stabilized by nonionic polymers were formed by antisolvent precipitation and immediately flocculated with sodium sulfate, filtered and dried. The size after redispersion in water, crystallinity, and morphology were compared with those for particles produced by spray drying and rapid freezing. Particle drug loading increased to approximately 90% after salt flocculation and removal of excess polymer with the filtrate. The formation of the flocs at constant particle volume fraction led to low fractal dimensions (open flocs), which facilitated redispersion in water to the original primary particle size of approximately 300 nm. Amorphous particles, which were preserved throughout the flocculation-filtration-drying process, dissolved to supersaturation levels of up to 14 in pH 6.8 media. In contrast, both spray dried and rapidly frozen nanoparticle dispersions crystallized and did not produce submicron particle dispersions upon addition to water, nor high supersaturation values. Salt flocculation produces large yields of high surface area amorphous nanoparticle powders that de-aggregate and dissolve rapidly upon redispersion in pH 6.8 media, for supersaturation levels up to 14.

  4. Shock induced crystallization of amorphous Nickel powders

    NASA Astrophysics Data System (ADS)

    Cherukara, Mathew; Strachan, Alejandro

    2015-06-01

    Recent experimental work has shown the efficacy of amorphous Ni/crystalline Al composites as energetic materials, with flame velocities twice that of a comparable crystalline Ni/crystalline Al system. Of further interest is the recrystallization mechanisms in the pure amorphous Ni powders, both thermally induced and mechanically induced. We present large-scale molecular dynamics simulations of shock-induced recrystallization in loosely packed amorphous Nickel powders. We study the time dependent nucleation and growth processes by holding the shocked samples at the induced pressures and temperatures for extended periods following the passage of the shock (up to 6 ns). We find that the nanostructure of the recrystallized Ni and time scales of recrystallization are dependent on the piston velocity. At low piston velocities, nucleation events are rare, leading to long incubation times and a relatively coarse nanostructure. At higher piston velocities, local variations in temperature due to jetting phenomena and void collapse, give rise to multiple nucleation events on time scales comparable to the passage of the shock wave, leading to the formation of a fine-grained nanostructure. Interestingly, we observe that the nucleation and growth process occurs in two steps, with the first nuclei crystallizing into the BCC structure, before evolving over time into the expected FCC structure. U.S. Defense Threat Reduction Agency, HDTRA1-10-1-0119 (Program Manager Suhithi Peiris).

  5. Phase transitions in biogenic amorphous calcium carbonate

    NASA Astrophysics Data System (ADS)

    Gong, Yutao

    Geological calcium carbonate exists in both crystalline phases and amorphous phases. Compared with crystalline calcium carbonate, such as calcite, aragonite and vaterite, the amorphous calcium carbonate (ACC) is unstable. Unlike geological calcium carbonate crystals, crystalline sea urchin spicules (99.9 wt % calcium carbonate and 0.1 wt % proteins) do not present facets. To explain this property, crystal formation via amorphous precursors was proposed in theory. And previous research reported experimental evidence of ACC on the surface of forming sea urchin spicules. By using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), we studied cross-sections of fresh sea urchin spicules at different stages (36h, 48h and 72h after fertilization) and observed the transition sequence of three mineral phases: hydrated ACC → dehydrated ACC → biogenic calcite. In addition, we unexpectedly found hydrated ACC nanoparticles that are surrounded by biogenic calcite. This observation indicates the dehydration from hydrated ACC to dehydrated ACC is inhibited, resulting in stabilization of hydrated ACC nanoparticles. We thought that the dehydration was inhibited by protein matrix components occluded within the biomineral, and we designed an in vitro assay to test the hypothesis. By utilizing XANES-PEEM, we found that SM50, the most abundant occluded matrix protein in sea urchin spicules, has the function to stabilize hydrated ACC in vitro.

  6. Interactions of hydrogen with amorphous hafnium oxide

    NASA Astrophysics Data System (ADS)

    Kaviani, Moloud; Afanas'ev, Valeri V.; Shluger, Alexander L.

    2017-02-01

    We used density functional theory (DFT) calculations to study the interaction of hydrogen with amorphous hafnia (a -HfO2 ) using a hybrid exchange-correlation functional. Injection of atomic hydrogen, its diffusion towards electrodes, and ionization can be seen as key processes underlying charge instability of high-permittivity amorphous hafnia layers in many applications. Hydrogen in many wide band gap crystalline oxides exhibits negative-U behavior (+1 and -1 charged states are thermodynamically more stable than the neutral state) . Our results show that in a -HfO2 hydrogen is also negative-U, with charged states being the most thermodynamically stable at all Fermi level positions. However, metastable atomic hydrogen can share an electron with intrinsic electron trapping precursor sites [Phys. Rev. B 94, 020103 (2016)., 10.1103/PhysRevB.94.020103] forming a [etr -+O -H ] center, which is lower in energy on average by about 0.2 eV. These electron trapping sites can affect both the dynamics and thermodynamics of the interaction of hydrogen with a -HfO2 and the electrical behavior of amorphous hafnia films in CMOS devices.

  7. Computer model of tetrahedral amorphous diamond

    NASA Astrophysics Data System (ADS)

    Djordjević, B. R.; Thorpe, M. F.; Wooten, F.

    1995-08-01

    We computer generate a model of amorphous diamond using the Wooten-Weaire method, with fourfold coordination everywhere. We investigate two models: one where four-membered rings are allowed and the other where the four-membered rings are forbidden; each model consisting of 4096 atoms. Starting from the perfect diamond crystalline structure, we first randomize the structure by introducing disorder through random bond switches at a sufficiently high temperature. Subsequently, the temperature is reduced in stages, and the topological and geometrical relaxation of the structure takes place using the Keating potential. After a long annealing process, a random network of comparatively low energy is obtained. We calculate the pair distribution function, mean bond angle, rms angular deviation, rms bond length, rms bond-length deviation, and ring statistics for the final relaxed structures. We minimize the total strain energy by adjusting the density of the sample. We compare our results with similar computer-generated models for amorphous silicon, and with experimental measurement of the structure factor for (predominantly tetrahedral) amorphous carbon.

  8. Formation of iron disilicide on amorphous silicon

    NASA Astrophysics Data System (ADS)

    Erlesand, U.; Östling, M.; Bodén, K.

    1991-11-01

    Thin films of iron disilicide, β-FeSi 2 were formed on both amorphous silicon and on crystalline silicon. The β-phase is reported to be semiconducting with a direct band-gap of about 0.85-0.89 eV. This phase is known to form via a nucleation-controlled growth process on crystalline silicon and as a consequence a rather rough silicon/silicide interface is usually formed. In order to improve the interface a bilayer structure of amorphous silicon and iron was sequentially deposited on Czochralski <111> silicon in an e-gun evaporation system. Secondary ion mass spectrometry profiling (SIMS) and scanning electron micrographs revealed an improvement of the interface sharpness. Rutherford backscattering spectrometry (RBS) and X-ray diffractiometry showed β-FeSi 2 formation already at 525°C. It was also observed that the silicide growth was diffusion-controlled, similar to what has been reported for example in the formation of NiSi 2 for the reaction of nickel on amorphous silicon. The kinetics of the FeSi 2 formation in the temperature range 525-625°C was studied by RBS and the activation energy was found to be 1.5 ± 0.1 eV.

  9. Crystalline-amorphous transition in silicate perovskites

    SciTech Connect

    Hemmati, M.; Chizmeshya, A. |; Wolf, G.H.; Poole, P.H.; Shao, J.; Angell, C.A.

    1995-06-01

    CaSiO{sub 3} and MgSiO{sub 3} perovskites are known to undergo solid-state crystal to amorphous transitions near ambient pressure when decompressed from their high-pressure stability fields. In order to elucidate the mechanistic aspects of this transition we have performed detailed molecular-dynamics simulations and lattice-dynamical calculations on model silicate perovskite systems using empirical rigid-ion pair potentials. In the simulations at low temperatures, the model perovskite systems transform under tension to a low-density glass composed of corner shared chains of tetrahedral silicon. The amorphization is initiated by a thermally activated step involving a soft polar optic mode in the perovskite phase at the Brillouin zone center. Progression of the system along this reaction coordinate triggers, in succession, multiple barrierless modes of instability ultimately producing a catastrophic decohesion of the lattice. An important intermediary along the reaction path is a crystalline phase where silicon is in a five-coordinate site and the alkaline-earth metal atom is in eightfold coordination. At the onset pressure, this transitory phase is itself dynamically unstable to a number of additional vibrational modes, the most relevant being those which result in transformation to a variety of tetrahedral chain silicate motifs. These results support the conjecture that stress-induced amorphization arises from the near simultaneous accessibility of multiple modes of instability in the highly metastable parent crystalline phase.

  10. Solid-state amorphization of rebamipide and investigation on solubility and stability of the amorphous form.

    PubMed

    Xiong, Xinnuo; Xu, Kailin; Li, Shanshan; Tang, Peixiao; Xiao, Ying; Li, Hui

    2017-02-01

    Solid-state amorphization of crystalline rebamipide (RBM) was realized by ball milling and spray drying. The amorphous content of samples milled for various time was quantified using X-ray powder diffraction. Crystalline RBM and three amorphous RBM obtained by milling and spray drying were characterized by morphological analysis, X-ray diffraction, thermal analysis and vibrational spectroscopy. The crystal structure of RBM was first determined by single-crystal X-ray diffraction. In addition, the solubility and dissolution rate of the RBM samples were investigated in different media. Results indicated that the solubility and the dissolution rates of spray-dried RBM-PVP in different media were highly improved compared with crystalline RBM. The physical stabilities of the three amorphous RBM were systematically investigated, and the stability orders under different storage temperatures and levels of relative humidity (RH) were both as follows: spray dried RBM < milled RBM < spray dried RBM-PVP. A direct glass-to-crystal transformation was induced under high RH, and the transformation rate rose with increasing RH. However, amorphous RBM could stay stable at RH levels lower than 57.6% (25 °C).

  11. Characterization of Amorphous and Co-Amorphous Simvastatin Formulations Prepared by Spray Drying.

    PubMed

    Craye, Goedele; Löbmann, Korbinian; Grohganz, Holger; Rades, Thomas; Laitinen, Riikka

    2015-12-03

    In this study, spray drying from aqueous solutions, using the surface-active agent sodium lauryl sulfate (SLS) as a solubilizer, was explored as a production method for co-amorphous simvastatin-lysine (SVS-LYS) at 1:1 molar mixtures, which previously have been observed to form a co-amorphous mixture upon ball milling. In addition, a spray-dried formulation of SVS without LYS was prepared. Energy-dispersive X-ray spectroscopy (EDS) revealed that SLS coated the SVS and SVS-LYS particles upon spray drying. X-ray powder diffraction (XRPD) and differential scanning calorimetry (DSC) showed that in the spray-dried formulations the remaining crystallinity originated from SLS only. The best dissolution properties and a "spring and parachute" effect were found for SVS spray-dried from a 5% SLS solution without LYS. Despite the presence of at least partially crystalline SLS in the mixtures, all the studied formulations were able to significantly extend the stability of amorphous SVS compared to previous co-amorphous formulations of SVS. The best stability (at least 12 months in dry conditions) was observed when SLS was spray-dried with SVS (and LYS). In conclusion, spray drying of SVS and LYS from aqueous surfactant solutions was able to produce formulations with improved physical stability for amorphous SVS.

  12. Characterizing Amorphous Silicates in Extraterrestrial Materials

    NASA Astrophysics Data System (ADS)

    Fu, X.; Wang, A.; Krawczynski, M. J.

    2015-12-01

    Amorphous silicates are common in extraterrestrial materials. They are seen in the matrix of carbonaceous chondrites as well as in planetary materials. Tagish Lake is one of the most primitive carbonaceous meteorites in which TEM and XRD analyses found evidence for poorly crystalline phyllosilicate-like species; Raman spectra revealed amorphous silicates with variable degree of polymerization and low crystallinity. On Mars, CheMin discovered amorphous phases in all analyzed samples, and poorly crystalline smectite in mudstone samples. These discoveries pose questions on the crystallinity of phyllosilicates found by remote sensing on Mars, which is directly relevant to aqueous alteration during geologic history of Mars. Our goal is to use spectroscopy to better characterize amorphous silicates. We use three approaches: (1) using silicate glasses synthesized with controlled chemistry to study the effects of silicate polymerization and (2) using phyllosilicates synthesized with controlled hydrothermal treatment to study the effect of crystallinity on vibrational spectroscopy, finally (3) to use the developed correlations in above two steps to study amorphous phases in meteorites, and those found in future missions to Mars. In the 1st step, silicate glasses were synthesized from pure oxides in a range of NBO/T ratios (from 0 to 4). Depending on the targeted NBO/T and composition of mixed oxides, temperatures for each experiment fell in a range from 1260 to 1520 °C, run for ~ 4 hrs. The melt was quenched in liquid N2 or water. Homogeneity of glass was checked under optical microscopy. Raman spectra were taken over 100 spots on small chips free of bubbles and crystals. We have observed that accompanying an increase of NBO/T, there is a strengthening and a position shift of the Raman peak near 1000 cm-1 (Si-Onon-bridging stretching mode), and the weakening of broad Raman peaks near 500 cm-1 (ring breathing mode) and 700cm-1 (Si-Obridging-Si mode). We are building the

  13. The Effect of Therapeutic Blockades of Dust Particles-Induced Ca2+ Signaling and Proinflammatory Cytokine IL-8 in Human Bronchial Epithelial Cells

    PubMed Central

    Yoon, Ju Hee; Jeong, Sung Hwan; Hong, Jeong Hee

    2015-01-01

    Bronchial epithelial cells are the first barrier of defense against respiratory pathogens. Dust particles as extracellular stimuli are associated with inflammatory reactions after inhalation. It has been reported that dust particles induce intracellular Ca2+ signal, which subsequently increases cytokines production such as interleukin- (IL-) 8. However, the study of therapeutic blockades of Ca2+ signaling induced by dust particles in human bronchial epithelial cells is poorly understood. We investigated how to modulate dust particles-induced Ca2+ signaling and proinflammatory cytokine IL-8 expression. Bronchial epithelial BEAS-2B cells were exposed to PM10 dust particles and subsequent mediated intracellular Ca2+ signaling and reactive oxygen species signal. Our results show that exposure to several inhibitors of Ca2+ pathway attenuated the PM10-induced Ca2+ response and subsequent IL-8 mRNA expression. PM10-mediated Ca2+ signal and IL-8 expression were attenuated by several pharmacological blockades such as antioxidants, IP3-PLC blockers, and TRPM2 inhibitors. Our results show that blockades of PLC or TRPM2 reduced both of PM10-mediated Ca2+ signal and IL-8 expression, suggesting that treatment with these blockades should be considered for potential therapeutic trials in pulmonary epithelium for inflammation caused by environmental events such as seasonal dust storm. PMID:26640326

  14. Exposure of Polyethylene Particles Induces Interferon-γ Expression in a Natural Killer T Lymphocyte and Dendritic Cell Co-Culture System in vitro: A Preliminary Study

    PubMed Central

    Lin, Tzu-hua; Sunny, Kao; Taishi, Sato; Pajarenin, Jukka; Zhang, Ruth; Loi, Florence; Goodman, Stuart B.; Yao, Zhenyu

    2014-01-01

    Two major issues in total joint arthroplasty are loosening of implants and osteolysis caused by wear particle-induced inflammation. Wear particles stimulate the release of pro-inflammatory cytokines, chemokines and other inflammatory mediators from macrophages and other cells. Although the biological response of macrophages to wear debris is well established, the role of other cell types such as natural killer T lymphocytes (NKT) and dendritic cells (DCs) is limited. Here we show that ultra-high molecular weight polyethylene (UHMWPE) particles stimulate NKT cells to secrete Interferon-γ (IFN-γ); co-culture with DCs further enhanced IFN-γ secretion. Furthermore, UHMWPE particles did not stimulate NKT cells to secrete IL-4, while the NKT cell natural ligand α-Galactosylceramide (α-GalCer) treatment in the co-culture system significantly enhanced both IFN-γ and IL-4 expression by NKT cells. Comparatively, NKT cells and/or DCs exposed to polymethylmethacrylate particles did not stimulate Interferon-γ or IL-4 expression. Mouse bone marrow derived macrophage polarization by lipopolysaccharide and conditioned medium from NKT cells and/or DCs exposed to UHMWPE particles increased TNF-α, but reduced arginase-1 expression in macrophages. The current findings indicate that UHMWPE particles stimulate NKT cells/DCs to produce pro-inflammatory cytokines; this pathway is a novel therapeutic target to mitigate wear particle induced peri-prosthetic osteolysis. PMID:24616165

  15. Application of HAADF STEM image analysis to structure determination in rotationally disordered and amorphous multilayered films

    NASA Astrophysics Data System (ADS)

    Mitchson, Gavin; Ditto, Jeffrey; Woods, Keenan N.; Westover, Richard; Page, Catherine J.; Johnson, David C.

    2016-08-01

    We report results from high angle annular dark field scanning transmission electron microscopy (HAADF STEM) image analysis of complex semi-crystalline and amorphous materials, and apply the insights gained from local structure information towards global structure determination. Variations in HAADF STEM intensities for a rotationally disordered heterostructure and an amorphous oxide film are statistically analyzed to extract information regarding the inhomogeneity of the films perpendicular to the substrate. By assuming chemical homogeneity in the film axis parallel to the substrate, the signal intensity variation parallel to the substrate is used to estimate the signal noise level, allowing evaluation of the significance of intensity differences in the substrate normal direction. The positions of HAADF STEM intensity peaks in the perpendicular direction, averaged from multiple images, provide a valuable initial model for a Rietveld refinement of the global c-axis structure of the heterostructure. For an amorphous multi-coat solution-cast oxide sample, the analysis reveals statistically significant variations in the HAADF STEM intensity profile perpendicular to the substrate. These variations indicate an inhomogeneous density profile, presumably related to the spin-casting of individual layers and have implications for understanding the chemical interactions that occur between layers when preparing multilayer amorphous oxide films from solution.

  16. Photoresponse dynamics in amorphous-LaAlO3/SrTiO3 interfaces

    PubMed Central

    Di Gennaro, Emiliano; Coscia, Ubaldo; Ambrosone, Giuseppina; Khare, Amit; Granozio, Fabio Miletto; di Uccio, Umberto Scotti

    2015-01-01

    The time-resolved photoconductance of amorphous and crystalline LaAlO3/SrTiO3 interfaces, both hosting an interfacial 2-dimensional electron gas, is investigated under irradiation by variable-wavelengths, visible or ultraviolet photons. Unlike bare SrTiO3 single crystals, showing relatively small photoconductance effects, both kinds of interfaces exhibit an intense and highly persistent photoconductance with extraordinarily long characteristic times. The temporal behaviour of the extra photoinduced conductance persisting after light irradiation shows a complex dependence on interface type (whether amorphous or crystalline), sample history and irradiation wavelength. The experimental results indicate that different mechanisms of photoexcitation are responsible for the photoconductance of crystalline and amorphous LaAlO3/SrTiO3 interfaces under visible light. We propose that the response of crystalline samples is mainly due to the promotion of electrons from the valence bands of both SrTiO3 and LaAlO3. This second channel is less relevant in amorphous LaAlO3/SrTiO3, where the higher density of point defects plays instead a major role. PMID:25670163

  17. Specific Adsorption of Clostridium stercorarium Xylanase to Amorphous Cellulose and Its Desorption by Cellobiose.

    PubMed

    Goro, T; Shuichi, K; Asako, T; Md Mainul, A; Tetsuya, K; Kazuo, S; Kunio, O

    1996-01-01

    Clostidium stercorarium xylanase A (XynA) composed of a family 11 catalytic domain of glycosyl hydrolases and family VI CBDs bound to amorphous cellulose, i.e., acid-swollen cellulose (ASC), but not highly crystalline cellulose, and it was released from the cellulose protein complex by wash with a cellobiose solution. The Ka and [PC]max values of ASC were 0.25 liter/μmol and 26μmol/g.

  18. Formation of amorphous silicon by light ion damage

    SciTech Connect

    Shih, Y.C.

    1985-12-01

    Amorphization by implantation of boron ions (which is the lightest element generally used in I.C. fabrication processes) has been systematically studied for various temperatures, various voltages and various dose rates. Based on theoretical considerations and experimental results, a new amorphization model for light and intermediate mass ion damage is proposed consisting of two stages. The role of interstitial type point defects or clusters in amorphization is emphasized. Due to the higher mobility of interstitials out-diffusion to the surface particularly during amorphization with low energy can be significant. From a review of the idealized amorphous structure, diinterstitial-divacancy pairs are suggested to be the embryos of amorphous zones formed during room temperature implantation. The stacking fault loops found in specimens implanted with boron at room temperature are considered to be the origin of secondary defects formed during annealing.

  19. Crystallization inhibition of an amorphous sucrose system using raffinose.

    PubMed

    Leinen, K M; Labuza, T P

    2006-02-01

    The shelf life of pure amorphous sucrose systems, such as cotton candy, can be very short. Previous studies have shown that amorphous sucrose systems held above the glass transition temperature will collapse and crystallize. One study, however, showed that adding a small percent of another type of sugar, such as trehalose, to sucrose can extend the shelf life of the amorphous system by slowing crystallization. This study explores the hypothesis that raffinose increases the stability of an amorphous sucrose system. Cotton candy at 5 wt% raffinose and 95 wt% sucrose was made and stored at room temperature and three different relative humidities (%RH) 11%RH, 33%RH, and 43%RH. XRD patterns, and glass transition temperatures were obtained to determine the stability as a function of %RH. The data collected showed that raffinose slows sucrose crystallization in a low moisture amorphous state above the glass transition temperature and therefore improves the stability of amorphous sucrose systems.

  20. Crystallization inhibition of an amorphous sucrose system using raffinose*

    PubMed Central

    Leinen, K.M.; Labuza, T.P.

    2006-01-01

    The shelf life of pure amorphous sucrose systems, such as cotton candy, can be very short. Previous studies have shown that amorphous sucrose systems held above the glass transition temperature will collapse and crystallize. One study, however, showed that adding a small percent of another type of sugar, such as trehalose, to sucrose can extend the shelf life of the amorphous system by slowing crystallization. This study explores the hypothesis that raffinose increases the stability of an amorphous sucrose system. Cotton candy at 5 wt% raffinose and 95 wt% sucrose was made and stored at room temperature and three different relative humidities (%RH) 11%RH, 33%RH, and 43%RH. XRD patterns, and glass transition temperatures were obtained to determine the stability as a function of %RH. The data collected showed that raffinose slows sucrose crystallization in a low moisture amorphous state above the glass transition temperature and therefore improves the stability of amorphous sucrose systems. PMID:16421962

  1. Molecular Dynamics Study of Crack Behavior in AN Amorphous Material

    NASA Astrophysics Data System (ADS)

    Ochoa, Oscar Romulo

    The fracture behavior of amorphous solids has received much attention due to the importance of these materials for a variety of applications in construction, transportation, including space vehicles, communications and computers, and under extreme environmental conditions, such as high temperatures, pressures and corrosive atmospheres. In this thesis, we strive to study the basic mechanisms of brittle fracture in amorphous solids and the atomic motions which affect brittle fracture and the onset of a mixed brittle/ductile behavior. The molecular dynamics technique was chosen to simulate a silica glass and study its behavior under different strain rates. This method was chosen because of its ability to probe the effect of atomic structure and atomic motions on the failure process, over a range of experimentally inaccessible strain rates. This investigation emphasizes the effects of vibrational relaxation on the material's strength. Experiments performed include strain rates in which no vibrational equilibration by the atoms is allowed and others in which the strain rates are low enough so that local rearrangements through vibrational motions are permitted but no other relaxation processes occur. Cases studied include flawless samples and samples with empty cracks and liquid filled cracks. It is found that molecular dynamics provides us with a unique method to determine the intrinsic strength of materials. In this study it is found unexpectedly that at low strain rates stresses in the samples are greatly relieved through vibrational motion which cause bond stretching and SiO(,4) tetrahedral rotation, thus, a material's strength is reduced by almost 60% through these vibrational rearrangements. The presence of voids in a material reduces their strength proportionally to the size of the cracks. A Lennard-Jones liquid added inside the voids proved to have negligible effect on the samples' strength, and it is postulated that a study of the phenomenon of slow crack growth

  2. Dynamics of radiation-induced amorphization in intermetallic compounds

    SciTech Connect

    Lam, N.Q.; Okamoto, P.R. ); Devanathan, R. Northwestern Univ., Evanston, IL . Dept. of Materials Science and Engineering); Meshii, M. . Dept. of Materials Science and Engineering)

    1992-06-01

    Recent progress in molecular-dynamics simulations of radiation-induced crystalline-to-amorphous transition in intermetallic compounds and the relationship between amorphization and melting are discussed. By focusing on the mean-square static displacement, which provides a generic measure of energy stored in the lattice in the forms of chemical and topological disorder, a unified description of solid-state amorphization as a disorder-induced, isothermal melting process can be developed within the framework of a generalized Lindemann criterion.

  3. CORROSION RESISTANCE OF STRUCTURAL AMORPHOUS METAL

    SciTech Connect

    Lian, T; Day, S D; Farmer, J C

    2006-04-10

    Corrosion costs the Department of Defense billions of dollars every year, with an immense quantity of material in various structures undergoing corrosion. For example, in addition to fluid and seawater piping, ballast tanks, and propulsions systems, approximately 345 million square feet of structure aboard naval ships and crafts require costly corrosion control measures. The use of advanced corrosion-resistant materials to prevent the continuous degradation of this massive surface area would be extremely beneficial. The potential advantages of amorphous metals have been recognized for some time [Latanison 1985]. Iron-based corrosion-resistant, amorphous-metal coatings under development may prove important for maritime applications [Farmer et al. 2005]. Such materials could also be used to coat the entire outer surface of containers for the transportation and long-term storage of spent nuclear fuel, or to protect welds and heat affected zones, thereby preventing exposure to environments that might cause stress corrosion cracking [Farmer et al. 1991, 2000a, 2000b]. In the future, it may be possible to substitute such high-performance iron-based materials for more-expensive nickel-based alloys, thereby enabling cost savings in a wide variety of industrial applications. It should be noted that thermal-spray ceramic coatings have also been investigated for such applications [Haslam et al. 2005]. This report focuses on the corrosion resistance of a yttrium-containing amorphous metal, SAM1651. SAM1651 has a glass transition temperature of {approx}584 C, a recrystallization temperature of {approx}653 C, and a melting point of {approx}1121 C. The measured critical cooling rate for SAM1651 is {le} 80 K per second, respectively. The yttrium addition to SAM1651 enhances glass formation, as reported by Guo and Poon [2003]. The corrosion behavior of SAM1651 was compared with nickel-based Alloy 22 in electrochemical polarization measurements performed in several highly

  4. Switching in coplanar amorphous hydrogenated silicon devices

    NASA Astrophysics Data System (ADS)

    Avila, A.; Asomoza, R.

    2000-01-01

    Switching has been observed in a wide variety of materials and devices. Hydrogenated amorphous silicon has become one of the most important cases because of interest in neural network applications. Although there are many reports regarding this phenomenon, not all of the physical processes involved are still determined precisely. Therefore, some more experimental information is needed in order to achieve this task. Much of the behavior of the devices has been ascribed to the existence of a filamentary region which is produced after the first switching process, called forming. We observed this filamentary region in its full extension by producing forming in amorphous silicon devices with coplanar metallic contacts placed near each other (˜5 μm). The I-V characteristics, filament optical and atomic force microscopy images and chemical etching led us to correlate changes in resistance to metal inclusion into the amorphous film. There are two stages: the first is related to contact stabilization, the second to metal transport into the film bulk. Optical images show a permanent filamentary region after forming. AFM images of these filaments showed that they are formed essentially by material accumulation between the contacts. This material tends to get some atomic arrangement, becoming a polycrystalline solid. If the device was led to breakdown, such accumulation becomes either a hillock or a thin conducting channel connecting both contacts. In the case of a switching filament, the accumulation tends to be a chain of smaller hillocks along the conduction path. Metal from the contacts remains in the conduction path after forming and chemical etching indicated that it is placed near the path core. Before forming, a tunneling transport process can be ascribed to the non-ohmic behavior of the samples during the first stage of metallic inclusion.

  5. Total X-ray scattering, EXAFS, and Mössbauer spectroscopy analyses of amorphous ferric arsenate and amorphous ferric phosphate

    NASA Astrophysics Data System (ADS)

    Mikutta, Christian; Schröder, Christian; Marc Michel, F.

    2014-09-01

    Amorphous ferric arsenate (AFA, FeAsO4·xH2O) is an important As precipitate in a range of oxic As-rich environments, especially acidic sulfide-bearing mine wastes. Its structure has been proposed to consist of small polymers of single corner-sharing FeO6 octahedra (rFe-Fe ∼3.6 Å) to which arsenate is attached as a monodentate binuclear 2C complex ('chain model'). Here, we analyzed the structure of AFA and analogously prepared amorphous ferric phosphates (AFP, FePO4·xH2O) by a combination of high-energy total X-ray scattering, Fe K-edge X-ray absorption spectroscopy, and 57Fe Mössbauer spectroscopy. Pair distribution function (PDF) analysis of total X-ray scattering data revealed that the coherently scattering domain size of AFA and AFP is about 8 Å. The PDFs of AFA lacked Fe-Fe pair correlations at r ∼3.6 Å indicative of single corner-sharing FeO6 octahedra, which strongly supports a local scorodite (FeAsO4·2H2O) structure. Likewise, the PDFs and Fe K-edge extended X-ray absorption fine structure data of AFP were consistent with a local strengite (FePO4·2H2O) structure of isolated FeO6 octahedra being corner-linked to PO4 tetrahedra (rFe-P = 3.25(1) Å). Mössbauer spectroscopy analyses of AFA and AFP indicated a strong superparamagnetism. While AFA only showed a weak onset of magnetic hyperfine splitting at 5 K, magnetic ordering of AFP was completely absent at this temperature. Mössbauer spectroscopy may thus offer a convenient way to identify and quantify AFA and AFP in mineral mixtures containing poorly crystalline Fe(III)-oxyhydroxides. In summary, our results imply a close structural relationship between AFA and AFP and suggest that these amorphous materials serve as templates for the formation of scorodite and strengite (phosphosiderite) in strongly acidic low-temperature environments.

  6. Irreversible Enthalpic Relaxation of Rigid Amorphous Fraction in Isotactic Polystyrene

    NASA Astrophysics Data System (ADS)

    Xu, Hui; Cebe, Peggy

    2004-03-01

    The crystalline, rigid amorphous, and mobile amorphous fractions in isotactic polystyrene (iPS) were studied using: 1. quasi-isothermal temperature-modulated differential scanning calorimetry (TMDSC) (i.e., with step-wise increase of temperature), and 2. regular TMDSC (i.e., with constant rate of temperature increase). The crystal fraction was determined from wide angle X-ray scattering and endotherm analysis; mobile amorphous fraction was determined from heat capacity measurements at the glass transition. The validity of a three-phase model for iPS (comprising crystals, mobile and rigid amorphous fractions) is confirmed by heat capacity measurements made during quasi-isothermal cold crystallization. At the same time, we prove the rigid amorphous fraction to be established at the crystallization temperature and not during subsequent cooling. The rigid amorphous fraction is thus stable below the crystallization temperature Tc, and relaxes at a temperature Ta, between Tc and the melting point of the lowest melting crystals. Upon relaxing, the rigid amorphous fraction undergoes a phase transition to mobile amorphous fraction. For cold-crystallized iPS the relaxation of the rigid amorphous fraction is found to be an enthalpy involved, non-reversible relaxation occurring before the melting of the crystals.

  7. Delivery of poorly soluble compounds by amorphous solid dispersions.

    PubMed

    Lee, Thomas W Y; Boersen, Nathan A; Hui, H W; Chow, S F; Wan, K Y; Chow, Albert H L

    2014-01-01

    Solid state manipulation by amorphous solid dispersion has been the subject of intensive research for decades due to their excellent potential for dissolution and bioavailability enhancement. The present review aims to highlight the latest advancement in this area, with focus on the fundamentals, characterization, formulation development and manufacturing of amorphous solid dispersions as well as the new generation amorphization technologies. Additionally, specific applications of amorphous solid dispersion in the formulation of herbal drugs or bioactive natural products are reviewed to reflect the growing interest in this relatively neglected area.

  8. Recent advances in co-amorphous drug formulations.

    PubMed

    Dengale, Swapnil Jayant; Grohganz, Holger; Rades, Thomas; Löbmann, Korbinian

    2016-05-01

    Co-amorphous drug delivery systems have recently gained considerable interest in the pharmaceutical field because of their potential to improve oral bioavailability of poorly water-soluble drugs through drug dissolution enhancement as a result of the amorphous nature of the material. A co-amorphous system is characterized by the use of only low molecular weight components that are mixed into a homogeneous single-phase co-amorphous blend. The use of only low molecular weight co-formers makes this approach very attractive, as the amount of amorphous stabilizer can be significantly reduced compared with other amorphous stabilization techniques. Because of this, several research groups started to investigate the co-amorphous formulation approach, resulting in an increasing amount of scientific publications over the last few years. This study provides an overview of the co-amorphous field and its recent findings. In particular, we investigate co-amorphous formulations from the viewpoint of solid dispersions, describe their formation and mechanism of stabilization, study their impact on dissolution and in vivo performance and briefly outline the future potentials.

  9. Magnetron-Sputtered Amorphous Metallic Coatings

    NASA Technical Reports Server (NTRS)

    Thakoor, A. P.; Mehra, M.; Khanna, S. K.

    1985-01-01

    Amorphous coatings of refractory metal/metalloid-based alloys deposited by magnetron sputtering provide extraordinary hardness and wear resistance. Sputtering target fabricated by thoroughly mixing powders of tungsten, rhenium, and boron in stated proportions and pressing at 1,200 degrees C and 3,000 lb/in. to second power (21 MPa). Substrate lightly etched by sputtering before deposition, then maintained at bias of - 500 V during initial stages of film growth while target material sputtered onto it. Argon gas at pressure used as carrier gas for sputter deposition. Coatings dense, pinhole-free, extremely smooth, and significantly resistant to chemical corrosion in acidic and neutral aqueous environments.

  10. Optical multilayers with an amorphous fluoropolymer

    SciTech Connect

    Chow, R.; Loomis, G.E.; Lindsey, E.F.

    1994-07-01

    Multilayered coatings were made by physical vapor deposition (PVD) of a perfluorinated amorphous polymer, Teflon AF2400, together with other optical materials. A high reflector at 1064 run was made with ZnS and AF2400. An all-organic 1064-nm reflector was made from AF2400 and polyethylene. Oxide (HfO{sub 2}, SiO{sub 2}) compatibility was also tested. Each multilayer system adhered to itself. The multilayers were influenced by coating stress and unintentional temperature rises during PVD deposition.

  11. Tuning Metamaterials by using Amorphous Magnetic Microwires.

    PubMed

    Lopez-Dominguez, V; Garcia, M A; Marin, P; Hernando, A

    2017-08-24

    In this work, we demonstrate theoretically and experimentally the possibility of tuning the electromagnetic properties of metamaterials with magnetic fields by incorporating amorphous magnetic microwires. The large permeability of these wires at microwave frequencies allows tuning the resonance of the metamaterial by using magnetic fields of the order of tens of Oe. We describe here the physical basis of the interaction between a prototypical magnetic metamaterial with magnetic microwires and electromagnetic waves plus providing detailed calculations and experimental results for the case of an array of Split Ring Resonators with Co-based microwires.

  12. Radiation resistance studies of amorphous silicon films

    NASA Technical Reports Server (NTRS)

    Woodyard, James R.; Payson, J. Scott

    1989-01-01

    Hydrogenated amorphous silicon thin films were irradiated with 2.00 MeV helium ions using fluences ranging from 1E11 to 1E15 cm(-2). The films were characterized using photothermal deflection spectroscopy and photoconductivity measurements. The investigations show that the radiation introduces sub-band-gap states 1.35 eV below the conduction band and the states increase supralinearly with fluence. Photoconductivity measurements suggest the density of states above the Fermi energy is not changing drastically with fluence.

  13. Modeling and Simulation of Amorphous Materials

    NASA Astrophysics Data System (ADS)

    Pandey, Anup

    The general and practical inversion of diffraction data - producing a computer model correctly representing the material explored - is an important unsolved problem for disordered materials. Such modeling should proceed by using our full knowledge base, both from experiment and theory. In this dissertation, we introduce a robust method, Force-Enhanced Atomic Refinement (FEAR), which jointly exploits the power of ab initio atomistic simulation along with the information carried by diffraction data. As a preliminary trial, the method has been implemented using empirical potentials for amorphous silicon (a-Si) and silica ( SiO2). The models obtained are comparable to the ones prepared by the conventional approaches as well as the experiments. Using ab initio interactions, the method is applied to two very different systems: amorphous silicon (a-Si) and two compositions of a solid electrolyte memory material silver-doped GeSe3. It is shown that the method works well for both the materials. Besides that, the technique is easy to implement, is faster and yields results much improved over conventional simulation methods for the materials explored. It offers a means to add a priori information in first principles modeling of materials, and represents a significant step toward the computational design of non-crystalline materials using accurate interatomic interactions and experimental information. Moreover, the method has also been used to create a computer model of a-Si, using highly precise X-ray diffraction data. The model predicts properties that are close to the continuous random network models but with no a priori assumptions. In addition, using the ab initio molecular dynamics simulations (AIMD) we explored the doping and transport in hydrogenated amorphous silicon a-Si:H with the most popular impurities: boron and phosphorous. We investigated doping for these impurities and the role of H in the doping process. We revealed the network motion and H hopping induced by

  14. Extremal model for amorphous media plasticity.

    PubMed

    Baret, Jean-Christophe; Vandembroucq, Damien; Roux, Stéphane

    2002-11-04

    An extremal model for the plasticity of amorphous materials is studied in a simple two-dimensional antiplane geometry. The steady state is analyzed through numerical simulations. Long-range spatial and temporal correlations in local slip events are shown to develop, leading to nontrivial and highly anisotropic scaling laws. In particular, the plastic strain is shown to concentrate statistically over a region which tends to align perpendicular to the displacement gradient. By construction, the model can be seen as giving rise to a depinning transition, the threshold of which (i.e., the macroscopic yield stress) also reveals scaling properties reflecting the localization of the activity.

  15. Preparation and characterization of hydrogenated amorphous silicon

    NASA Astrophysics Data System (ADS)

    Donovan, T. M.

    1980-12-01

    Direct current magnetron sputtering was evaluated as a viable approach to producing amorphous SiH thin films for solar photovoltaic applications. It is shown that the optical and transport properties of these films are similar to those of rf diode sputtered material, but the photoresponse and, more importantly, Schottky diode performance are inferior to that already obtained by rd diode sputtering. In order to improve film morphology, ion bombardment was added to the deposition process. Transmission electron microscopy and SIMS measurements are discussed. Optical properties, transport, and photoconductivity of oxygen doped rf diode films are discussed.

  16. Caltech Center for Structural and Amorphous Metals

    DTIC Science & Technology

    2005-05-10

    fracture resistance and subcritical-crack growth behavior in BMG’s and their composites. We have shown that hydrogen significantly increases the glass...Science des Materiaux , 2713], 2002 L. Shadowspeaker, M. B. Shah and R. Busch, "On the crystalline equilibrium phases of the Zr5 7 Nb 5 Cu 15 .4Ni12.6 A lI0...Lowhaphandu, L.A. Ludrosky, and J.J. Lewandowski "Fracture Resistance of Zr-Ti-Ni-Cu-Be Bulk Amorphous Alloy",, TMS-AIME Fall Meeting, Cincinnati, OH

  17. Thermally induced evolution of hydrogenated amorphous carbon

    NASA Astrophysics Data System (ADS)

    Mangolini, Filippo; Rose, Franck; Hilbert, James; Carpick, Robert W.

    2013-10-01

    The thermally induced structural evolution of hydrogenated amorphous carbon (a-C:H) films was investigated in situ by X-ray photoelectron spectroscopy for annealing temperatures up to 500 °C. A model for the conversion of sp3- to sp2-hybridized carbon in a-C:H vs. temperature and time was developed and applied to determine the ranges of activation energies for the thermally activated processes occurring. The energies are consistent with ordering and clustering of sp2 carbon, scission of sp3 carbon-hydrogen bonds and formation of sp2 carbon, and direct transformation of sp3- to sp2-hybridized carbon.

  18. Continuous synthesis of amorphous carbonated apatites.

    PubMed

    Tadic, D; Peters, F; Epple, M

    2002-06-01

    Amorphous carbonated hydroxyapatite was prepared by rapid mixing of aqueous solutions of a continuous computer-controlled reactor. The variation of the carbonate content in the solid product is possible by adjustment of the ratios of phosphate to carbonate in the initial solution. The principal reaction parameters (temperature, pH, stirrer speed, solution composition and supersaturation) are controlled and monitored. By controlling these processing parameters, a non-stoichiometric hydroxyapatite with fine-tuned crystallinity, morphology, and carbonate content can be reproducibly prepared. The higher solubility under the conditions of osteoclastic resorption was tested in vitro at constant pH (4.4).

  19. On the crystallization of amorphous germanium films

    NASA Astrophysics Data System (ADS)

    Edelman, F.; Komem, Y.; Bendayan, M.; Beserman, R.

    1993-06-01

    The incubation time for crystallization of amorphous Ge (a-Ge) films, deposited by e-gun, was studied as a function of temperature between 150 and 500°C by means of both in situ transmission electron microscopy and Raman scattering spectroscopy. The temperature dependence of t0 follows an Arrhenius curve with an activation energy of 2.0 eV for free-sustained a-Ge films. In the case where the a-Ge films were on Si 3N 4 substrate, the activation energy of the incubation process was 1.3 eV.

  20. Optical multilayers with an amorphous fluoropolymer

    NASA Astrophysics Data System (ADS)

    Chow, Robert; Loomis, Gary E.; Lindsey, Edward F.

    1994-09-01

    Multilayered coatings were made by physical vapor deposition (PVD) of a perfluorinated amorphous polymer, Teflon AF2400, together with other optical materials. A high reflector at 1064 nm was made with ZnS and AF2400. An all-organic 1064-nm reflector was made from AF2400 and polyethylene. Oxide (HfO2, SiO2) compatibility was also tested. Each multilayer system adhered to itself. The multilayers were influenced by coating stress and unintentional temperature rises during PVD deposition.

  1. Femtosecond laser crystallization of amorphous Ge

    NASA Astrophysics Data System (ADS)

    Salihoglu, Omer; Kürüm, Ulaş; Yaglioglu, H. Gul; Elmali, Ayhan; Aydinli, Atilla

    2011-06-01

    Ultrafast crystallization of amorphous germanium (a-Ge) in ambient has been studied. Plasma enhanced chemical vapor deposition grown a-Ge was irradiated with single femtosecond laser pulses of various durations with a range of fluences from below melting to above ablation threshold. Extensive use of Raman scattering has been employed to determine post solidification features aided by scanning electron microscopy and atomic force microscopy measurements. Linewidth of the Ge optic phonon at 300 cm-1 as a function of laser fluence provides a signature for the crystallization of a-Ge. Various crystallization regimes including nanostructures in the form of nanospheres have been identified.

  2. Femtosecond laser crystallization of amorphous Ge

    SciTech Connect

    Salihoglu, Omer; Aydinli, Atilla; Kueruem, Ulas; Gul Yaglioglu, H.; Elmali, Ayhan

    2011-06-15

    Ultrafast crystallization of amorphous germanium (a-Ge) in ambient has been studied. Plasma enhanced chemical vapor deposition grown a-Ge was irradiated with single femtosecond laser pulses of various durations with a range of fluences from below melting to above ablation threshold. Extensive use of Raman scattering has been employed to determine post solidification features aided by scanning electron microscopy and atomic force microscopy measurements. Linewidth of the Ge optic phonon at 300 cm{sup -1} as a function of laser fluence provides a signature for the crystallization of a-Ge. Various crystallization regimes including nanostructures in the form of nanospheres have been identified.

  3. Chemical elimination of amorphous carbon on amorphous carbon nanotubes and its electrochemical performance

    NASA Astrophysics Data System (ADS)

    He, Xiaojun; Jiang, Li; Fan, Chuangang; Lei, Jiangwei; Zheng, Mingdong

    2007-04-01

    Chemical elimination of amorphous carbon on amorphous carbon nanotubes (ACNTs) was for the first time investigated by different treatment processes. Electrochemical performance of the modified ACNTs/carbon paste electrode (ACNTs/CPE) was measured by cyclic voltammetry. Field emission scanning and transmission electron microscope (STEM) observation reveals that the diameter of ACNTs is in the range of 60-100 nm. The amorphous nature of ACNTs was proved by the result of Raman analysis. FT-IR spectra showed that it might be one of the low-cost ways to eliminate amorphous carbon on the surface of ACNTs to treat ACNTs with HNO 3 in microwave oven. Further oxidation in air would lead to the decrease of electron transfer rate on the ACNTs/CPE because OH groups on the wall of ACNTs were partly eliminated by oxidation in air. The results of cyclic voltammetry showed that ACNTs/CPE treated with HNO 3 in microwave oven has optimal peak in relation to the highest redox peak current.

  4. In situ evolution of highly dispersed amorphous CoOx clusters for oxygen evolution reaction.

    PubMed

    Chen, Dawei; Dong, Chung-Li; Zou, Yuqin; Su, Dong; Huang, Yu-Cheng; Tao, Li; Dou, Shuo; Shen, Shaohua; Wang, Shuangyin

    2017-08-24

    Electrocatalytic water splitting is a key technique to produce hydrogen fuels, which can be considered as an efficient strategy to store renewable energy. Oxygen evolution reaction (OER) that occurs at the anode side requires a four-electron transfer under highly oxidizing conditions. OER has a large overpotential and therefore determines the overall efficiency. Certain electrocatalysts can efficiently help to improve the reaction kinetics. Owing to the high cost of precious metals such as Pt, Ru, and Ir, non-precious metal oxide catalysts have been vigorously investigated under alkaline conditions. Herein, we synthesized novel highly dispersed amorphous CoOxfor the first time in the form of a cluster favorable to enhance the OER activity using a facile method via the air dielectric barrier discharge (DBD) plasma. Compared with the pristine biopolymer-cobalt complex, the amorphous CoOx cluster exhibits a much higher current density and a lower overpotential for OER, e.g., the overpotential of 290 mV at 10 mA cm(-2) and the overpotential of only 350 mV at 300 mA cm(-1). The excellent electrocatalytic OER activity was attributed to the unsaturated catalytic sites on the amorphous CoOx cluster. In addition, we studied the reaction mechanism, and it was observed that pure O2 DBD plasma could lead to the evolution of crystalline CoOx; however, the presence of N2 and O2 in DBD plasma could ensure the facile evolution of amorphous CoOx clusters. This study provides a new strategy to design amorphous materials for electrocatalysis and beyond.

  5. Cyclic behaviors of amorphous shape memory polymers.

    PubMed

    Yu, Kai; Li, Hao; McClung, Amber J W; Tandon, Gyaneshwar P; Baur, Jeffery W; Qi, H Jerry

    2016-04-07

    Cyclic loading conditions are commonly encountered in the applications of shape memory polymers (SMPs), where the cyclic characteristics of the materials determine their performance during the service life, such as deformation resistance, shape recovery speed and shape recovery ratio. Recent studies indicate that in addition to the physical damage or some other irreversible softening effects, the viscoelastic nature could also be another possible reason for the degraded cyclic behavior of SMPs. In this paper, we explore in detail the influence of the viscoelastic properties on the cyclic tension and shape memory (SM) behavior of an epoxy based amorphous thermosetting polymer. Cyclic experiments were conducted first, which show that although the epoxy material does not have any visible damage or irreversible softening effect during deformation, it still exhibits obvious degradation in the cyclic tension and SM behaviors. A linear multi-branched model is utilized to assist in the prediction and understanding of the mechanical responses of amorphous SMPs. Parametric studies based on the applied model suggest that the shape memory performance can be improved by adjusting programming and recovery conditions, such as lowering the loading rate, increasing the programming temperature, and reducing the holding time.

  6. Structural Characteristics of Synthetic Amorphous Calcium Carbonate

    SciTech Connect

    Michel, F. Marc; MacDonald, Jason; Feng, Jian; Phillips, Brian L.; Ehm, Lars; Tarabrella, Cathy; Parise, John B.; Reeder, Richard J.

    2008-08-06

    Amorphous calcium carbonate (ACC) is an important phase involved in calcification by a wide variety of invertebrate organisms and is of technological interest in the development of functional materials. Despite widespread scientific interest in this phase a full characterization of structure is lacking. This is mainly due to its metastability and difficulties in evaluating structure using conventional structure determination methods. Here we present new findings from the application of two techniques, pair distribution function analysis and nuclear magnetic resonance spectroscopy, which provide new insight to structural aspects of synthetic ACC. Several important results have emerged from this study of ACC formed in vitro using two common preparation methods: (1) ACC exhibits no structural coherence over distances > 15 {angstrom} and is truly amorphous; (2) most of the hydrogen in ACC is present as structural H{sub 2}O, about half of which undergoes restricted motion on the millisecond time scale near room temperature; (3) the short- and intermediate-range structure of ACC shows no distinct match to any known structure in the calcium carbonate system; and (4) most of the carbonate in ACC is monodentate making it distinctly different from monohydrocalcite. Although the structure of synthetic ACC is still not fully understood, the results presented provide an important baseline for future experiments evaluating biogenic ACC and samples containing certain additives that may play a role in stabilization of ACC, crystallization kinetics, and final polymorph selection.

  7. Cryoflotation: densities of amorphous and crystalline ices.

    PubMed

    Loerting, Thomas; Bauer, Marion; Kohl, Ingrid; Watschinger, Katrin; Winkel, Katrin; Mayer, Erwin

    2011-12-08

    We present an experimental method aimed at measuring mass densities of solids at ambient pressure. The principle of the method is flotation in a mixture of liquid nitrogen and liquid argon, where the mixing ratio is varied until the solid hovers in the liquid mixture. The temperature of such mixtures is in the range of 77-87 K, and therefore, the main advantage of the method is the possibility of determining densities of solid samples, which are instable above 90 K. The accessible density range (~0.81-1.40 g cm(-3)) is perfectly suitable for the study of crystalline ice polymorphs and amorphous ices. As a benchmark, we here determine densities of crystalline polymorphs (ices I(h), I(c), II, IV, V, VI, IX, and XII) by flotation and compare them with crystallographic densities. The reproducibility of the method is about ±0.005 g cm(-3), and in general, the agreement with crystallographic densities is very good. Furthermore, we show measurements on a range of amorphous ice samples and correlate the density with the d spacing of the first broad halo peak in diffraction experiments. Finally, we discuss the influence of microstructure, in particular voids, on the density for the case of hyperquenched glassy water and cubic ice samples prepared by deposition of micrometer-sized liquid droplets.

  8. Anisotropic mechanical amorphization drives wear in diamond

    NASA Astrophysics Data System (ADS)

    Pastewka, Lars; Moser, Stefan; Gumbsch, Peter; Moseler, Michael

    2011-01-01

    Diamond is the hardest material on Earth. Nevertheless, polishing diamond is possible with a process that has remained unaltered for centuries and is still used for jewellery and coatings: the diamond is pressed against a rotating disc with embedded diamond grit. When polishing polycrystalline diamond, surface topographies become non-uniform because wear rates depend on crystal orientations. This anisotropy is not fully understood and impedes diamond’s widespread use in applications that require planar polycrystalline films, ranging from cutting tools to confinement fusion. Here, we use molecular dynamics to show that polished diamond undergoes an sp3-sp2 order-disorder transition resulting in an amorphous adlayer with a growth rate that strongly depends on surface orientation and sliding direction, in excellent correlation with experimental wear rates. This anisotropy originates in mechanically steered dissociation of individual crystal bonds. Similarly to other planarization processes, the diamond surface is chemically activated by mechanical means. Final removal of the amorphous interlayer proceeds either mechanically or through etching by ambient oxygen.

  9. Emergent interparticle interactions in thermal amorphous solids

    NASA Astrophysics Data System (ADS)

    Gendelman, Oleg; Lerner, Edan; Pollack, Yoav G.; Procaccia, Itamar; Rainone, Corrado; Riechers, Birte

    2016-11-01

    Amorphous media at finite temperatures, be them liquids, colloids, or glasses, are made of interacting particles that move chaotically due to thermal energy, continuously colliding and scattering off each other. When the average configuration in these systems relaxes only at long times, one can introduce effective interactions that keep the mean positions in mechanical equilibrium. We introduce a framework to determine the effective force laws that define an effective Hessian that can be employed to discuss stability properties and the density of states of the amorphous system. We exemplify the approach with a thermal glass of hard spheres; these experience zero forces when not in contact and infinite forces when they touch. Close to jamming we recapture the effective interactions that at temperature T depend on the gap h between spheres as T /h [C. Brito and M. Wyart, Europhys. Lett. 76, 149 (2006), 10.1209/epl/i2006-10238-x]. For hard spheres at lower densities or for systems whose binary bare interactions are longer ranged (at any density), the emergent force laws include ternary, quaternary, and generally higher-order many-body terms, leading to a temperature-dependent effective Hessian.

  10. Atomic-Scale Imprinting into Amorphous Metals

    NASA Astrophysics Data System (ADS)

    Schwarz, Udo; Li, Rui; Simon, Georg; Kinser, Emely; Liu, Ze; Chen, Zheng; Zhou, Chao; Singer, Jonathan; Osuji, Chinedum; Schroers, Jan

    Nanoimprinting by thermoplastic forming (TPF) has attracted significant attention in recent years due to its promise of low-cost fabrication of nanostructured devices. Usually performed using polymers, amorphous metals have been identified as a material class that might be even better suited for nanoimprinting due to a combination of mechanical properties and processing ability. Commonly referred to as metallic glasses, their featureless atomic structure suggests that there may not be an intrinsic size limit to the material's ability to replicate a mold. To study this hypothesis, we demonstrate atomic-scale imprinting into amorphous metals by TPF under ambient conditions. Atomic step edges of a SrTiO3 (STO) single crystal used as mold were successfully imprinted into Pt-based bulk metallic glasses (BMGs) with high fidelity. Terraces on the BMG replicas possess atomic smoothness with sub-Angstrom roughness that is identical to the one measured on the STO mold. Systematic studies revealed that the quality of the replica depends on the loading rate during imprinting, that the same mold can be used multiple times without degradation of mold or replicas, and that the atomic-scale features on as-imprinted BMG surfaces has impressive long-term stability (months).

  11. Emergent interparticle interactions in thermal amorphous solids.

    PubMed

    Gendelman, Oleg; Lerner, Edan; Pollack, Yoav G; Procaccia, Itamar; Rainone, Corrado; Riechers, Birte

    2016-11-01

    Amorphous media at finite temperatures, be them liquids, colloids, or glasses, are made of interacting particles that move chaotically due to thermal energy, continuously colliding and scattering off each other. When the average configuration in these systems relaxes only at long times, one can introduce effective interactions that keep the mean positions in mechanical equilibrium. We introduce a framework to determine the effective force laws that define an effective Hessian that can be employed to discuss stability properties and the density of states of the amorphous system. We exemplify the approach with a thermal glass of hard spheres; these experience zero forces when not in contact and infinite forces when they touch. Close to jamming we recapture the effective interactions that at temperature T depend on the gap h between spheres as T/h [C. Brito and M. Wyart, Europhys. Lett. 76, 149 (2006)EULEEJ0295-507510.1209/epl/i2006-10238-x]. For hard spheres at lower densities or for systems whose binary bare interactions are longer ranged (at any density), the emergent force laws include ternary, quaternary, and generally higher-order many-body terms, leading to a temperature-dependent effective Hessian.

  12. Amorphous liquid metal electrodes enabled conformable electrochemical therapy of tumors.

    PubMed

    Sun, Xuyang; Yuan, Bo; Rao, Wei; Liu, Jing

    2017-11-01

    Electrochemical treatment of tumors (EChT) has recently been identified as a very effective way for local tumor therapy. However, hindered by the limited effective area of a single rigid electrode, multiple electrodes are often recruited when tackling large tumors, where too many electrodes not only complicate the clinical procedures but also aggravate patients' pain. Here we present a new conceptual electric stimulation tumor therapy through introducing the injectable liquid metal electrodes, which can adapt to complex tumor shapes so as to achieve desired therapeutic performance. This approach can offer evident merits for dealing with the complex physiological situations, especially for those irregular body cavities like stomach, colon, rectum or even blood vessel etc., which are hard to tackle otherwise. As it was disclosed from the conceptual experiments that, Unlike traditional rigid and uncomfortable electrodes, liquid metal possesses high flexibility to attach to any crooked biological position to deliver and adjust targeted electric field to fulfill anticipated tumor destruction. And such amorphous electrodes exhibit rather enhanced treatment effect of tumors. Further, we also demonstrate that EChT with liquid metal electrodes produced more electrochemical products during electrolysis. Transformations with the shapes of liquid metal provided an easily regulatable strategy to improve EChT efficiency, which can conveniently aid to achieve better output compared to multiple electrodes. In vivo EChT of tumors further clarified the effect of liquid metal electrodes in retarding tumor growth and increasing life spans. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Study of irradiation-induced amorphization in intermetallic compounds

    SciTech Connect

    Koike, J.

    1989-01-01

    Irradiation-induced amorphization was studied in situ in the high voltage electron microscope interfaced to a tandem accelerator. Variation of elastic properties during irradiation was studied with Brillouin scattering spectroscopy, and its relation to amorphization were explored. Four important topics were investigated. (1) The temperature dependence of the critical dose for amorphization and its correlation with chemical disordering were studied in CuTi and Zr{sub 3}Al with 1-MeV electron irradiation from 10 to 295 K. Similar temperature dependence was observed in CuTi between the critical dose for amorphization and the chemical disordering rate. Chemical disordering is a major driving force for amorphization. The critical dose for amorphization of Zr{sub 3}Al was twenty times larger than that of CuTi and attributed to the differences in point defect mobility and ordering energy. (2) Projectile mass dependence of amorphization behavior was studied in CuTi irradiated with Ne{sup +},Kr{sup +},Xe{sup +}ions. The dose dependence of the amorphous volume fraction indicated that with increasing mass from Ne{sup +} to Kr{sup +} amorphization kinetics changes from the cascade overlap to the direct-impact amorphization. In relation to the kinetics variation, the critical temperature increased with increasing projectile mass and explained in terms of the thermal stability of the primary damage. (3) Effects of simultaneous and sequential irradiation with Kr+ and electrons were studied in CuTi and Zr{sub 3}Al. Both additive and retardation effects were observed depending on temperature and the electron-to-Kri dose rate ratio and explained as the interaction between point defects and cascade damages. (4) Study of elastic properties during Kr{sup +} irradiation revealed that in FeTi, a large dilation and shear modulus softening accompanied with chemical disordering preceded amorphization, but not observed in NiAl.

  14. Influence of the coat color on the trace elemental status measured by particle-induced X-ray emission in horse hair.

    PubMed

    Asano, Kimi; Suzuki, Kazuyuki; Chiba, Momoko; Sera, Koichiro; Matsumoto, Tsutomu; Asano, Ryuji; Sakai, Takeo

    2005-02-01

    The influence of hair color on the trace elemental status in horse's hair has been studied. A current analytical technique such as particle-induced X-ray emission (PIXE) used in this study has provided reliable, rapid, easy, and relatively inexpensive diagnostic methods. Twenty-eight elements (Al, Br, Ca, Cl, Co, Cu, Cr, Fe, Ga, Hg, K, Mg, Mn, Mo, Na, Nb, Ni, P, Pb, Rb, S, Se, Si, Sr, Ti, V, Y, and Zn) in mane hair were detected by the PIXE method. The gray hair contains significantly greater amounts of Cu, Ti, and Zn, and lower amounts of Br, Ca, Se, and Sr than those in other colored horse hairs (p<0.05). Those results measured in the horse's hair were similar to those found in human and dog hair. When interpreting a result, it should be kept in mind that hair color, especially gray hair, influences the concentrations of some elements in horse hair.

  15. Evaluation of excitation functions of 3He- and α-particle induced reactions on antimony isotopes with special relevance to the production of iodine-124.

    PubMed

    Aslam, M N; Sudár, S; Hussain, M; Malik, A A; Qaim, S M

    2011-01-01

    Cross section data were evaluated for the production of the medically important positron emitter (124)I (T(1/2)=4.18d) via (3)He- and α-particle induced reactions on Sb isotopes. The consistency in the measured data available in the literature was checked against the cross section calculations of three nuclear model codes (i.e. STAPRE, EMPIRE and TALYS). The recommended excitation functions obtained by a statistical procedure were used to derive the integral yields. An assessment of the (124)I yields and associated radioisotopic impurities suggests that the (123)Sb(α,3n)(124)I process over the energy range of E(α)=45 → 32 MeV could be of potential interest for the production of (124)I.

  16. NACRE II: an update of the NACRE compilation of charged-particle-induced thermonuclear reaction rates for nuclei with mass number A<16

    NASA Astrophysics Data System (ADS)

    Xu, Y.; Takahashi, K.; Goriely, S.; Arnould, M.; Ohta, M.; Utsunomiya, H.

    2013-11-01

    An update of the NACRE compilation [3] is presented. This new compilation, referred to as NACRE II, reports thermonuclear reaction rates for 34 charged-particle induced, two-body exoergic reactions on nuclides with mass number A<16, of which fifteen are particle-transfer reactions and the rest radiative capture reactions. When compared with NACRE, NACRE II features in particular (1) the addition to the experimental data collected in NACRE of those reported later, preferentially in the major journals of the field by early 2013, and (2) the adoption of potential models as the primary tool for extrapolation to very low energies of astrophysical S-factors, with a systematic evaluation of uncertainties.

  17. A transmission electron microscopy study of constituent-particle-induced corrosion in 7075-T6 and 2024-T3 aluminum alloys

    SciTech Connect

    Wei, R.P.; Liao, C.M.; Gao, M.

    1998-04-01

    To better understand particle-induced pitting corrosion in aluminum alloys, thin foil specimens of 7075-T6 and 2024-T3 aluminum alloys, with identified constituent particles, were immersed in aerated 0.5M NaCl solution and then examined by transmission electron microscopy (TEM). The results clearly showed matrix dissolution around the iron- and manganese-containing particles (such as Al{sub 23}CuFe{sub 4}), as well as the Al{sub 2}Cu particles. While Al{sub 2}CuMg particles tended to dissolve relative to the matrix, limited local dissolution of the matrix was also observed around these particles. These results are consistent with scanning electron microscopy (SEM) observations of pitting corrosion and are discussed in terms of the electrochemical characteristics of the particles and the matrix.

  18. CORROSION STUDY OF AMORPHOUS METAL RIBBONS

    SciTech Connect

    Lian, T; Day, S D; Farmer, J C

    2006-07-31

    Corrosion costs the Department of Defense billions of dollars every year, with an immense quantity of material in various structures undergoing corrosion. For example, in addition to fluid and seawater piping, ballast tanks, and propulsions systems, approximately 345 million square feet of structure aboard naval ships and crafts require costly corrosion control measures. The use of advanced corrosion-resistant materials to prevent the continuous degradation of this massive surface area would be extremely beneficial. The potential advantages of amorphous metals have been recognized for some time [Latanison 1985]. Iron-based corrosion-resistant, amorphous-metal coatings under development may prove important for maritime applications [Farmer et al. 2005]. Such materials could also be used to coat the entire outer surface of containers for the transportation and long-term storage of spent nuclear fuel, or to protect welds and heat affected zones, thereby preventing exposure to environments that might cause stress corrosion cracking [Farmer et al. 1991, 2000a, 2000b]. In the future, it may be possible to substitute such high-performance iron-based materials for more-expensive nickel-based alloys, thereby enabling cost savings in a wide variety of industrial applications. It should be noted that thermal-spray ceramic coatings have also been investigated for such applications [Haslam et al. 2005]. This report focuses on the corrosion resistance of iron-based melt-spun amorphous metal ribbons. Melt-Spun ribbon is made by rapid solidification--a stream of molten metal is dropped onto a spinning copper wheel, a process that enables the manufacture of amorphous metals which are unable to be manufactured by conventional cold or hot rolling techniques. The study of melt-spun ribbon allows quick evaluation of amorphous metals corrosion resistance. The melt-spun ribbons included in this study are DAR40, SAM7, and SAM8, SAM1X series, and SAM2X series. The SAM1X series ribbons have

  19. Inhibition of titanium-particle-induced inflammatory osteolysis after local administration of dopamine and suppression of osteoclastogenesis via D2-like receptor signaling pathway.

    PubMed

    Yang, Huilin; Xu, Yaozeng; Zhu, Mo; Gu, Ye; Zhang, Wen; Shao, Hongguo; Wang, Yijun; Ping, Zichuan; Hu, Xuanyang; Wang, Liangliang; Geng, Dechun

    2016-02-01

    Chronic inflammation and extensive osteoclast formation play critical roles in wear-debris-induced peri-implant osteolysis. We investigated the potential impact of dopamine on titanium-particle-induced inflammatory osteolysis in vivo and in vitro. Twenty-eight C57BL/6J mice were randomly assigned to four groups: sham control (PBS treatment), titanium (titanium/PBS treatment), low- (titanium/2 μg kg(-1) day(-1) dopamine) and high-dopamine (titanium/10 μg kg(-1) day(-1) dopamine). After 2 weeks, mouse calvariae were collected for micro-computed tomography (micro-CT) and histomorphometry analysis. Bone-marrow-derived macrophages (BMMs) were isolated to assess osteoclast differentiation. Dopamine significantly reduced titanium-particle-induced osteolysis compared with the titanium group as confirmed by micro-CT and histomorphometric data. Osteoclast numbers were 34.9% and 59.7% (both p < 0.01) lower in the low- and high-dopamine-treatment groups, respectively, than in the titanium group. Additionally, low RANKL, tumor necrosis factor-α, interleukin-1β and interleukin-6 immunochemistry staining were noted in dopamine-treatment groups. Dopamine markedly inhibited osteoclast formation, osteoclastogenesis-related gene expression and pro-inflammatory cytokine expression in BMMs in a dose-dependent manner. Moreover, the resorption area was decreased with 10(-9) M and 10(-8) M dopamine to 40.0% and 14.5% (both p < 0.01), respectively. Furthermore, the inhibitory effect of dopamine was reversed by the D2-like-receptor antagonist haloperidol but not by the D1-like-receptor antagonist SCH23390. These results suggest that dopamine therapy could be developed into an effective and safe method for osteolysis-related disease caused by chronic inflammation and excessive osteoclast formation.

  20. Amorphization and nanocrystallization of silcon under shock compression

    DOE PAGES

    Remington, B. A.; Wehrenberg, C. E.; Zhao, S.; ...

    2015-11-06

    High-power, short-duration, laser-driven, shock compression and recovery experiments on [001] silicon unveiled remarkable structural changes above a pressure threshold. Two distinct amorphous regions were identified: (a) a bulk amorphous layer close to the surface and (b) amorphous bands initially aligned with {111} slip planes. Further increase of the laser energy leads to the re-crystallization of amorphous silicon into nanocrystals with high concentration of nano-twins. This amorphization is produced by the combined effect of high magnitude hydrostatic and shear stresses under dynamic shock compression. Shock-induced defects play a very important role in the onset of amorphization. Calculations of the free energymore » changes with pressure and shear, using the Patel-Cohen methodology, are in agreement with the experimental results. Molecular dynamics simulation corroborates the amorphization, showing that it is initiated by the nucleation and propagation of partial dislocations. As a result, the nucleation of amorphization is analyzed qualitatively by classical nucleation theory.« less

  1. Endurance Tests Of Amorphous-Silicon Photovoltaic Modules

    NASA Technical Reports Server (NTRS)

    Ross, Ronald G., Jr.; Sugimura, Russell S.

    1989-01-01

    Failure mechanisms in high-power service studied. Report discusses factors affecting endurance of amorphous-silicon solar cells. Based on field tests and accelerated aging of photovoltaic modules. Concludes that aggressive research needed if amorphous-silicon modules to attain 10-year life - value U.S. Department of Energy established as goal for photovoltaic modules in commercial energy-generating plants.

  2. Superlattice doped layers for amorphous silicon photovoltaic cells

    DOEpatents

    Arya, Rajeewa R.

    1988-01-12

    Superlattice doped layers for amorphous silicon photovoltaic cells comprise a plurality of first and second lattices of amorphous silicon alternatingly formed on one another. Each of the first lattices has a first optical bandgap and each of the second lattices has a second optical bandgap different from the first optical bandgap. A method of fabricating the superlattice doped layers also is disclosed.

  3. Magnetic flux distribution in the amorphous modular transformers

    NASA Astrophysics Data System (ADS)

    Tomczuk, B.; Koteras, D.

    2011-06-01

    3D magnetic fluxes in one-phase and three-phase transformers with amorphous modular cores have been studied. Scalar potentials were implemented for the 3D Finite Element field calculation. Due to the inability to simulate each thin amorphous layer, we introduced supplementary permeabilities along the main directions of magnetization. The calculated fluxes in the cores were tested on the prototypes.

  4. Thermodynamic properties and amorphization of Zr-Si melts

    NASA Astrophysics Data System (ADS)

    Arutyunyan, N. A.; Zaitsev, A. I.; Dunaev, S. F.; Shaposhnikov, N. G.

    2016-02-01

    The relationship between the thermodynamic properties of Zr-Si liquid alloys and their propensity to amorphization is studied. The temperature-concentration dependences of the thermodynamic properties of melts are presented using the concept of associated solutions. It is shown that the range of amorphization coincides with the range of the predominant concentration of Zr3Si associative groups with low formation entropy.

  5. LOW-TEMPERATURE CRYSTALLIZATION OF AMORPHOUS SILICATE IN ASTROPHYSICAL ENVIRONMENTS

    SciTech Connect

    Tanaka, Kyoko K.; Yamamoto, Tetsuo; Kimura, Hiroshi

    2010-07-01

    We construct a theoretical model for low-temperature crystallization of amorphous silicate grains induced by exothermic chemical reactions. As a first step, the model is applied to the annealing experiments, in which the samples are (1) amorphous silicate grains and (2) amorphous silicate grains covered with an amorphous carbon layer. We derive the activation energies of crystallization for amorphous silicate and amorphous carbon from the analysis of the experiments. Furthermore, we apply the model to the experiment of low-temperature crystallization of an amorphous silicate core covered with an amorphous carbon layer containing reactive molecules. We clarify the conditions of low-temperature crystallization due to exothermic chemical reactions. Next, we formulate the crystallization conditions so as to be applicable to astrophysical environments. We show that the present crystallization mechanism is characterized by two quantities: the stored energy density Q in a grain and the duration of the chemical reactions {tau}. The crystallization conditions are given by Q>Q{sub min} and {tau} < {tau}{sub cool} regardless of details of the reactions and grain structure, where {tau}{sub cool} is the cooling timescale of the grains heated by exothermic reactions, and Q{sub min} is minimum stored energy density determined by the activation energy of crystallization. Our results suggest that silicate crystallization occurs in wider astrophysical conditions than hitherto considered.

  6. Addressing the amorphous content issue in quantitative phase analysis

    NASA Astrophysics Data System (ADS)

    Cline, J. P.; Dreele, R. B. Von; Winburn, R.; Stephens, P. W.; Filliben, J. J.

    2011-07-01

    A novel method is used to determine the amorphous content in the certification of NIST standard reference material (SRM) 676a (corundum). Extrapolation of diffraction measurements from mixtures with Si powders of varying surface-to-volume ratio show that approximately 1% by weight of SRM 676a is amorphous.

  7. Method for improving the stability of amorphous silicon

    DOEpatents

    Branz, Howard M.

    2004-03-30

    A method of producing a metastable degradation resistant amorphous hydrogenated silicon film is provided, which comprises the steps of growing a hydrogenated amorphous silicon film, the film having an exposed surface, illuminating the surface using an essentially blue or ultraviolet light to form high densities of a light induced defect near the surface, and etching the surface to remove the defect.

  8. Effect of projectile mass on amorphization of CuTi

    SciTech Connect

    Koike, J.; Okamoto, P.R.; Meshii, M.

    1988-09-01

    Various intermetallic compounds are shown to be amorphized by electron and ion irradiations below a critical temperature. the critical temperature for amorphization is higher for ion irradiation than for electron irradiation. In the present work, the effect of projectile mass is studied in amorphization of CuTi with electron, Ne , Kr and Xe . The critical temperature was found to increase monotonically with projectile mass from 185K for electron to 543K for Kr and Xe . The kinetics of crystalline to amorphous transition was studied by measuring the integrated intensity of diffuse rings on electron diffraction patterns. The analysis of the results of this measurement by Gibbons model indicated that the direct amorphization occurs in a single damage zone with Kr , while overlapping of three damage zones is required for amorphization with Ne . In the light of these observations, the relation between the structure of irradiation damage and the crystalline to amorphous transition, and the projectile mass dependence of the critical temperature for irradiation-induced amorphization will be discussed. 14 refs., 5 figs.

  9. Endurance Tests Of Amorphous-Silicon Photovoltaic Modules

    NASA Technical Reports Server (NTRS)

    Ross, Ronald G., Jr.; Sugimura, Russell S.

    1989-01-01

    Failure mechanisms in high-power service studied. Report discusses factors affecting endurance of amorphous-silicon solar cells. Based on field tests and accelerated aging of photovoltaic modules. Concludes that aggressive research needed if amorphous-silicon modules to attain 10-year life - value U.S. Department of Energy established as goal for photovoltaic modules in commercial energy-generating plants.

  10. Optical conductivity of amorphous Ta and beta-Ta films

    NASA Technical Reports Server (NTRS)

    Nestell, J. E., Jr.; Scoles, K. J.; Christy, R. W.

    1982-01-01

    Tantalum films evaporated in high vacuum onto liquid-nitrogen-cooled substrates had an amorphous structure that persisted even after warming to room temperature. The optical conductivity (as well as the dc conductivity) of the amorphous films differed significantly from that of the bcc films.

  11. Amorphization of SiC under ion and neutron irradiation

    NASA Astrophysics Data System (ADS)

    Snead, L. L.; Zinkle, S. J.; Hay, J. C.; Osborne, M. C.

    1998-05-01

    This paper presents results on the microstructure and physical properties of SiC amorphized by both ion and neutron irradiation. Specifically, 0.56 MeV Si ions have been implanted in single crystal 6H-SiC from ambient through >200°C and the critical threshold for amorphization was measured as a function of the irradiation temperature. From a high resolution transmission electron microscopy (HRTEM) study of the crystalline to amorphous transition region in these materials, elongated pockets of amorphous material oriented parallel to the free surface are observed. Single crystal 6H-SiC and hot pressed and sintered 6H and 3C SiC were neutron irradiated at approximately 70°C to a dose of ˜2.56 dpa causing complete amorphization. Property changes resulting from the crystal to amorphous transition in SiC include a density decrease of 10.8%, a hardness decrease from 38.7 to 21.0 GPa, and a decrease in elastic modulus from 528 to 292 GPa. Recrystallization of the amorphized, single crystal 6H-SiC appears to occur in two stages. In the temperature range of ˜800-1000°C, crystallites nucleate and slowly grow. In the temperature range of 1125-1150°C spontaneous nucleation and rapid growth of crystallites occur. It is further noted that amorphized 6H (alpha) SiC recrystallizes to highly faulted fcc (beta) SiC.

  12. Quantifying Nanoscale Order in Amorphous Materials via Fluctuation Electron Microscopy

    ERIC Educational Resources Information Center

    Bogle, Stephanie Nicole

    2009-01-01

    Fluctuation electron microscopy (FEM) has been used to study the nanoscale order in various amorphous materials. The method is explicitly sensitive to 3- and 4-body atomic correlation functions in amorphous materials; this is sufficient to establish the existence of structural order on the nanoscale, even when the radial distribution function…

  13. Quantifying Nanoscale Order in Amorphous Materials via Fluctuation Electron Microscopy

    ERIC Educational Resources Information Center

    Bogle, Stephanie Nicole

    2009-01-01

    Fluctuation electron microscopy (FEM) has been used to study the nanoscale order in various amorphous materials. The method is explicitly sensitive to 3- and 4-body atomic correlation functions in amorphous materials; this is sufficient to establish the existence of structural order on the nanoscale, even when the radial distribution function…

  14. Electrically conducting ternary amorphous fully oxidized materials and their application

    NASA Technical Reports Server (NTRS)

    Giauque, Pierre (Inventor); Nicolet, Marc (Inventor); Gasser, Stefan M. (Inventor); Kolawa, Elzbieta A. (Inventor); Cherry, Hillary (Inventor)

    2004-01-01

    Electrically active devices are formed using a special conducting material of the form Tm--Ox mixed with SiO2 where the materials are immiscible. The immiscible materials are forced together by using high energy process to form an amorphous phase of the two materials. The amorphous combination of the two materials is electrically conducting but forms an effective barrier.

  15. Polarization effects in femtosecond laser induced amorphization of monocrystalline silicon

    NASA Astrophysics Data System (ADS)

    Bai, Feng; Li, Hong-Jin; Huang, Yuan-Yuan; Fan, Wen-Zhong; Pan, Huai-Hai; Wang, Zhuo; Wang, Cheng-Wei; Qian, Jing; Li, Yang-Bo; Zhao, Quan-Zhong

    2016-10-01

    We have used femtosecond laser pulses to ablate monocrystalline silicon wafer. Raman spectroscopy and X-ray diffraction analysis of ablation surface indicates horizontally polarized laser beam shows an enhancement in amorphization efficiency by a factor of 1.6-1.7 over the circularly polarized laser ablation. This demonstrates that one can tune the amorphization efficiency through the polarization of irradiation laser.

  16. Fabrication and Characterization of Amorphous/Nanocrystalline Thin Film Composite

    NASA Astrophysics Data System (ADS)

    Newton, Benjamin S.

    Combining the absorption abilities of amorphous silicon and the electron transport capabilities of crystalline silicon would be a great advantage to not only solar cells but other semiconductor devices. In this work composite films were created using molecular beam epitaxy and electron beam deposition interchangeably as a method to create metallic precursors. Aluminum induced crystallization techniques were used to convert an amorphous silicon film with a capping layer of aluminum nanodots into a film composed of a mixture of amorphous silicon and nanocrystalline silicon. This layer was grown into the amorphous layer by cannibalizing a portion of the amorphous silicon material during the aluminum induced crystallization. Characterization was performed on films and metallic precursors utilizing SEM, TEM, ellipsometry and spectrophotometer.

  17. Mechanism of solid state amorphization of glucose upon milling.

    PubMed

    Dujardin, N; Willart, J F; Dudognon, E; Danède, F; Descamps, M

    2013-02-07

    Crystalline α-glucose is known to amorphize upon milling at -15 °C while it remains structurally invariant upon milling at room temperature. We have taken advantage of this behavior to compare the microstructural evolutions of the material in both conditions in order to identify the essential microstructural features which drive the amorphization process upon milling. The investigations have been performed by differential scanning calorimetry and by powder X-ray diffraction. The results indicate that two different amorphization mechanisms occur upon milling: an amorphization at the surface of crystallites due to the mechanical shocks and a spontaneous amorphization of the crystallites as they reach a critical size, which is close to 200 Å in the particular case of α-glucose.

  18. Salt Fog Testing Iron-Based Amorphous Alloys

    SciTech Connect

    Rebak, Raul B.; Aprigliano, Louis F.; Day, S. Daniel; Farmer, Joseph C.

    2007-07-01

    Iron-based amorphous alloys are hard and highly corrosion resistant, which make them desirable for salt water and other applications. These alloys can be produced as powder and can be deposited as coatings on any surface that needs to be protected from the environment. It was of interest to examine the behavior of these amorphous alloys in the standard salt-fog testing ASTM B 117. Three different amorphous coating compositions were deposited on 316L SS coupons and exposed for many cycles of the salt fog test. Other common engineering alloys such as 1018 carbon steel, 316L SS and Hastelloy C-22 were also tested together with the amorphous coatings. Results show that amorphous coatings are resistant to rusting in salt fog. Partial devitrification may be responsible for isolated rust spots in one of the coatings. (authors)

  19. Picosecond amorphization of SiO2 stishovite under tension

    PubMed Central

    Misawa, Masaaki; Ryuo, Emina; Yoshida, Kimiko; Kalia, Rajiv K.; Nakano, Aiichiro; Nishiyama, Norimasa; Shimojo, Fuyuki; Vashishta, Priya; Wakai, Fumihiro

    2017-01-01

    It is extremely difficult to realize two conflicting properties—high hardness and toughness—in one material. Nano-polycrystalline stishovite, recently synthesized from Earth-abundant silica glass, proved to be a super-hard, ultra-tough material, which could provide sustainable supply of high-performance ceramics. Our quantum molecular dynamics simulations show that stishovite amorphizes rapidly on the order of picosecond under tension in front of a crack tip. We find a displacive amorphization mechanism that only involves short-distance collective motions of atoms, thereby facilitating the rapid transformation. The two-step amorphization pathway involves an intermediate state akin to experimentally suggested “high-density glass polymorphs” before eventually transforming to normal glass. The rapid amorphization can catch up with, screen, and self-heal a fast-moving crack. This new concept of fast amorphization toughening likely operates in other pressure-synthesized hard solids. PMID:28508056

  20. Picosecond amorphization of SiO2 stishovite under tension.

    PubMed

    Misawa, Masaaki; Ryuo, Emina; Yoshida, Kimiko; Kalia, Rajiv K; Nakano, Aiichiro; Nishiyama, Norimasa; Shimojo, Fuyuki; Vashishta, Priya; Wakai, Fumihiro

    2017-05-01

    It is extremely difficult to realize two conflicting properties-high hardness and toughness-in one material. Nano-polycrystalline stishovite, recently synthesized from Earth-abundant silica glass, proved to be a super-hard, ultra-tough material, which could provide sustainable supply of high-performance ceramics. Our quantum molecular dynamics simulations show that stishovite amorphizes rapidly on the order of picosecond under tension in front of a crack tip. We find a displacive amorphization mechanism that only involves short-distance collective motions of atoms, thereby facilitating the rapid transformation. The two-step amorphization pathway involves an intermediate state akin to experimentally suggested "high-density glass polymorphs" before eventually transforming to normal glass. The rapid amorphization can catch up with, screen, and self-heal a fast-moving crack. This new concept of fast amorphization toughening likely operates in other pressure-synthesized hard solids.

  1. Pressure-Induced Structural Transformation in Radiation-Amorphized Zircon

    SciTech Connect

    Trachenko, Kostya; Dove, Martin T.; Salje, E. K. H.; Brazhkin, V. V.; Tsiok, O. B.

    2007-03-30

    We study the response of a radiation-amorphized material to high pressure. We have used zircon ZrSiO{sub 4} amorphized by natural radiation over geologic times, and have measured its volume under high pressure, using the precise strain-gauge technique. On pressure increase, we observe apparent softening of the material, starting from 4 GPa. Using molecular dynamics simulation, we associate this softening with the amorphous-amorphous transformation accompanied by the increase of local coordination numbers. We observe permanent densification of the quenched sample and a nontrivial 'pressure window' at high temperature. These features point to a new class of amorphous materials that show a response to pressure which is distinctly different from that of crystals.

  2. Pressure-induced structural transformation in radiation-amorphized zircon.

    PubMed

    Trachenko, Kostya; Brazhkin, V V; Tsiok, O B; Dove, Martin T; Salje, E K H

    2007-03-30

    We study the response of a radiation-amorphized material to high pressure. We have used zircon ZrSiO4 amorphized by natural radiation over geologic times, and have measured its volume under high pressure, using the precise strain-gauge technique. On pressure increase, we observe apparent softening of the material, starting from 4 GPa. Using molecular dynamics simulation, we associate this softening with the amorphous-amorphous transformation accompanied by the increase of local coordination numbers. We observe permanent densification of the quenched sample and a nontrivial "pressure window" at high temperature. These features point to a new class of amorphous materials that show a response to pressure which is distinctly different from that of crystals.

  3. Atomistic simulation of damage accumulation and amorphization in Ge

    SciTech Connect

    Gomez-Selles, Jose L. Martin-Bragado, Ignacio; Claverie, Alain; Benistant, Francis

    2015-02-07

    Damage accumulation and amorphization mechanisms by means of ion implantation in Ge are studied using Kinetic Monte Carlo and Binary Collision Approximation techniques. Such mechanisms are investigated through different stages of damage accumulation taking place in the implantation process: from point defect generation and cluster formation up to full amorphization of Ge layers. We propose a damage concentration amorphization threshold for Ge of ∼1.3 × 10{sup 22} cm{sup −3} which is independent on the implantation conditions. Recombination energy barriers depending on amorphous pocket sizes are provided. This leads to an explanation of the reported distinct behavior of the damage generated by different ions. We have also observed that the dissolution of clusters plays an important role for relatively high temperatures and fluences. The model is able to explain and predict different damage generation regimes, amount of generated damage, and extension of amorphous layers in Ge for different ions and implantation conditions.

  4. Construction and characterization of amorphous-silicon test structures

    SciTech Connect

    Koppel, L.N.; Milgram, A.A.

    1987-08-01

    Semiconductor device fabrication and characterization work indicates that construction of amorphous-Si photoconductive radiation detectors is feasible. Amorphous Si films are mechanically stable and adhere well to candidate electrode materials; form Schottky-type rectifying junctions with several electrode metals. Materials exist for forming ohmic contacts on amorphous-Si films. Fabrication facilities accessible to ARACOR produce material of nominal band-gap energy, dangling bond density, and dielectric constant. Modification of amorphous-Si conductivity is feasible and supports the construction of PIN devices. Significant photoconductive response is observed for both Schottky-type and PIN devices, with the latter providing superior performance. It is recommended that construction and experimental evaluation of prototype amorphous-Si radiation detectors be persued in Phase II.

  5. Direct-patterned optical waveguides on amorphous silicon films

    DOEpatents

    Vernon, Steve; Bond, Tiziana C.; Bond, Steven W.; Pocha, Michael D.; Hau-Riege, Stefan

    2005-08-02

    An optical waveguide structure is formed by embedding a core material within a medium of lower refractive index, i.e. the cladding. The optical index of refraction of amorphous silicon (a-Si) and polycrystalline silicon (p-Si), in the wavelength range between about 1.2 and about 1.6 micrometers, differ by up to about 20%, with the amorphous phase having the larger index. Spatially selective laser crystallization of amorphous silicon provides a mechanism for controlling the spatial variation of the refractive index and for surrounding the amorphous regions with crystalline material. In cases where an amorphous silicon film is interposed between layers of low refractive index, for example, a structure comprised of a SiO.sub.2 substrate, a Si film and an SiO.sub.2 film, the formation of guided wave structures is particularly simple.

  6. Amorphous molybdenum sulfides as hydrogen evolution catalysts.

    PubMed

    Morales-Guio, Carlos G; Hu, Xile

    2014-08-19

    Providing energy for a population projected to reach 9 billion people within the middle of this century is one of the most pressing societal issues. Burning fossil fuels at a rate and scale that satisfy our near-term demand will irreversibly damage the living environment. Among the various sources of alternative and CO2-emission-free energies, the sun is the only source that is capable of providing enough energy for the whole world. Sunlight energy, however, is intermittent and requires an efficient storage mechanism. Sunlight-driven water splitting to make hydrogen is widely considered as one of the most attractive methods for solar energy storage. Water splitting needs a hydrogen evolution catalyst to accelerate the rate of hydrogen production and to lower the energy loss in this process. Precious metals such as Pt are superior catalysts, but they are too expensive and scarce for large-scale applications. In this Account, we summarize our recent research on the preparation, characterization, and application of amorphous molybdenum sulfide catalysts for the hydrogen evolution reaction. The catalysts can be synthesized by electrochemical deposition under ambient conditions from readily available and inexpensive precursors. The catalytic activity is among the highest for nonprecious catalysts. For example, at a loading of 0.2 mg/cm(2), the optimal catalyst delivers a current density of 10 mA/cm(2) at an overpotential of 160 mV. The growth mechanism of the electrochemically deposited film catalysts was revealed by an electrochemical quartz microcrystal balance study. While different electrochemical deposition methods produce films with different initial compositions, the active catalysts are the same and are identified as a "MoS(2+x)" species. The activity of the film catalysts can be further promoted by divalent Fe, Co, and Ni ions, and the origins of the promotional effects have been probed. Highly active amorphous molybdenum sulfide particles can also be prepared

  7. Tritiated amorphous silicon films and devices

    NASA Astrophysics Data System (ADS)

    Kosteski, Tome

    The do saddle-field glow discharge deposition technique has been used to bond tritium within an amorphous silicon thin film network using silane and elemental tritium in the glow discharge. The concentration of tritium is approximately 7 at. %. Minimal outgassing of tritium from tritiated hydrogenated amorphous silicon (a-Si:H:T) at room temperature suggests that tritium is bonded stably. Tritium effusion only occurred at temperatures above the film's growth temperature. The radioactive decay of tritium results in the production of high-energy beta particles. Each beta particle can generate on average approximately 1300 electron-hole pairs in a-Si:H:T. Electrical conductivity of a-Si:H:T is shown to be due to a thermally activated process and due to the generation of excess carriers by the beta particles. p-i-n betavoltaic devices have been made with a-Si:H:T in the intrinsic (i-) region. The i-region consisted of either a-Si:H:T, or a thin section of a-Si:H:T (a Delta layer) sandwiched between undoped hydrogenated amorphous silicon (a-Si:H). The excess carriers generated in the i-region are separated by the device's built-in electric field. Short-circuit currents (Isc ), open-circuit voltages (Voc), and power have been measured and correlated to the generation of excess carriers in the i-region. Good devices were made at a substrate temperature of 250°C and relatively large flow rates of silane and tritium; this ensures that there are more monohydride bonds than dihydride bonds. Under dark conditions, Isc, and Voc have been found to decrease rapidly. This is consistent with the production of silicon neutral dangling bonds (5 x 1017cm-3 per day) from the loss of tritium due to its transmutation into helium. Dangling bonds reduce carrier lifetime and weaken the electric field in the i-region. The short-circuit current from Delta layer devices decreased more slowly and settled to higher values for narrower Delta layers. This is because the dangling bonds are

  8. Characteristics of amorphous kerogens fractionated from terrigenous sedimentary rocks

    NASA Astrophysics Data System (ADS)

    Suzuki, Noriyuki

    1984-02-01

    A preliminary attempt to fractionate amorphous kerogens from terrigenous bulk kerogen by a benzene-water two phase partition method under acidic condition was made. Microscopic observation revealed that amorphous kerogens and structured kerogens were fractionated effectively by this method. Characteristics of the amorphous and structured kerogens fractionated by this method were examined by some chemical analyses and compared with those of the bulk kerogen and humic acid isolated from the same rock sample (Haizume Formation, Pleistocene, Japan). The elemental and infrared (IR) analyses showed that the amorphous kerogen fraction had the highest atomic H/C ratio and the lowest atomic N/C ratio and was the richest in aliphatic structures and carbonyl and carboxyl functional groups. Quantities of fatty acids from the saponification products of each geopolymer were in agreement with the results of elemental and IR analyses. Distribution of the fatty acids was suggestive that more animal lipids participate in the formation of amorphous kerogens because of the abundance of relatively lower molecular weight fatty acids (such as C 16 and C 18 acids) in saponification products of amorphous kerogens. On the other hand, although the amorphous kerogen fraction tends to be rich in aliphatic structures compared with bulk kerogen of the same rock samples, van Krevelen plots of elemental compositions of kerogens from the core samples (Nishiyama Oil Field, Tertiary, Japan) reveal that the amorphous kerogen fraction is not necessarily characterized by markedly high atomic H/C ratio. This was attributed to the oxic environment of deposition and the abundance of biodegraded terrestrial amorphous organic matter in the amorphous kerogen fraction used in this work.

  9. High-Density Amorphous Ice, the Frost on Interstellar Grains

    NASA Technical Reports Server (NTRS)

    Jenniskens, P.; Blake, D. F.; Wilson, M. A.; Pohorille, A.

    1995-01-01

    Most water ice in the universe is in a form which does not occur naturally on Earth and of which only minimal amounts have been made in the laboratory. We have encountered this 'high-density amorphous ice' in electron diffraction experiments of low-temperature (T less than 30 K) vapor-deposited water and have subsequently modeled its structure using molecular dynamics simulations. The characteristic feature of high-density amorphous ice is the presence of 'interstitial' oxygen pair distances between 3 and 4 A. However, we find that the structure is best described as a collapsed lattice of the more familiar low-density amorphous form. These distortions are frozen in at temperatures below 38 K because, we propose, it requires the breaking of one hydrogen bond, on average, per molecule to relieve the strain and to restructure the lattice to that of low-density amorphous ice. Several features of astrophysical ice analogs studied in laboratory experiments are readily explained by the structural transition from high-density amorphous ice into low-density amorphous ice. Changes in the shape of the 3.07 gm water band, trapping efficiency of CO, CO loss, changes in the CO band structure, and the recombination of radicals induced by low-temperature UV photolysis all covary with structural changes that occur in the ice during this amorphous to amorphous transition. While the 3.07 micrometers ice band in various astronomical environments can be modeled with spectra of simple mixtures of amorphous and crystalline forms, the contribution of the high-density amorphous form nearly always dominates.

  10. Theoretical studies of amorphous silicon and hydrogenated amorphous silicon with molecular dynamics simulations

    SciTech Connect

    Kwon, I.

    1991-12-20

    Amorphous silicon (a-Si) and hydrogenated amorphous silicon (a-Si:H) have been studied with molecular dynamics simulations. The structural, vibrational, and electronic properties of these materials have been studied with computer-generated structural models and compare well with experimental observations. The stability of a-si and a-Si:H have been studied with the aim of understanding microscopic mechanisms underlying light-induced degradation in a-Si:H (the Staebler-Wronski effect). With a view to understanding thin film growth processes, a-Si films have been generated with molecular dynamics simulations by simulating the deposition of Si-clusters on a Si(111) substrate. A new two- and three-body interatomic potential for Si-H interactions has been developed. The structural properties of a-Si:H networks are in good agreement with experimental measurements. The presence of H atoms reduces strain and disorder relative to networks without H.

  11. Theoretical studies of amorphous silicon and hydrogenated amorphous silicon with molecular dynamics simulations

    SciTech Connect

    Kwon, I.

    1991-12-20

    Amorphous silicon (a-Si) and hydrogenated amorphous silicon (a-Si:H) have been studied with molecular dynamics simulations. The structural, vibrational, and electronic properties of these materials have been studied with computer-generated structural models and compare well with experimental observations. The stability of a-si and a-Si:H have been studied with the aim of understanding microscopic mechanisms underlying light-induced degradation in a-Si:H (the Staebler-Wronski effect). With a view to understanding thin film growth processes, a-Si films have been generated with molecular dynamics simulations by simulating the deposition of Si-clusters on a Si(111) substrate. A new two- and three-body interatomic potential for Si-H interactions has been developed. The structural properties of a-Si:H networks are in good agreement with experimental measurements. The presence of H atoms reduces strain and disorder relative to networks without H.

  12. Amorphous titania/carbon composite electrode materials

    DOEpatents

    Vaughey, John T.; Jansen, Andrew; Joyce, Christopher D.

    2017-05-09

    An isolated salt comprising a compound of formula (H.sub.2X)(TiO(Y).sub.2) or a hydrate thereof, wherein X is 1,4-diazabicyclo[2.2.2]octane (DABCO), and Y is oxalate anion (C.sub.2O.sub.4.sup.-2), when heated in an oxygen-containing atmosphere at a temperature in the range of at least about 275.degree. C. to less than about 400.degree. C., decomposes to form an amorphous titania/carbon composite material comprising about 40 to about 50 percent by weight titania and about 50 to about 60 percent by weight of a carbonaceous material coating the titania. Heating the composite material at a temperature of about 400 to 500.degree. C. crystallizes the titania component to anatase. The titania materials of the invention are useful as components of the cathode or anode of a lithium or lithium ion electrochemical cell.

  13. Tailored magnetic anisotropy in an amorphous trilayer

    NASA Astrophysics Data System (ADS)

    Fu, Yu; Barsukov, I.; Raanaei, H.; Spasova, M.; Lindner, J.; Meckenstock, R.; Farle, M.; Hjörvarsson, B.

    2011-06-01

    An amorphous Co68Fe24Zr8(3 nm)/Al70Zr30(3 nm)/Co68Fe24Zr8(3 nm) trilayer system has been investigated using in-plane and out-of-plane angular dependent ferromagnetic resonance at different frequencies. The in-plane magnetic anisotropy is uniaxial, retaining its value of (2.9 ± 0.1) × 103 J/m3 for each magnetic layer, whereas its direction was tailored independently in an arbitrary manner by applying an external magnetic field during the film deposition. The perpendicular anisotropy constant, supposed to reflect the interface quality, is nearly identical for both layers. Furthermore, the magnetic layers act independently upon each other due to the absence of interlayer coupling.

  14. Spectrometric characterization of amorphous silicon PIN detectors

    NASA Astrophysics Data System (ADS)

    Leyva, A.; Ramírez, F. J.; Ortega, Y.; Estrada, M.; Cabal, A.; Cerdeira, A.; Díaz, A.

    2000-10-01

    During the last years, much interest has been dedicated to the use of amorphous silicon PIN diodes as particle and radiation detectors for medical applications. This work presents the spectrometric characterization of PECVD high deposition rate diodes fabricated at our laboratory, with thickness up to 17.5 μm. Results show that the studied devices detect the Am241 alpha particles and the medical X-rays generated by a mammograph model Senographe 700T from General Electric Possible reasons of the observed energy losses are discussed in the text. Using the SRIM2000 program, the transit of 5.5 MeV alpha particles through a diode was simulated, determining the optimum thickness for these particles to deposit their energy in the intrinsic layer of the diode.

  15. Thermomechanical behavior of amorphous tactic methacrylate polymers

    NASA Technical Reports Server (NTRS)

    Kiran, E.; Gillham, J. K.; Gipstein, E.

    1974-01-01

    Dynamic mechanical spectra of amorphous stereoregular poly(methyl methacrylate)s and poly(t-butyl methacrylate)s with assigned microtacticities are presented and discussed. An intermolecular argument is invoked to account for the higher glass transition temperature of syndiotactic vis a vis isotactic PMMA, in spite of the higher density of the latter at 30 C. An argument is presented to show that the ratio of glassy-region relaxation temperature to glass transition temperature is not only a measure of the degree of coupling of the beta and glass transition processes, but also of the degree to which intermolecular factors influence these processes. The greater extent of the low-temperature irreversibilities observed in the thermomechanical spectra of poly(t-butyl methacrylate)s is attributed to the brittle character induced by the bulky side groups which presumably weaken cohesive forces.

  16. Short range atomic migration in amorphous silicon

    SciTech Connect

    Strauß, F. Jerliu, B.; Geue, T.; Stahn, J.; Schmidt, H.

    2016-05-07

    Experiments on self-diffusion in amorphous silicon between 400 and 500 °C are presented, which were carried out by neutron reflectometry in combination with {sup 29}Si/{sup nat}Si isotope multilayers. Short range diffusion is detected on a length scale of about 2 nm, while long range diffusion is absent. Diffusivities are in the order of 10{sup −19}–10{sup −20} m{sup 2}/s and decrease with increasing annealing time, reaching an undetectable low value for long annealing times. This behavior is strongly correlated to structural relaxation and can be explained as a result of point defect annihilation. Diffusivities for short annealing times of 60 s follow the Arrhenius law with an activation enthalpy of (0.74 ± 0.21) eV, which is interpreted as the activation enthalpy of Si migration.

  17. Radiation resistance studies of amorphous silicon films

    NASA Technical Reports Server (NTRS)

    Payson, J. Scott; Woodyard, James R.

    1988-01-01

    A study of hydrogenated amorphous silicon thin films irradiated with 2.00 MeV helium ions using fluences ranging from 1E11 to 1E15/sq cm is presented. The films were characterized using photothermal deflection spectroscopy, transmission and reflection spectroscopy, and photoconductivity and annealing measurements. Large changes were observed in the subband-gap optical absorption for energies between 0.9 and 1.7 eV. The steady-state photoconductivity showed decreases of almost five orders of magnitude for a fluence of 1E15/sq cm, but the slope of the intensity dependence of the photoconductivity remained almost constant for all fluences. Substantial annealing occurs even at room temperature, and for temperatures greater than 448 K the damage is completely annealed. The data are analyzed to describe the defects and the density of states function.

  18. Negative Magnetoresistance in Amorphous Indium Oxide Wires

    PubMed Central

    Mitra, Sreemanta; Tewari, Girish C; Mahalu, Diana; Shahar, Dan

    2016-01-01

    We study magneto-transport properties of several amorphous Indium oxide nanowires of different widths. The wires show superconducting transition at zero magnetic field, but, there exist a finite resistance at the lowest temperature. The R(T) broadening was explained by available phase slip models. At low field, and far below the superconducting critical temperature, the wires with diameter equal to or less than 100 nm, show negative magnetoresistance (nMR). The magnitude of nMR and the crossover field are found to be dependent on both temperature and the cross-sectional area. We find that this intriguing behavior originates from the interplay between two field dependent contributions. PMID:27876859

  19. Extracting Crystal Chemistry from Amorphous Carbon Structures.

    PubMed

    Deringer, Volker L; Csányi, Gábor; Proserpio, Davide M

    2017-03-08

    Carbon allotropes have been explored intensively by ab initio crystal structure prediction, but such methods are limited by the large computational cost of the underlying density functional theory (DFT). Here we show that a novel class of machine-learning-based interatomic potentials can be used for random structure searching and readily predicts several hitherto unknown carbon allotropes. Remarkably, our model draws structural information from liquid and amorphous carbon exclusively, and so does not have any prior knowledge of crystalline phases: it therefore demonstrates true transferability, which is a crucial prerequisite for applications in chemistry. The method is orders of magnitude faster than DFT and can, in principle, be coupled with any algorithm for structure prediction. Machine-learning models therefore seem promising to enable large-scale structure searches in the future.

  20. Thermal resistance between amorphous silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Meng, Fanhe; Elsahati, Muftah; Liu, Jin; Richards, Robert F.

    2017-05-01

    Nanoparticle-based materials have been used as thermal insulation in a variety of macroscale and microscale applications. In this work, we investigate the heat transfer between nanoparticles using non-equilibrium molecular dynamics simulations. We calculate the total thermal resistance and thermal boundary resistance between adjacent amorphous silica nanoparticles. Numerical results are compared to interparticle resistances determined from experimental measurements of heat transfer across packed silica nanoparticle beds. The thermal resistance between nanoparticles is shown to increase rapidly as the particle contact radius decreases. More significantly, the interparticle resistance depends strongly on the forces between particles, in particular, the presence or absence of chemical bonds between nanoparticles. In addition, the effect of interfacial force strength on thermal resistance increases as the nanoparticle diameter decreases. The simulations results are shown to be in good agreement with experimental results for 20 nm silica nanoparticles.

  1. Amorphous materials molded IR lens progress report

    NASA Astrophysics Data System (ADS)

    Hilton, A. R., Sr.; McCord, James; Timm, Ronald; Le Blanc, R. A.

    2008-04-01

    Amorphous Materials began in 2000 a joint program with Lockheed Martin in Orlando to develop molding technology required to produce infrared lenses from chalcogenide glasses. Preliminary results were reported at this SPIE meeting by Amy Graham1 in 2003. The program ended in 2004. Since that time, AMI has concentrated on improving results from two low softening glasses, Amtir 4&5. Both glasses have been fully characterized and antireflection coatings have been developed for each. Lenses have been molded from both glasses, from Amtir 6 and from C1 Core glass. A Zygo unit is used to evaluate the results of each molded lens as a guide to improving the molding process. Expansion into a larger building has provided room for five production molding units. Molded lens sizes have ranged from 8 mm to 136 mm in diameter. Recent results will be presented

  2. Negative Magnetoresistance in Amorphous Indium Oxide Wires

    NASA Astrophysics Data System (ADS)

    Mitra, Sreemanta; Tewari, Girish C.; Mahalu, Diana; Shahar, Dan

    2016-11-01

    We study magneto-transport properties of several amorphous Indium oxide nanowires of different widths. The wires show superconducting transition at zero magnetic field, but, there exist a finite resistance at the lowest temperature. The R(T) broadening was explained by available phase slip models. At low field, and far below the superconducting critical temperature, the wires with diameter equal to or less than 100 nm, show negative magnetoresistance (nMR). The magnitude of nMR and the crossover field are found to be dependent on both temperature and the cross-sectional area. We find that this intriguing behavior originates from the interplay between two field dependent contributions.

  3. Mechanism of boron diffusion in amorphous silicon.

    PubMed

    Mirabella, Salvatore; De Salvador, Davide; Bruno, Elena; Napolitani, Enrico; Pecora, Emanuele F; Boninelli, Simona; Priolo, Francesco

    2008-04-18

    We have elucidated the mechanism for B migration in the amorphous (a-) Si network. B diffusivity in a-Si is much higher than in crystalline Si; it is transient and increases with B concentration up to 2 x 10(20) B/cm(3). At higher density, B atoms in a-Si quickly precipitate. B diffusion is indirect, mediated by dangling bonds (DB) present in a-Si. The density of DB is enhanced by B accommodation in the a-Si network and decreases because of a-Si relaxation. Accurate data simulations allow one to extract the DB diffusivity, whose activation energy is 2.6 eV. Implications of these results are discussed.

  4. Tunable plasticity in amorphous silicon carbide films.

    PubMed

    Matsuda, Yusuke; Kim, Namjun; King, Sean W; Bielefeld, Jeff; Stebbins, Jonathan F; Dauskardt, Reinhold H

    2013-08-28

    Plasticity plays a crucial role in the mechanical behavior of engineering materials. For instance, energy dissipation during plastic deformation is vital to the sufficient fracture resistance of engineering materials. Thus, the lack of plasticity in brittle hybrid organic-inorganic glasses (hybrid glasses) often results in a low fracture resistance and has been a significant challenge for their integration and applications. Here, we demonstrate that hydrogenated amorphous silicon carbide films, a class of hybrid glasses, can exhibit a plasticity that is even tunable by controlling their molecular structure and thereby leads to an increased and adjustable fracture resistance in the films. We decouple the plasticity contribution from the fracture resistance of the films by estimating the "work-of-fracture" using a mean-field approach, which provides some insight into a potential connection between the onset of plasticity in the films and the well-known rigidity percolation threshold.

  5. Yield strain in shear banding amorphous solids.

    PubMed

    Dasgupta, Ratul; Hentschel, H George E; Procaccia, Itamar

    2013-02-01

    In recent research it was found that the fundamental shear-localizing instability of amorphous solids under external strain, which eventually results in a shear band and failure, consists of a highly correlated array of Eshelby quadrupoles all having the same orientation and some density ρ. In this paper we calculate analytically the energy E(ρ,γ) associated with such highly correlated structures as a function of the density ρ and the external strain γ. We show that for strains smaller than a characteristic strain γ(Y) the total strain energy initially increases as the quadrupole density increases, but that for strains larger than γ(Y) the energy monotonically decreases with quadrupole density. We identify γ(Y) as the yield strain. Its value, derived from values of the qudrupole strength based on the atomistic model, agrees with that from the computed stress-strain curves and broadly with experimental results.

  6. Structural relaxation of vacancies in amorphous silicon

    SciTech Connect

    Kim, E.; Lee, Y.H.; Chen, C.; Pang, T.

    1997-07-01

    The authors have studied the structural relaxation of vacancies in amorphous silicon (a-Si) using a tight-binding molecular-dynamics method. The most significant difference between vacancies in a-Si and those in crystalline silicon (c-Si) is that the deep gap states do not show up in a-Si. This difference is explained through the unusual behavior of the structural relaxation near the vacancies in a-Si, which enhances the sp{sup 2} + p bonding near the band edges. They have also observed that the vacancies do not migrate below 450 K although some of them can still be annihilated, particularly at high defect density due to large structural relaxation.

  7. Polarization Stability of Amorphous Piezoelectric Polyimides

    NASA Technical Reports Server (NTRS)

    Park, C.; Ounaies, Z.; Su, J.; Smith, J. G., Jr.; Harrison, J. S.

    2000-01-01

    Amorphous polyimides containing polar functional groups have been synthesized and investigated for potential use as high temperature piezoelectric sensors. The thermal stability of the piezoelectric effect of one polyimide was evaluated as a function of various curing and poling conditions under dynamic and static thermal stimuli. First, the polymer samples were thermally cycled under strain by systematically increasing the maximum temperature from 50 C to 200 C while the piezoelectric strain coefficient was being measured. Second, the samples were isothermally aged at an elevated temperature in air, and the isothermal decay of the remanent polarization was measured at room temperature as a function of time. Both conventional and corona poling methods were evaluated. This material exhibited good thermal stability of the piezoelectric properties up to 100 C.

  8. Amorphous silicon-based microchannel plates

    NASA Astrophysics Data System (ADS)

    Franco, Andrea; Riesen, Yannick; Wyrsch, Nicolas; Dunand, Sylvain; Powolny, François; Jarron, Pierre; Ballif, Christophe

    2012-12-01

    Microchannel plates (MCP) based on hydrogenated amorphous silicon (a-Si:H) were recently introduced to overcome some of the limitations of crystalline silicon and glass MCP. The typical thickness of a-Si:H based MCPs (AMCP) ranges between 80 and 100 μm and the micromachining of the channels is realized by deep reactive ion etching (DRIE). Advantages and issues regarding the fabrication process are presented and discussed. Electron amplification is demonstrated and analyzed using Electron Beam Induced Current (EBIC) technique. The gain increases as a function of the bias voltage, limited to -340 V on account of high leakage currents across the structure. EBIC maps on 10° tilted samples confirm that the device active area extend to the entire channel opening. AMCP characterization with the electron beam shows gain saturation and signal quenching which depends on the effectiveness of the charge replenishment in the channel walls.

  9. Nanostructural characterization of amorphous diamondlike carbon films

    SciTech Connect

    SIEGAL,MICHAEL P.; TALLANT,DAVID R.; MARTINEZ-MIRANDA,L.J.; BARBOUR,J. CHARLES; SIMPSON,REGINA L.; OVERMYER,DONALD L.

    2000-01-27

    Nanostructural characterization of amorphous diamondlike carbon (a-C) films grown on silicon using pulsed-laser deposition (PLD) is correlated to both growth energetic and film thickness. Raman spectroscopy and x-ray reflectivity probe both the topological nature of 3- and 4-fold coordinated carbon atom bonding and the topographical clustering of their distributions within a given film. In general, increasing the energetic of PLD growth results in films becoming more ``diamondlike'', i.e. increasing mass density and decreasing optical absorbance. However, these same properties decrease appreciably with thickness. The topology of carbon atom bonding is different for material near the substrate interface compared to material within the bulk portion of an a-C film. A simple model balancing the energy of residual stress and the free energies of resulting carbon topologies is proposed to provide an explanation of the evolution of topographical bonding clusters in a growing a-C film.

  10. Bulk amorphous steels based on Fe alloys

    DOEpatents

    Lu, ZhaoPing; Liu, Chain T.

    2006-05-30

    A bulk amorphous alloy has the approximate composition: Fe.sub.(100-a-b-c-d-e)Y.sub.aMn.sub.bT.sub.cM.sub.dX.sub.e wherein: T includes at least one of the group consisting of: Ni, Cu, Cr and Co; M includes at least one of the group consisting of W, Mo, Nb, Ta, Al and Ti; X includes at least one of the group consisting of Co, Ni and Cr; a is an atomic percentage, and a<5; b is an atomic percentage, and b.ltoreq.25; c is an atomic percentage, and c.ltoreq.25; d is an atomic percentage, and d.ltoreq.25; and e is an atomic percentage, and 5.ltoreq.e.ltoreq.30.

  11. Differences in gene expression and cytokine production by crystalline vs. amorphous silica in human lung epithelial cells

    PubMed Central

    2012-01-01

    Background Exposure to respirable crystalline silica particles, as opposed to amorphous silica, is associated with lung inflammation, pulmonary fibrosis (silicosis), and potentially with lung cancer. We used Affymetrix/GeneSifter microarray analysis to determine whether gene expression profiles differed in a human bronchial epithelial cell line (BEAS 2B) exposed to cristobalite vs. amorphous silica particles at non-toxic and equal surface areas (75 and 150 × 106μm2/cm2). Bio-Plex analysis was also used to determine profiles of secreted cytokines and chemokines in response to both particles. Finally, primary human bronchial epithelial cells (NHBE) were used to comparatively assess silica particle-induced alterations in gene expression. Results Microarray analysis at 24 hours in BEAS 2B revealed 333 and 631 significant alterations in gene expression induced by cristobalite at low (75) and high (150 × 106μm2/cm2) amounts, respectively (p < 0.05/cut off ≥ 2.0-fold change). Exposure to amorphous silica micro-particles at high amounts (150 × 106μm2/cm2) induced 108 significant gene changes. Bio-Plex analysis of 27 human cytokines and chemokines revealed 9 secreted mediators (p < 0.05) induced by crystalline silica, but none were induced by amorphous silica. QRT-PCR revealed that cristobalite selectively up-regulated stress-related genes and cytokines (FOS, ATF3, IL6 and IL8) early and over time (2, 4, 8, and 24 h). Patterns of gene expression in NHBE cells were similar overall to BEAS 2B cells. At 75 × 106μm2/cm2, there were 339 significant alterations in gene expression induced by cristobalite and 42 by amorphous silica. Comparison of genes in response to cristobalite (75 × 106μm2/cm2) revealed 60 common, significant gene alterations in NHBE and BEAS 2B cells. Conclusions Cristobalite silica, as compared to synthetic amorphous silica particles at equal surface area concentrations, had comparable effects on the viability of human bronchial epithelial cells

  12. Phyllosilicates and Amorphous Gel in the Nakhlites

    NASA Astrophysics Data System (ADS)

    Hicks, L. J.; Bridges, J. C.; Gurman, S. J.

    2013-09-01

    Previous studies of the nakhlite martian meteorites have revealed hydrothermal minerals present within the fractures of the olivine minerals and the mesostasis. The olivine fractures of the Lafayette nakhlite reveal variations with initial deposits of siderite on the fracture walls, followed by crystalline phyllosilicates (smectite), and finishing with a rapidly cooled amorphous silicate gel within the central regions of the fractures. The mesostasis fractures of Lafayette also contain a crystalline phyllosilicate (serpentine). The amorphous gel is the most abundant secondary phase within the fractures of the other nakhlites [1, 2]. By studying nine nakhlite samples, including Lafayette, Governador Valadares, Nakhla, Y-000593, Y-000749, Miller-Range 03346, NWA 817, NWA 998, and NWA 5790, our aim is to constrain the identity of the phyllosilicate secondary phase minerals found throughout the nakhlite martian meteorites. This is achieved using methods including Electron Probe Micro-analysis (EPMA); X-ray Absorption Near-Edge Structure (Fe-K XANES) spectroscopy measured using Beamline I-18 at the Diamond Light Source synchrotron; and the use of Transmission Electron Microscopy (TEM) at the University of Leicester for High-Resolution (HR) imaging and Selected Area Electron Diffraction (SAED). BF studying nine nakhlite samples, including Lafayette, Governador Valadares, Nakhla, Y-000593, Y-000749, Miller-Range 03346, NWA 817, NWA 998, and NWA 5790, our aim is to constrain the identity of the phyllosilicate secondary phase minerals found throughout the nakhlite martian meteorites. This is achieved using methods including Electron Probe Micro-analysis (EPMA); X-ray Absorption Near-Edge Structure (Fe-K XANES) spectroscopy measured using Beamline I-18 at the Diamond Light Source synchrotron; and the use of Transmission Electron Microscopy (TEM) at the University of Leicester for High-Resolution (HR) imaging and Selected Area Electron Diffraction (SAED).

  13. Castable Amorphous Metal Mirrors and Mirror Assemblies

    NASA Technical Reports Server (NTRS)

    Hofmann, Douglas C.; Davis, Gregory L.; Agnes, Gregory S.; Shapiro, Andrew A.

    2013-01-01

    A revolutionary way to produce a mirror and mirror assembly is to cast the entire part at once from a metal alloy that combines all of the desired features into the final part: optical smoothness, curvature, flexures, tabs, isogrids, low CTE, and toughness. In this work, it has been demonstrated that castable mirrors are possible using bulk metallic glasses (BMGs, also called amorphous metals) and BMG matrix composites (BMGMCs). These novel alloys have all of the desired mechanical and thermal properties to fabricate an entire mirror assembly without machining, bonding, brazing, welding, or epoxy. BMGs are multi-component metal alloys that have been cooled in such a manner as to avoid crystallization leading to an amorphous (non-crystalline) microstructure. This lack of crystal structure and the fact that these alloys are glasses, leads to a wide assortment of mechanical and thermal properties that are unlike those observed in crystalline metals. Among these are high yield strength, carbide-like hardness, low melting temperatures (making them castable like aluminum), a thermoplastic processing region (for improving smoothness), low stiffness, high strength-to-weight ratios, relatively low CTE, density similar to titanium alloys, high elasticity and ultra-smooth cast parts (as low as 0.2-nm surface roughness has been demonstrated in cast BMGs). BMGMCs are composite alloys that consist of a BMG matrix with crystalline dendrites embedded throughout. BMGMCs are used to overcome the typically brittle failure observed in monolithic BMGs by adding a soft phase that arrests the formation of cracks in the BMG matrix. In some cases, BMGMCs offer superior castability, toughness, and fatigue resistance, if not as good a surface finish as BMGs. This work has demonstrated that BMGs and BMGMCs can be cast into prototype mirrors and mirror assemblies without difficulty.

  14. Amorphous-amorphous transformation at high pressure in gallo-germanosilicate tetrahedral network glasses

    NASA Astrophysics Data System (ADS)

    Cormier, L.; Ferlat, G.; Itié, J.-P.; Galoisy, L.; Calas, G.; Aquilanti, G.

    2007-10-01

    We report the existence of structurally distinct amorphous states upon compression in sodium gallo-germanosilicate glasses. In situ x-ray absorption spectroscopy provides clear evidence for a transition at high pressure to a more compact arrangement of atoms based on Ga and Ge octahedral sites. This study extends previous works on simple and open tetrahedral networks ( SiO2 and GeO2 ) by showing the compression behavior of stuffed (by Na cations) and mixed network glasses.

  15. Anomalous hopping conduction in nanocrystalline/amorphous composites and amorphous semiconductor thin films

    NASA Astrophysics Data System (ADS)

    Kakalios, James; Bodurtha, Kent

    Composite nanostructured materials consisting of nanocrystals (nc) embedded within a thin film amorphous matrix can exhibit novel opto-electronic properties. Composite films are synthesized in a dual-chamber co-deposition PECVD system capable of producing nanocrystals of material A and embedding then within a thin film matrix of material B. Electronic conduction in composite thin films of hydrogenated amorphous silicon (a-Si:H) containing nc-germanium or nc-silicon inclusions, as well as in undoped a-Si:H, does not follow an Arrhenius temperature dependence, but rather is better described by an anomalous hopping expression (exp[-(To/T)3/4) , as determined from the ``reduced activation energy'' proposed by Zabrodskii and Shlimak. This temperature dependence has been observed in other thin film resistive materials, such as ultra-thin disordered films of Ag, Bi, Pb and Pd; carbon-black polymer composites; and weakly coupled Au and ZnO quantum dot arrays. There is presently no accepted theoretical understanding of this expression. The concept of a mobility edge, accepted for over four decades, appears to not be necessary to account for charge transport in amorphous semiconductors. Supported by NSF-DMR and the Minnesota Nano Center.

  16. Defects in Amorphous Silicon: Dynamics and Role on Crystallization.

    NASA Astrophysics Data System (ADS)

    Shin, Jung Hoon

    Defects play a crucial role in determining the properties of many materials of scientific and technological interest. With ion irradiation, it is possible to controllably inject defects, and thus carefully study the dynamics of defect creation and annihilation, as well as the effects such defect injection has on materials properties and phase transformations. Amorphous silicon is a model system for the study of amorphous solids characterized as continuous random networks. In hydrogenated form, it is an important material for semiconductor devices such as solar cells and thin film transistors. It is the aim of this thesis to elucidate the dynamics of defects in an amorphous silicon matrix, and the role such defects can play on crystallization of amorphous silicon. In the first chapter, the concept of a continuous random network that characterizes amorphous silicon is presented as an introduction to amorphous silicon. Structural relaxation, or annihilation of non-equilibrium defects in an amorphous matrix, is introduced. Also developed are the concept of the activation energy spectrum theory for structural relaxation of amorphous solids and the density of relaxation states. In the second chapter, the density of relaxation states for the structural relaxation of amorphous silicon is measured by measuring changes in electrical conductivity, using ion irradiation and thermal anneal to create and annihilate defects, respectively. A new quantitative model for defect creation and annihilation, termed the generalized activation energy spectrum theory, is developed in Chapter 3, and is found to be superior to previous models in describing defect dynamics in amorphous silicon. In Chapter 4, the effect of irradiation on the crystallization of amorphous silicon is investigated. It is found that irradiation affects crystallization even when the growth kinetics of crystal grains is unaffected, and that defects injected into amorphous matrix by irradiation probably play a role in

  17. Approaches to determine the enthalpy of crystallisation, and amorphous content, of lactose from isothermal calorimetric data.

    PubMed

    Dilworth, Sarah E; Buckton, Graham; Gaisford, Simon; Ramos, Rita

    2004-10-13

    Amorphous lactose will crystallise rapidly if its glass transition temperature is reduced below its storage temperature. This is readily achieved by storing samples at ambient temperature and a relative humidity (RH) of greater than 50%. If the sample is monitored in an isothermal microcalorimeter as it crystallises, the heat changes associated with the event can be measured; indeed this is one of the methods used to quantify the amorphous content of powders and formulations. However, variations in the calculation methods used to determine these heat changes have led to discrepancies in the values reported in the literature and frequently make comparison of data from different sources difficult. Data analysis and peak integration software allow the selection and integration of specific areas of complex traces with great reproducibility; this has led to the observation that previously ignored artefacts are in fact of sufficient magnitude to affect calculated enthalpies. In this work a number of integration methodologies have been applied to the analysis of amorphous spray-dried lactose, crystallised under 53 or 75% RH at 25 degrees C. The data allowed the selection of a standard methodology from which reproducible heat changes could be determined. The method was subsequently applied to the analysis of partially amorphous lactose samples (containing 1-100% (w/w) amorphous content) allowing the quantification limit of the technique to be established. It was found that the best approach for obtaining reproducible results was (i) to crystallise under an RH of 53%, because this slowed the crystallisation response allowing better experimental measurement and (ii) to integrate all the events occurring in the ampoule, rather than trying to select only that region corresponding to crystallisation, since it became clear that the processes occurring in the cell overlapped and could not be deconvoluted. The technique was able to detect amorphous contents as low as 1% (w

  18. Amorphous Calcium Carbonate Based-Microparticles for Peptide Pulmonary Delivery.

    PubMed

    Tewes, Frederic; Gobbo, Oliviero L; Ehrhardt, Carsten; Healy, Anne Marie

    2016-01-20

    Amorphous calcium carbonate (ACC) is known to interact with proteins, for example, in biogenic ACC, to form stable amorphous phases. The control of amorphous/crystalline and inorganic/organic ratios in inhalable calcium carbonate microparticles may enable particle properties to be adapted to suit the requirements of dry powders for pulmonary delivery by oral inhalation. For example, an amorphous phase can immobilize and stabilize polypeptides in their native structure and amorphous and crystalline phases have different mechanical properties. Therefore, inhalable composite microparticles made of inorganic (i.e., calcium carbonate and calcium formate) and organic (i.e., hyaluronan (HA)) amorphous and crystalline phases were investigated for peptide and protein pulmonary aerosol delivery. The crystalline/amorphous ratio and polymorphic form of the inorganic component was altered by changing the microparticle drying rate and by changing the ammonium carbonate and HA initial concentration. The bioactivity of the model peptide, salmon calcitonin (sCT), coprocessed with alpha-1-antitrypsin (AAT), a model protein with peptidase inhibitor activity, was maintained during processing and the microparticles had excellent aerodynamic properties, making them suitable for pulmonary aerosol delivery. The bioavailability of sCT after aerosol delivery as sCT and AAT-loaded composite microparticles to rats was 4-times higher than that of sCT solution.

  19. Irradiation-induced amorphization of AlPO 4

    NASA Astrophysics Data System (ADS)

    Sreeram, A. N.; Hobbs, L. W.; Bordes, N.; Ewing, R. C.

    1996-08-01

    AlPO 4, in the mineral form berlinite, is isostructural with α-quartz. We have investigated the irradiation-induced amorphization of hydrothermally-grown berlinite and found that — like quartz and other silicas but unlike most other phosphates — it undergoes solid-state radiolyis, with an efficiency fifty times that of quartz at room temperature, and amorphizes at an absorbed ionization dose of about 1 GGy. High-resolution TEM revealed that — unlike quartz in which small amorphous inclusions nucleate — electron-irradiated AlPO 4 proceeds uniformly to an aperiodic state, much as do cristobalite and tridymite, and 20 times faster. It was found also to amorphize under 1.5 MeV Kr + ion irradiation at a collisional energy density (10 eV/atom) similar to that for quartz and in keeping with the degree of structural freedom afforded by its tetrahedral network structure. The critical ion fluence for amorphization was found to increase by a factor of 5 between 300 and 600 K. Radial distribution functions derived from energy-filtered electron diffraction patterns from regions amorphized by electrons resemble those of electron-amorphized quartz with some additional features.

  20. Unveiling descriptors for predicting the bulk modulus of amorphous carbon

    NASA Astrophysics Data System (ADS)

    Takahashi, Keisuke; Tanaka, Yuzuru

    2017-02-01

    Descriptors for the bulk modulus of amorphous carbon are investigated through the implementation of data mining where data sets are prepared using first-principles calculations. Data mining reveals that the number of bonds in each C atom and the density of amorphous carbon are found to be descriptors representing the bulk modulus. Support vector regression (SVR) within machine learning is implemented and descriptors are trained where trained SVR is able to predict the bulk modulus of amorphous carbon. An inverse problem, starting from the bulk modulus towards structural information of amorphous carbon, is performed and structural information of amorphous carbon is successfully predicted from the desired bulk modulus. Thus, treating several physics factors in multidimensional space allows for the prediction of physical phenomena. In addition, the reported approach proposes that "big data" can be generated from a small data set using machine learning if descriptors are well defined. This would greatly change how amorphous carbon would be treated and help accelerate further development of amorphous carbon materials.

  1. Infrared Spectroscopy and Optical Constants of Porous Amorphous Solid Water

    SciTech Connect

    Cholette, Francois; Zubkov, Tykhon; Smith, R. Scott; Dohnalek, Zdenek; Kay, Bruce D.; Ayotte, Patrick

    2009-04-02

    Reflection-absorption infrared spectra (RAIRS) of amorphous solid water (ASW) films grown at 20K on a Pt(111) substrate at various incidence angle (θBeam = 0-85o) using a molecular beam are reported. They display complex features arising from the interplay between refraction, absorption within the sample, and interference effects between the multiple reflections at the film-substrate and film-vacuum interfaces. Using a simple classical optics model based on Fresnel equations, we obtain optical constants [i.e., n(ω) and k(ω)] for porous ASW in the 1000-4000cm-1 (10-2.5 μm) range. The behaviour of the optical properties of ASW in the intramolecular OH stretching region with increasing θBeam is shown to be strongly correlated with its decreasing density and increasing surface area. A direct comparison between the RAIRS and calculated vibrational spectra shows a large difference (~200cm-1) in the position of the coupled H-bonded intramolecular OH stretching vibrations spectral feature. Moreover, this band shifts in opposite directions with increasing θBeam in RAIRS and vibrational spectra demonstrating RAIRS spectra cannot be interpreted straightforwardly as vibrational spectra due to severe optical distortions from refraction and interference effects.

  2. Wake potential of swift ion in amorphous carbon target

    NASA Astrophysics Data System (ADS)

    Al-Bahnam, Nabil janan; Ahmad, Khalid A.; Aboo Al-Numan, Abdullah Ibrahim

    2017-02-01

    The wake potential and wake phenomena for swift proton in an amorphous carbon target were studied by utilising various dielectric function formalisms, including the Drude dielectric function, the Drude-Lorentz dielectric function and quantum dielectric function. The Drude model results exhibited a damped oscillatory behaviour in the longitudinal direction behind the projectile; the pattern of these oscillations decreases exponentially in the transverse direction. In addition, the wake potential extends slightly ahead of the projectile which also depends on the proton coordinate and velocity. The effect of electron binding on the wake potential, characterised by the ratio ωp2 / ω02 = 10 to 0.1, has been studied alongside the Drude-Lorentz dielectric function and quantum dielectric function formalisms; the results evidently show that the wake potential dip depth decreases with more oscillations when the electron density ratio ωp2 / ω02 decreases from 10 to 0.1. One of the primary objectives of the present work is to construct a reasonably realistic procedure for simulating the response of target to swift ions by combining an expression for the induced wake potential along with several important dielectric function models; the aim of this research is to reduce computational complexity without sacrificing accuracy. This is regarded as being an efficient strategy in that it creates suitable computer simulation procedures which are relevant to actual solids. After comparing this method with other models, the main differences and similarities have been noted while the end results have proved encouraging.

  3. Superoxide-mediated dissolution of amorphous ferric oxyhydroxide in seawater.

    PubMed

    Fujii, Manabu; Rose, Andrew L; Waite, T David; Omura, Tatsuo

    2006-02-01

    We have investigated the kinetics of superoxide-mediated dissolution of amorphous ferric oxyhydroxide (AFO) in seawater by spectrophotometrically examining the rate of formation of a ferrous-ferrozine complex (Fe(II)(FZ)3) with particular attention given to the effect of aging and iron concentration on the rate of superoxide-mediated dissolution of AFO. The production rates of Fe(II)(FZ)3 decreased with aging of AFO for iron concentrations from 50 to 500 nM, indicating that changes to the chemical and physical properties of AFO affected the reactivity of inorganic ferric iron species with superoxide. A kinetic model developed by assuming that Fe(II)' formation is preceded by the thermal dissolution of AFO provided a good description of the Fe(II)(FZ)3 production rates over time. First-order rate constants for Fe(II)' formation were found to depend on the total iron concentration, suggesting that superoxide-mediated Fe(II) reduction is affected not only by the rate of thermal dissolution of AFO but also by the rate of AFO precipitation. The reported high rates of superoxide production by both photochemical and biotic pathways in aquatic systems coupled with the ability of superoxide to dissolve freshly formed ferric oxides suggest that this process may have a significant impact on the biogeochemical cycling of iron, especially if organisms have an affinity for ferrous iron.

  4. Semaphorin-3a, neuropilin-1 and plexin-A1 in prosthetic-particle induced bone loss.

    PubMed

    Saad, S; Dharmapatni, A A S S K; Crotti, T N; Cantley, M D; Algate, K; Findlay, D M; Atkins, G J; Haynes, D R

    2016-01-01

    Peri-prosthetic osteolysis (PPO) occurs in response to prosthetic wear particles causing an inflammatory reaction in the surrounding tissue that leads to subsequent bone loss. Semaphorin-3a (SEM3A), neuropilin-1 (NRP1) and plexin-A1 (PLEXA1) are axonal guidance molecules that have been recently implicated in regulating bone metabolism. This study investigated SEM3A, NRP1 and PLEXA1 protein and mRNA expression in human PPO tissue and polyethylene (PE) particle-stimulated human peripheral blood mononuclear cell (PBMC)-derived osteoclasts in vitro. In addition, the effects of tumour necrosis factor alpha (TNFα) on cultured osteoclasts was assessed. In PPO tissues, a granular staining pattern of SEM3A and NRP1 was observed within large multi-nucleated cells that contained prosthetic wear particles. Immunofluorescent staining confirmed the expression of SEM3A, NRP1 and PLEXA1 in large multi-nucleated human osteoclasts in vitro. Furthermore, SEM3A, NRP1 and PLEXA1 mRNA levels progressively increased throughout osteoclast differentiation induced by receptor activator of nuclear factor κB ligand (RANKL), and the presence of PE particles further increased mRNA expression of all three molecules. Soluble SEM3A was detected in human osteoclast culture supernatant at days 7 and 17 of culture, as assessed by ELISA. TNFα treatment for 72h markedly decreased the mRNA expression of SEM3A, NRP1 and PLEXA1 by human osteoclasts in vitro. Our findings suggest that SEM3A, NRP1 and PLEXA1 may have important roles in PPO, and their interactions, alone or as a complex, may have a role in pathological bone loss progression. Peri-prosthetic osteolysis occurs in response to prosthetic wear particles causing an inflammatory reaction in the surrounding tissue that leads to subsequent bone loss. The rate of hip and knee arthroplasty is increasing by at least 5% per year. However, these joint replacements have a finite lifespan, with data from the National Joint Replacement Registry (Australia

  5. Health hazards due to the inhalation of amorphous silica.

    PubMed

    Merget, R; Bauer, T; Küpper, H U; Philippou, S; Bauer, H D; Breitstadt, R; Bruening, T

    2002-01-01

    Occupational exposure to crystalline silica dust is associated with an increased risk for pulmonary diseases such as silicosis, tuberculosis, chronic bronchitis, chronic obstructive pulmonary disease (COPD) and lung cancer. This review summarizes the current knowledge about the health effects of amorphous (non-crystalline) forms of silica. The major problem in the assessment of health effects of amorphous silica is its contamination with crystalline silica. This applies particularly to well-documented pneumoconiosis among diatomaceous earth workers. Intentionally manufactured synthetic amorphous silicas are without contamination of crystalline silica. These synthetic forms may be classified as (1) wet process silica, (2) pyrogenic ("thermal" or "fumed") silica, and (3) chemically or physically modified silica. According to the different physicochemical properties, the major classes of synthetic amorphous silica are used in a variety of products, e.g. as fillers in the rubber industry, in tyre compounds, as free-flow and anti-caking agents in powder materials, and as liquid carriers, particularly in the manufacture of animal feed and agrochemicals; other uses are found in toothpaste additives, paints, silicon rubber, insulation material, liquid systems in coatings, adhesives, printing inks, plastisol car undercoats, and cosmetics. Animal inhalation studies with intentionally manufactured synthetic amorphous silica showed at least partially reversible inflammation, granuloma formation and emphysema, but no progressive fibrosis of the lungs. Epidemiological studies do not support the hypothesis that amorphous silicas have any relevant potential to induce fibrosis in workers with high occupational exposure to these substances, although one study disclosed four cases with silicosis among subjects exposed to apparently non-contaminated amorphous silica. Since the data have been limited, a risk of chronic bronchitis, COPD or emphysema cannot be excluded. There is no study

  6. On the Plasticity of Amorphous Solids

    NASA Astrophysics Data System (ADS)

    Lin, Jie

    Mechanical behaviors of amorphous materials under external stress are central to various phenomena including earthquakes and landslides. Most amorphous materials possess a well defined yield stress when thermal fluctuations are negligible. Only when the shear stress is above the yield stress, the material can flow as a fluid, otherwise it deforms as a solid. There are accumulating evidences that the yielding transition between the flowing and solid phase is a critical phenomenon, and one evidence is the long ranged correlations of plastic strain during adiabatic shear. In spite of this, we still have not fully understood the associated critical exponents and their scaling relations. In the last decade, it has been widely accepted that the elementary rearrangements in amorphous solids are not well-defined topological defects as crystals, instead they are local irreversible rearrangements of a few particles, denoted as shear transformations. Because a single shear transformation changes the local arrangement of particles, it therefore generates an elastic stress field propagating over the whole system. The resulting changes in the local stresses in other regions of the system may in turn trigger more shear transformations. A central feature that complicates the yielding transition is the long range and anisotropic stress field generated by shear transformations. This peculiar interaction between shear transformations leads to two important characteristics: 1.the mechanical noises generated by plastic deformation are broadly distributed 2.those regions that are undergoing plastic deformation has equal probability to make other parts of the material to be more stable or more unstable, depending on the direction between them. In this thesis, we show that these two important factors leads to a singular density of shear transformations, P( x) xtheta at small x, where x is a local measure of stability, namely, the extra stress one needs to add locally to reach the elastic

  7. Encapsulation of tea tree oil by amorphous beta-cyclodextrin powder.

    PubMed

    Shrestha, Meena; Ho, Thao M; Bhandari, Bhesh R

    2017-04-15

    An innovative method to encapsulate tea tree oil (TTO) by direct complexation with solid amorphous beta-cyclodextrin (β-CD) was investigated. A β-CD to TTO ratio of 90.5:9.5 (104.9mg TTO/g β-CD) was used in all complexation methods. The encapsulation was performed by direct mixing, and direct mixing was followed by the addition of water (13-17% moisture content, MC) or absolute ethanol (1:1, 1:2, 1:3 and 1:4 TTO:ethanol). The direct mixing method complexed the lowest amount of TTO (60.77mg TTO/g β-CD). Powder recrystallized using 17% MC included 99.63mg of TTO/g β-CD. The addition of ethanol at 1:2 and 1:3 TTO:ethanol ratios resulted in the inclusion of 94.3 and 98.45mg of TTO/g β-CD respectively, which was similar to that of TTO encapsulated in the conventional paste method (95.56mg TTO/g β-CD), suggesting an effective solid encapsulation method. The XRD and DSC results indicated that the amorphous TTO-β-CD complex was crystallized by the addition of water and ethanol.

  8. Application of mesoporous silicon dioxide and silicate in oral amorphous drug delivery systems.

    PubMed

    Qian, Ken K; Bogner, Robin H

    2012-02-01

    Aqueous solubility of an active pharmaceutical ingredient is an important consideration to ensure successful drug development. Mesoporous materials have been investigated as an amorphous drug delivery system owing to their nanosized capillaries and large surface areas. The complex interactions of crystalline compounds with mesoporous media and their implication in drug delivery are not well understood. Molecules interacting with porous media behave very differently than those in bulk phase. Their altered dynamics and thermodynamics play an important role in the properties and product performance of the amorphous system. In this review, application of mesoporous silicon dioxide and silicates in drug amorphization is the main focus. First, as background, the nature of gas-porous media interactions is summarized. The synthesis of various types of mesoporous silica, which are used by many investigators in this field, is described. Second, the behavior of molecules confined in mesopores is compared with those in bulk, crystalline phase. The molecular dynamics of compounds due to confinement, analyzed using various techniques, and their consequences in drug delivery are discussed. Finally, the preparation and performance of drug delivery systems using mesoporous silica are examined.

  9. On the thermodynamically stable amorphous phase of polymer-derived silicon oxycarbide

    NASA Astrophysics Data System (ADS)

    Yu, Liping; Raj, Rishi

    2015-09-01

    A model for the thermodynamic stability of amorphous silicon oxycarbide (SiCO) is presented. It builds upon the reasonably accepted model of SiCO which is conceived as a nanodomain network of graphene. The domains are expected to be filled with SiO2 molecules, while the interface with graphene is visualized to contain mixed bonds described as Si bonded to C as well as to O atoms. Normally these SiCO compositions would be expected to crystallize. Instead, calorimetric measurements have shown that the amorphous phase is thermodynamically stable. In this article we employ first-principles calculations to estimate how the interfacial energy of the graphene networks is favorably influenced by having mixed bonds attached to them. We analyze the ways in which this reduction in interfacial energy can stabilize the amorphous phase. The approach highlights how density functional theory computations can be combined with the classical analysis of phase transformations to explain the behavior of a complex material. In addition we discover a two-dimensional lattice structure, with the composition Si2C4O3 that is constructed from a single layer of graphene congruent with silicon and oxygen bonds on either side.

  10. Wavelength prediction of laser incident on amorphous silicon detector by neural network

    NASA Astrophysics Data System (ADS)

    Esmaeili Sani, V.; Moussavi-Zarandi, A.; Kafaee, M.

    2011-10-01

    In this paper we present a method based on artificial neural networks (ANN) and the use of only one amorphous semiconductor detector to predict the wavelength of incident laser. Amorphous semiconductors and especially amorphous hydrogenated silicon, a-Si:H, are now widely used in many electronic devices, such as solar cells, many types of position sensitive detectors and X-ray imagers for medical applications. In order to study the electrical properties and detection characteristics of thin films of a-Si:H, n-i-p structures have been simulated by SILVACO software. The basic electronic properties of most of the materials used are known, but device modeling depends on a large number of parameters that are not all well known. In addition, the relationship between the shape of the induced anode current and the wavelength of the incident laser leads to complicated calculations. Soft data-based computational methods can model multidimensional non-linear processes and represent the complex input-output relation between the form of the output signal and the wavelength of incident laser.

  11. On the thermodynamically stable amorphous phase of polymer-derived silicon oxycarbide

    PubMed Central

    Yu, Liping; Raj, Rishi

    2015-01-01

    A model for the thermodynamic stability of amorphous silicon oxycarbide (SiCO) is presented. It builds upon the reasonably accepted model of SiCO which is conceived as a nanodomain network of graphene. The domains are expected to be filled with SiO2 molecules, while the interface with graphene is visualized to contain mixed bonds described as Si bonded to C as well as to O atoms. Normally these SiCO compositions would be expected to crystallize. Instead, calorimetric measurements have shown that the amorphous phase is thermodynamically stable. In this article we employ first-principles calculations to estimate how the interfacial energy of the graphene networks is favorably influenced by having mixed bonds attached to them. We analyze the ways in which this reduction in interfacial energy can stabilize the amorphous phase. The approach highlights how density functional theory computations can be combined with the classical analysis of phase transformations to explain the behavior of a complex material. In addition we discover a two-dimensional lattice structure, with the composition Si2C4O3 that is constructed from a single layer of graphene congruent with silicon and oxygen bonds on either side. PMID:26419962

  12. Soluble iron modulates iron oxide particle-induced inflammatory responses via prostaglandin E2 synthesis: In vitro and in vivo studies

    PubMed Central

    2009-01-01

    Background Ambient particulate matter (PM)-associated metals have been shown to play an important role in cardiopulmonary health outcomes. To study the modulation of PM-induced inflammation by leached off metals, we investigated intracellular solubility of radio-labeled iron oxide (59Fe2O3) particles of 0.5 and 1.5 μm geometric mean diameter. Fe2O3 particles were examined for the induction of the release of interleukin 6 (IL-6) as pro-inflammatory and prostaglandin E2 (PGE2) as anti-inflammatory markers in cultured alveolar macrophages (AM) from Wistar Kyoto (WKY) rats. In addition, we exposed male WKY rats to monodispersed Fe2O3 particles by intratracheal instillation (1.3 or 4.0 mg/kg body weight) to examine in vivo inflammation. Results Particles of both sizes are insoluble extracellularly in the media but moderately soluble in AM with an intracellular dissolution rate of 0.0037 ± 0.0014 d-1 for 0.5 μm and 0.0016 ± 0.0012 d-1 for 1.5 μm 59Fe2O3 particles. AM exposed in vitro to 1.5 μm particles (10 μg/mL) for 24 h increased IL-6 release (1.8-fold; p < 0.05) and also PGE2 synthesis (1.9-fold; p < 0.01). By contrast, 0.5 μm particles did not enhance IL-6 release but strongly increased PGE2 synthesis (2.5-fold, p < 0.005). Inhibition of PGE2 synthesis by indomethacin caused a pro-inflammatory phenotype as noted by increased IL-6 release from AM exposed to 0.5 μm particles (up to 3-fold; p < 0.005). In the rat lungs, 1.5 but not 0.5 μm particles (4.0 mg/kg) induced neutrophil influx and increased vascular permeability. Conclusions Fe2O3 particle-induced neutrophilic inflammatory response in vivo and pro-inflammatory cytokine release in vitro might be modulated by intracellular soluble iron via PGE2 synthesis. The suppressive effect of intracellular released soluble iron on particle-induced inflammation has implications on how ambient PM-associated but soluble metals influence pulmonary toxicity of ambient PM. PMID:20028532

  13. Alpha particle-induced bystander effect is mediated by ROS via a p53-dependent SCO2 pathway in hepatoma cells.

    PubMed

    Li, Jitao; He, Mingyuan; Shen, Bo; Yuan, Dexiao; Shao, Chunlin

    2013-12-01

    The radiation-induced bystander effect (RIBE) has important implications for the efficiency of radiotherapy but the underlying role of cellular metabolism is widely unknown. The roles of synthesis of cytochrome c oxidase 2 (SCO2), a key effector for respiratory chain, and related signaling factors in α-particle-induced bystander damage were currently investigated in a liver cell co-culture system. Human hepatoma cells of HepG2 with wild-type p53 (wtp53) and Hep3B (p53 null) were irradiated with 0.4 Gy of α-particles and co-cultured with non-irradiated normal liver cells HL-7702 for 6 h, then the incidence of micronucleus (MN) in the bystander HL-7702 cells was analyzed. The expressions of total P53, phospho-P53 (p-P53), SCO2, and reactive oxygen species (ROS) in the irradiated hepatoma cells were detected. In some experiments, the hepatoma cells were respectively treated with p53 siRNA, SCO2 siRNA, or dimethyl sulfoxide (DMSO) before irradiation. Bystander damage in HL-7702 cells was induced by α-irradiated HepG2 cells but not by α-irradiated Hep3B cells, and this bystander effect was diminished when the irradiated HepG2 cells were pretreated with p53 siRNA, SCO2 siRNA, or DMSO. Meanwhile, the expressions of p-P53 protein and SCO2 mRNA, the activity of SCO2 protein, and intracellular ROS were all increased in the irradiated HepG2 cells but not Hep3B cells and these expressions were eliminated by p53 siRNA treatment. Moreover, the radiation-enhanced expressions of SCO2 and ROS were inhibited by SCO2 siRNA. α-particle-induced bystander effect was regulated by p53 and its downstream SCO2 in the irradiated hepatoma cells, and ROS generation could be an early event for triggering this bystander response.

  14. Molecular Relaxations in Supercooled Liquid and Glassy States of Amorphous Quinidine: Dielectric Spectroscopy and Density Functional Theory Approaches.

    PubMed

    Schammé, Benjamin; Mignot, Mélanie; Couvrat, Nicolas; Tognetti, Vincent; Joubert, Laurent; Dupray, Valérie; Delbreilh, Laurent; Dargent, Eric; Coquerel, Gérard

    2016-08-04

    In this article, we conduct a comprehensive molecular relaxation study of amorphous Quinidine above and below the glass-transition temperature (Tg) through broadband dielectric relaxation spectroscopy (BDS) experiments and theoretical density functional theory (DFT) calculations, as one major issue with the amorphous state of pharmaceuticals is life expectancy. These techniques enabled us to determine what kind of molecular motions are responsible, or not, for the devitrification of Quinidine. Parameters describing the complex molecular dynamics of amorphous Quinidine, such as Tg, the width of the α relaxation (βKWW), the temperature dependence of α-relaxation times (τα), the fragility index (m), and the apparent activation energy of secondary γ relaxation (Ea-γ), were characterized. Above Tg (> 60 °C), a medium degree of nonexponentiality (βKWW = 0.5) was evidenced. An intermediate value of the fragility index (m = 86) enabled us to consider Quinidine as a glass former of medium fragility. Below Tg (< 60 °C), one well-defined secondary γ relaxation, with an apparent activation energy of Ea-γ = 53.8 kJ/mol, was reported. From theoretical DFT calculations, we identified the most reactive part of Quinidine moieties through exploration of the potential energy surface. We evidenced that the clearly visible γ process has an intramolecular origin coming from the rotation of the CH(OH)C9H14N end group. An excess wing observed in amorphous Quinidine was found to be an unresolved Johari-Goldstein relaxation. These studies were supplemented by sub-Tg experimental evaluations of the life expectancy of amorphous Quinidine by X-ray powder diffraction and differential scanning calorimetry. We show that the difference between Tg and the onset temperature for crystallization, Tc, which is 30 K, is sufficiently large to avoid recrystallization of amorphous Quinidine during 16 months of storage under ambient conditions.

  15. Ceramic oxides: Surfaces and amorphous/crystalline interfaces

    NASA Astrophysics Data System (ADS)

    Gilliss, Shelley Rae

    Model studies have been carried out to further the basic understanding of ceramic oxide surfaces and the interface between ceramic oxides and amorphous films. Boundary-migration studies using model geometries of alumina and rutile bicrystals have been carried out. In the case of the rutile boundary, migration proceeds faster near the surface, while in the alumina bicrystal migration proceeds faster away from the boundary. A solution/reprecipitation mechanism is proposed for the alumina case, while a mechanism similar to diffusion-induced grain boundary migration (DIGM) is proposed for the rutile case. Three distinct faceting behaviors for the m-plane of alumina have been identified. The low-energy configuration was observed within a glass droplet whereas higher-energy configurations were observed outside dewet droplets and within a migrating grain boundary. These high-energy configurations are due to kinetic limitations. A method for monitoring the evolution of faceting over the course of several heat treatments has been developed which uses a combination of visible-light microscopy (VLM) and atomic-force microscopy (AFM) with the aid of fiducial marks (indentations) as reference markers. Grooves at migrating grain boundaries in high-purity alumina have been studied using a combination of VLM, AFM, and transmission electron microscopy (TEM) through a progression of heat treatments at 1650°C. The partial angles of grooves that developed at migrating grain boundaries were found to be asymmetric compared with those that developed at stationary boundaries. The wetting behavior of an amorphous SiO2 film on single-crystal substrates of TiO2 has been extensively studied. A model involving the initiation of an instability due to surface-tension gradients is proposed as the mechanism for the complex patterns observed. It is proposed that the surface-tension gradients are caused by the changing composition of the SiO 2 thin film due to dissolution of the TiO2 substrate into

  16. The 'depletion layer' of amorphous p-n junctions

    NASA Technical Reports Server (NTRS)

    Von Roos, O.

    1981-01-01

    It is shown that within reasonable approximations for the density of state distribution within the mobility gap of a:Si, a one-to-one correspondence exists between the electric field distribution in the transition region of an amorphous p-n junction and that in the depletion layer of a crystalline p-n junction. Thus it is inferred that the depletion layer approximation which leads to a parabolic potential distribution within the depletion layer of crystalline junctions also constitutes a fair approximation in the case of amorphous junctions. This fact greatly simplifies an analysis of solid-state electronic devices based on amorphous material (i.e., solar cells).

  17. Deuterium magnetic resonance studies in amorphous and crystalline silicon

    NASA Astrophysics Data System (ADS)

    Borzi, Raffaella

    Hydrogenation is essential for useful amorphous silicon films and devices. We used deuteron magnetic resonance (DMR) to investigate the hydrogen microstructure in amorphous and crystalline silicon. DMR line shapes analyses and longitudinal relaxation time studies can distinguish silicon-bonded deuterons from molecular deuterons. Our comparisons between crystalline and amorphous silicon have yielded new perspectives on the characterization of molecular hydrogen sites including interstitial tetragonal T-sites, and microvoids. Quantitative analyses of DMR line shapes and spin populations show that the fraction of interstitially trapped molecular hydrogen increases with increasing photovoltaic quality of the films.

  18. Amorphous Silicates in Primitive Meteoritic Materials: Acfer 094 and IDPs

    NASA Technical Reports Server (NTRS)

    Keller, L. P.; Nakamura-Messenger, K.; Messenger, S.; Walker, Robert M.

    2009-01-01

    The abundance of presolar grains is one measure of the primitive nature of meteoritic materials. Presolar silicates are abundant in meteorites whose matrices are dominated by amorphous silicates such as the unique carbonaceous chondrite Acfer 094. Presolar silicates are even more abundant in chondritic-porous interplanetary dust particles (CP-IDPs). Amorphous silicates in the form of GEMS (glass with embedded metal and sulfides) grains are a major component of CP IDPs. We are studying amorphous silicates in Acfer 094 matrix in order to determine whether they are related to the GEMS grains in CPIDPs

  19. Gold nanoparticles promote amorphous carbon to be ammonia gas sensor

    NASA Astrophysics Data System (ADS)

    Hsu, Hua-Shu; Ju, Shin-Pon; Sun, Shih-Jye; Chou, Hsiung; Chia, C. H.

    2016-05-01

    As gold-nanoparticles-embedded in amorphous carbon films the sp 3 carbon orbits near the interface will be partially transferred to sp 2. The Raman spectrum measurements as well as the molecular-dynamics simulations used the second reactive empirical bond order (REBO) potential simulating the interatomic force between carbon atoms both confirm the orbital transformations. The amorphous carbon films are initially inert to gases, while the films embedded with gold nanoparticles exhibit the increase of resistance in ammonia atmosphere. Namely, gold-nanoparticles-embedded amorphous carbon films become the candidate for ammonia gas sensor materials.

  20. Structures of surface and interface of amorphous ice

    NASA Astrophysics Data System (ADS)

    Kumagai, Yu; Ikeda-Fukazawa, Tomoko

    2017-06-01

    To investigate the surface structure, we performed molecular dynamics calculations of amorphous ice. The result shows that a low density layer, which forms a few hydrogen bonds with weaker strength, exists in the surface. Furthermore, the sintering processes were simulated to investigate the structure of grain boundary formed from the adsorption of two surfaces. The result indicates that a low density region exists in a boundary between amorphous ice grains. The structures of surface and interface of amorphous ice have important implications for adsorption, diffusion, and chemical reaction in ice grains of interstellar molecular clouds.

  1. Amorphization of C-implanted Fe(Cr) alloys

    SciTech Connect

    Knapp, J.A.; Follstaedt, D.M.; Sorensen, N.R.; Pope, L.E.

    1990-01-01

    The amorphous phase formed by implanting C into Fe alloyed with Cr, which is prototype for the amorphous phase formed by implanting C into stainless steels, is compared to that formed by implanting C plus Ti into Fe and steels. The composition range of the phase has been examined; higher Cr and C concentrations are required than needed with Ti and C. The friction and wear benefits obtained by implanting stainless steels with C alone do not persist for the long durations and high wear loads found with Ti and C. However, the amorphous Fe-Cr-C alloys exhibits good aqueous corrosion resistance. 9 refs., 3 figs., 1 tabs.

  2. Robust hydrophobic Fe-based amorphous coating by thermal spraying

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Wu, Y.; Liu, L.

    2012-09-01

    Metallic surface is intrinsically hydrophilic due to its high surface energy. In this work, we present a different picture that highly hydrophobic metallic coatings could be directly fabricated by thermal spraying of Fe-based amorphous powders through the surface roughness control. These hydrophobic coatings are amorphous, exhibiting super-high hardness and excellent corrosion resistance. With low surface energy modification, the coatings become superhydrophobic and exhibit clearly self-cleaning effect. The present work opens a window for the applications of the amorphous coatings.

  3. Photoemission studies of amorphous silicon induced by P + ion implantation

    NASA Astrophysics Data System (ADS)

    Petö, G.; Kanski, J.

    1995-12-01

    An amorphous Si layer was formed on a Si (1 0 0) surface by P + implantation at 80 keV. This layer was investigated by means of photoelectron spectroscopy. The resulting spectra are different from earlier spectra on amorphous Si prepared by e-gun evaporation or cathode sputtering. The differences consist of a decreased intensity in the spectral region corresponding to p-states, and appearace of new states at higher binding energy. Qualitativity similar results have been reported for Sb implanted amorphous Ge and the modification seems to be due to the changed short range order.

  4. Amorphous photonic crystals with only short-range order.

    PubMed

    Shi, Lei; Zhang, Yafeng; Dong, Biqin; Zhan, Tianrong; Liu, Xiaohan; Zi, Jian

    2013-10-04

    Distinct from conventional photonic crystals with both short- and long-range order, amorphous photonic crystals that possess only short-range order show interesting optical responses owing to their unique structural features. Amorphous photonic crystals exhibit unique light scattering and transport, which lead to a variety of interesting phenomena such as isotropic photonic bandgaps or pseudogaps, noniridescent structural colors, and light localization. Recent experimental and theoretical advances in the study of amorphous photonic crystals are summarized, focusing on their unique optical properties, artificial fabrication, bionspiration, and potential applications. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Nonaffinity in amorphous solids close to the jamming transition

    NASA Astrophysics Data System (ADS)

    Arévalo, Roberto; Pica Ciamarra, Massimo

    2017-06-01

    Nonaffinity is known to be an integral part of the response of amorphous solids. Its role is particularly relevant in particulate systems close to their jamming transition, where it dominates the elastic response. Thus, to determine the elastic properties of amorphous solids it is essential to rationalize the features of their nonaffine response. Via numerical simulations we investigate the relation between the non affine response and the vibrational properties of model amorphous materials. We show that, contrary to previous speculations, modes below the Boson peak are those mostly responsible for the nonaffine response.

  6. Amorphous Semiconductors: From Photocatalyst to Computer Memory

    NASA Astrophysics Data System (ADS)

    Sundararajan, Mayur

    Amorphous semiconductors are useful in many applications like solar cells, thin film displays, sensors, electrophotography, etc. The dissertation contains four projects. In the first three projects, semiconductor glasses which are a subset of amorphous semiconductors were studied. The last project is about exploring the strengths and constraints of two analysis programs which calculate the particle size information from experimental Small Angle X-ray Scattering data. By definition, glasses have a random atomic arrangement with no order beyond the nearest neighbor, but strangely there exists an Intermediate Range Order (IRO). The origin of IRO is still not clearly understood, but various models have been proposed. The signature of IRO is the First Sharp Diffraction Peak(FSDP) observed in x-ray and neutron scattering data. The FSDP of TiO 2 SiO2 glass photocatalyst with different Ti:Si ratio from SAXS data was measured to test the theoretical models. The experimental results along with its computer simulation results strongly supported one of two leading models. It was also found that the effect of doping IRO on TiO2 SiO2 is severe in mesoporous form than the bulk form. Glass semiconductors in mesoporous form are very useful photocatalysts due to their large specific surface area. Solar energy conversion of photocatalysts greatly depends on their bandgap, but very few photocatalysts have the optical bandgap covering the whole visible region of solar spectrum leading to poor efficiency. A physical method was developed to manipulate the bandgap of mesoporous photocatalysts, by using the anisotropic thermal expansion and stressed glass network properties of mesoporous glasses. The anisotropic thermal expansion was established by S/WAXS characterization of mesoporous silica (MCM-41). The residual stress in the glass network of mesoporous glasses was already known for an earlier work. The new method was initially applied on mesoporous TiPO4, and the results were

  7. Electronic transport in mixed-phase hydrogenated amorphous/nanocrystalline silicon thin films

    NASA Astrophysics Data System (ADS)

    Wienkes, Lee Raymond

    Interest in mixed-phase silicon thin film materials, composed of an amorphous semiconductor matrix in which nanocrystalline inclusions are embedded, stems in part from potential technological applications, including photovoltaic and thin film transistor technologies. Conventional mixed-phase silicon films are produced in a single plasma reactor, where the conditions of the plasma must be precisely tuned, limiting the ability to adjust the film and nanoparticle parameters independently. The films presented in this thesis are deposited using a novel dual-plasma co-deposition approach in which the nanoparticles are produced separately in an upstream reactor and then injected into a secondary reactor where an amorphous silicon film is being grown. The degree of crystallinity and grain sizes of the films are evaluated using Raman spectroscopy and X-ray diffraction respectively. I describe detailed electronic measurements which reveal three distinct conduction mechanisms in n-type doped mixed-phase amorphous/nanocrystalline silicon thin films over a range of nanocrystallite concentrations and temperatures, covering the transition from fully amorphous to ~30% nanocrystalline. As the temperature is varied from 470 to 10 K, we observe activated conduction, multiphonon hopping (MPH) and Mott variable range hopping (VRH) as the nanocrystal content is increased. The transition from MPH to Mott-VRH hopping around 100K is ascribed to the freeze out of the phonon modes. A conduction model involving the parallel contributions of these three distinct conduction mechanisms is shown to describe both the conductivity and the reduced activation energy data to a high accuracy. Additional support is provided by measurements of thermal equilibration effects and noise spectroscopy, both done above room temperature (>300 K). This thesis provides a clear link between measurement and theory in these complex materials.

  8. Amorphous Polymeric Drug Salts as Ionic Solid Dispersion Forms of Ciprofloxacin.

    PubMed

    Mesallati, Hanah; Umerska, Anita; Paluch, Krzysztof J; Tajber, Lidia

    2017-07-03

    Ciprofloxacin (CIP) is a poorly soluble drug that also displays poor permeability. Attempts to improve the solubility of this drug to date have largely focused on the formation of crystalline salts and metal complexes. The aim of this study was to prepare amorphous solid dispersions (ASDs) by ball milling CIP with various polymers. Following examination of their solid state characteristics and physical stability, the solubility advantage of these ASDs was studied, and their permeability was investigated via parallel artificial membrane permeability assay (PAMPA). Finally, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the ASDs were compared to those of CIP. It was discovered that acidic polymers, such as Eudragit L100, Eudragit L100-55, Carbopol, and HPMCAS, were necessary for the amorphization of CIP. In each case, the positively charged secondary amine of CIP was found to interact with carboxylate groups in the polymers, forming amorphous polymeric drug salts. Although the ASDs began to crystallize within days under accelerated stability conditions, they remained fully X-ray amorphous following exposure to 90% RH at 25 °C, and demonstrated higher than predicted glass transition temperatures. The solubility of CIP in water and simulated intestinal fluid was also increased by all of the ASDs studied. Unlike a number of other solubility enhancing formulations, the ASDs did not decrease the permeability of the drug. Similarly, no decrease in antibiotic efficacy was observed, and significant improvements in the MIC and MBC of CIP were obtained with ASDs containing HPMCAS-LG and HPMCAS-MG. Therefore, ASDs may be a viable alternative for formulating CIP with improved solubility, bioavailability, and antimicrobial activity.

  9. Amorphous Ternary Diffusion Barriers for Silicon Metallizations

    NASA Astrophysics Data System (ADS)

    Reid, Jason Sven

    1995-01-01

    Reactively sputtered from transition-metal silicide or boride targets in Ar/N_2 discharges, thin amorphous films of TM-Si-N (TM = Mo, Ta, Ti, or W) and W-B-N are investigated. Resistivity, density, stress, and structure are given as functions of composition, and in some cases, temperature. Transmission electron microscopy shows that most of the films are marginally amorphous with the scale of local order ranging from 0.5 to 1.5 nm. Small -angle scattering measurements reveal chemically dissimilary regions in the films. When fully nitrided, Si appears to be preferentially bonded to nitrogen in the form of Si_3N_4 in the TM-Si-N films, according to extended energy loss fine structure (EXELFS) measurements. By tests on shallow-junction diodes, 100-nm thick TM-Si-N barriers are able to prevent aluminum overlayers from spiking the Si substrate at temperatures above aluminum's melting point, 660^circC. The exceptional stability is partly attributable to a 3 nm, self-sealing AlN layer which grows at the TM-Si-N/Al interface. The performance of the TM-Si-N and W-B-N barriers with copper overlayers is equally impressive. At the proper compositions, 100-nm barriers prevent copper from diffusing into the junction at 800^circC or higher for a 30-min vacuum annealing. Diode failure typically corresponds to the crystallization temperature of the barrier, which can be reduced by the presence of copper. Preliminary diffusion measurements of Cu in Ta _{36}Si_ {14}N_{50} films by SIMS yield an approximate diffusivity constant of D_{CU} = (0.014 cm ^2/s) times exp(-2.7 eV/kT). A 10-nm-thick TM-Si-N barrier with a Cu overlayer on MOS capacitors reveals no penetration of Cu into SiO_2 during an 80 h bias-thermal-stress at 300^circ C and 1 MV/cm applied field. Through a microscopic four-point probe lithographically defined on a Cu/barrier/Cu trilayer stack, the specific contact resistances of barrier/Cu interfaces are determined for TM-Si-N, TiN, and W barriers. In all instances, the

  10. Electrochemically synthesized amorphous and crystalline nanowires: dissimilar nanomechanical behavior in comparison with homologous flat films

    NASA Astrophysics Data System (ADS)

    Zeeshan, M. A.; Esqué-de Los Ojos, D.; Castro-Hartmann, P.; Guerrero, M.; Nogués, J.; Suriñach, S.; Baró, M. D.; Nelson, B. J.; Pané, S.; Pellicer, E.; Sort, J.

    2016-01-01

    The effects of constrained sample dimensions on the mechanical behavior of crystalline materials have been extensively investigated. However, there is no clear understanding of these effects in nano-sized amorphous samples. Herein, nanoindentation together with finite element simulations are used to compare the properties of crystalline and glassy CoNi(Re)P electrodeposited nanowires (φ ~ 100 nm) with films (3 μm thick) of analogous composition and structure. The results reveal that amorphous nanowires exhibit a larger hardness, lower Young's modulus and higher plasticity index than glassy films. Conversely, the very large hardness and higher Young's modulus of crystalline nanowires are accompanied by a decrease in plasticity with respect to the homologous crystalline films. Remarkably, proper interpretation of the mechanical properties of the nanowires requires taking the curved geometry of the indented surface and sink-in effects into account. These findings are of high relevance for optimizing the performance of new, mechanically-robust, nanoscale materials for increasingly complex miniaturized devices.The effects of constrained sample dimensions on the mechanical behavior of crystalline materials have been extensively investigated. However, there is no clear understanding of these effects in nano-sized amorphous samples. Herein, nanoindentation together with finite element simulations are used to compare the properties of crystalline and glassy CoNi(Re)P electrodeposited nanowires (φ ~ 100 nm) with films (3 μm thick) of analogous composition and structure. The results reveal that amorphous nanowires exhibit a larger hardness, lower Young's modulus and higher plasticity index than glassy films. Conversely, the very large hardness and higher Young's modulus of crystalline nanowires are accompanied by a decrease in plasticity with respect to the homologous crystalline films. Remarkably, proper interpretation of the mechanical properties of the nanowires

  11. Application of Laser Design of Amorphous Feco-Based Alloys for the Formation of Amorphous-Crystalline Composites

    NASA Astrophysics Data System (ADS)

    Permyakova, I. E.; Glezer, A. M.; Ivanov, A. A.; Shelyakov, A. V.

    2016-01-01

    Morphological and fractographic features of change of FeCo-based amorphous alloy surfaces after laser treatment are studied in detail. Regimes of laser treatment that allow various degrees of crystallization of the examined alloys to be obtained, including thin (<1 •m) crystal layers on amorphous alloy surfaces, amorphous-crystalline composites, and completely crystalline alloys are adjusted. The Vickers hardness is estimated in zones of selective laser irradiation. The structure of the examined alloys attendant to the change of their mechanical properties is analyzed.

  12. Evaluation of nuclear reaction cross section data for the production of (87)Y and (88)Y via proton, deuteron and alpha-particle induced transmutations.

    PubMed

    Zaneb, H; Hussain, M; Amjad, N; Qaim, S M

    2016-06-01

    Proton, deuteron and alpha-particle induced reactions on (87,88)Sr, (nat)Zr and (85)Rb targets were evaluated for the production of (87,88)Y. The literature data were compared with nuclear model calculations using the codes ALICE-IPPE, TALYS 1.6 and EMPIRE 3.2. The evaluated cross sections were generated; therefrom thick target yields of (87,88)Y were calculated. Analysis of radio-yttrium impurities and yield showed that the (87)Sr(p, n)(87)Y and (88)Sr(p, n)(88)Y reactions are the best routes for the production of (87)Y and (88)Y respectively. The calculated yield for the (87)Sr(p, n)(87)Y reaction is 104 MBq/μAh in the energy range of 14→2.7MeV. Similarly, the calculated yield for the (88)Sr(p, n)(88)Y reaction is 3.2 MBq/μAh in the energy range of 15→7MeV.

  13. Elemental and mineralogical study of earth-based pigments using particle induced X-ray emission and X-ray diffraction

    NASA Astrophysics Data System (ADS)

    Nel, P.; Lynch, P. A.; Laird, J. S.; Casey, H. M.; Goodall, L. J.; Ryan, C. G.; Sloggett, R. J.

    2010-07-01

    Artwork and precious artefacts demand non-destructive analytical methodologies for art authentication, attribution and provenance assessment. However, structural and chemical characterisation represents a challenging problem with existing analytical techniques. A recent authentication case based on an Australian Aboriginal artwork, indicate there is substantial benefit in the ability of particle induced X-ray emission (PIXE), coupled with dynamic analysis (DA) to characterise pigments through trace element analysis. However, this information alone is insufficient for characterising the mineralogical residence of trace elements. For this reason a combined methodology based on PIXE and X-ray diffraction (XRD) has been performed to explore the benefits of a more comprehensive data set. Many Aboriginal paintings and artefacts are predominantly earth pigment based. This makes these cultural heritage materials an ideal case study for testing the above combined methodological approach on earth-based pigments. Samples of synthetic and naturally occurring earth-based pigments were obtained from a range of sources, which include Indigenous communities within Australia's Kimberley region. PIXE analyses using a 3 MeV focussed proton beam at the CSIRO nuclear microprobe, as well as laboratory-based XRD was carried out on the above samples. Elemental signature spectra as well as mineralogical data were used to assess issues regarding synthetic and naturally occurring earth pigments with the ultimate aim of establishing provenance.

  14. Particle-induced X-ray emission analysis of elements in plasma from wild and captive sea turtles (Eretmochelys imbricata, Chelonia mydas, and Caretta caretta) in Okinawa, Japan.

    PubMed

    Suzuki, Kazuyuki; Noda, Jun; Yanagisawa, Makio; Kawazu, Isao; Sera, Kouichiro; Fukui, Daisuke; Asakawa, Mitsuhiko; Yokota, Hiroshi

    2012-09-01

    The aim of this study was to evaluate the reliability of direct determination of trace and major element concentrations in plasma samples from wild (six hawksbill, nine green, and nine loggerhead) and captive sea turtles (25 howksbill, five green, and three loggerhead) in Okinawa, Japan. The particle induced X-ray emission method allowed detection of 23 trace and major elements (Al, As, Br, Ca, Cl, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Ni, P, Pb, S, Se, Si, Sr, Ti, Y, and Zn). The wild sea turtles were found to have high concentrations of As and Pb in plasma compared with captive, but there were no significant changes in the Al and Hg concentrations. Loggerhead sea turtles were found to have significantly higher accumulation of As and Pb in plasma in comparison to other species. These findings may be useful when adjusting environmental and species-related factors in severely polluted marine ecosystems. Our results indicate that measuring the plasma As and Pb concentrations in wild sea turtles might be of help to assess the level of pollution in marine ecosystems, keeping in mind that loggerhead sea turtles had been shown to have higher levels of As and Pb in plasma.

  15. PIXE (particle induced X-ray emission): A non-destructive analysis method adapted to the thin decorative coatings of antique ceramics

    NASA Astrophysics Data System (ADS)

    Leon, Y.; Sciau, Ph.; Bouquillon, A.; Pichon, L.; de Parseval, Ph.

    2012-11-01

    Recent trends in study of Greek and Roman potteries have been to develop non-abrasive methods to determine the elemental composition of their thin coatings. This paper investigates the potential of PIXE (particle induced X-ray emission) in this field. This technique has been currently used to determine the bulk elemental composition of several types of artifacts because of its fast and simultaneous ability to measure a large number of elements with good accuracy and without any damage to the sample. However, until now it has never been applied to the measurement of the composition of thin layers owing to the difficulty in limiting the depth of analysis to the layer thickness. In this paper, we show, through a comparative study of reference clay pellets and thin coatings of Terra Sigillata ceramics that reducing the energy of the particle beam the problem can be solved. The decrease of proton energy from 3 MeV (standard condition) to 1.5 MeV allowed us to limit the analyzed depth to the coating thickness without significant alteration of the results. Quantitative elemental analysis remains possible and the quality of results is similar to the one obtained from electron microprobe.

  16. Development of particle induced gamma-ray emission methods for nondestructive determination of isotopic composition of boron and its total concentration in natural and enriched samples.

    PubMed

    Chhillar, Sumit; Acharya, Raghunath; Sodaye, Suparna; Pujari, Pradeep K

    2014-11-18

    We report simple particle induced gamma-ray emission (PIGE) methods using a 4 MeV proton beam for simultaneous and nondestructive determination of the isotopic composition of boron ((10)B/(11)B atom ratio) and total boron concentrations in various solid samples with natural isotopic composition and enriched with (10)B. It involves measurement of prompt gamma-rays at 429, 718, and 2125 keV from (10)B(p,αγ)(7)Be, (10)B(p, p'γ)(10)B, and (11)B(p, p'γ)(11)B reactions, respectively. The isotopic composition of boron in natural and enriched samples was determined by comparing peak area ratios corresponding to (10)B and (11)B of samples to natural boric acid standard. An in situ current normalized PIGE method, using F or Al, was standardized for total B concentration determination. The methods were validated by analyzing stoichiometric boron compounds and applied to samples such as boron carbide, boric acid, carborane, and borosilicate glass. Isotopic compositions of boron in the range of 0.247-2.0 corresponding to (10)B in the range of 19.8-67.0 atom % and total B concentrations in the range of 5-78 wt % were determined. It has been demonstrated that PIGE offers a simple and alternate method for total boron as well as isotopic composition determination in boron based solid samples, including neutron absorbers that are important in nuclear technology.

  17. First Quantitative Imaging of Organic Fluorine within Angiogenic Tissues by Particle Induced Gamma-Ray Emission (PIGE) Analysis: First PIGE Organic Fluorine Imaging

    PubMed Central

    Lavielle, Sébastien; Gionnet, Karine; Ortega, Richard; Devès, Guillaume; Kilarski, Victor; Wehbe, Katia; Bikfalvi, Andreas; Déléris, Gérard

    2011-01-01

    PET (Positron Emission Tomography) allows imaging of the in vivo distribution of biochemical compounds labeled with a radioactive tracer, mainly 18F-FDG (2-deoxy-2-[18F] fluoro-D-glucose). 18F only allows a relatively poor spatial resolution (2-3 mm) which does not allow imaging of small tumors or specific small size tissues, e.g. vasculature. Unfortunately, angiogenesis is a key process in various physiologic and pathologic processes and is, for instance, involved in modern anticancer approaches. Thus ability to visualize angiogenesis could allow early diagnosis and help to monitor the response of cancer to specific chemotherapies. Therefore, indirect analytical techniques are required to assess the localization of fluorinated compounds at a micrometric scale. Multimodality imaging approaches could provide accurate information on the metabolic activity of the target tissue. In this article, PIGE method (Particle Induced Gamma-ray Emission) was used to determine fluorinated tracers by the nuclear reaction of 19F(p,p′γ)19F in tissues. The feasibility of this approach was assessed on polyfluorinated model glucose compounds and novel peptide-based tracer designed for angiogenesis imaging. Our results describe the first mapping of the biodistribution of fluorinated compounds in both vascularized normal tissue and tumor tissue. PMID:24310427

  18. First Quantitative Imaging of Organic Fluorine within Angiogenic Tissues by Particle Induced Gamma-Ray Emission (PIGE) Analysis: First PIGE Organic Fluorine Imaging.

    PubMed

    Lavielle, Sébastien; Gionnet, Karine; Ortega, Richard; Devès, Guillaume; Kilarski, Victor; Wehbe, Katia; Bikfalvi, Andreas; Déléris, Gérard

    2011-03-09

    PET (Positron Emission Tomography) allows imaging of the in vivo distribution of biochemical compounds labeled with a radioactive tracer, mainly 18F-FDG (2-deoxy-2-[18F] fluoro-D-glucose). 18F only allows a relatively poor spatial resolution (2-3 mm) which does not allow imaging of small tumors or specific small size tissues, e.g. vasculature. Unfortunately, angiogenesis is a key process in various physiologic and pathologic processes and is, for instance, involved in modern anticancer approaches. Thus ability to visualize angiogenesis could allow early diagnosis and help to monitor the response of cancer to specific chemotherapies. Therefore, indirect analytical techniques are required to assess the localization of fluorinated compounds at a micrometric scale. Multimodality imaging approaches could provide accurate information on the metabolic activity of the target tissue. In this article, PIGE method (Particle Induced Gamma-ray Emission) was used to determine fluorinated tracers by the nuclear reaction of 19F(p,p'γ)19F in tissues. The feasibility of this approach was assessed on polyfluorinated model glucose compounds and novel peptide-based tracer designed for angiogenesis imaging. Our results describe the first mapping of the biodistribution of fluorinated compounds in both vascularized normal tissue and tumor tissue.

  19. Simultaneous determination of Si, Al and Na concentrations by particle induced gamma-ray emission and applications to reference materials and ceramic archaeological artifacts

    NASA Astrophysics Data System (ADS)

    Dasari, K. B.; Chhillar, S.; Acharya, R.; Ray, D. K.; Behera, A.; Lakshmana Das, N.; Pujari, P. K.

    2014-11-01

    A particle induced gamma ray emission (PIGE) method using 4 MeV proton beam was standardized for simultaneous determination of Si, Al and Na concentrations and has been applied for non-destructive analysis of several reference materials and archaeological clay pottery samples. Current normalized count rates of gamma-rays for the three elements listed above were obtained by an in situ method using Li as internal standard. The paper presents application of the in situ current normalized PIGE method for grouping study of 39 clay potteries, obtained from Rajasthan and Andhra Pradesh states of India. Grouping of artifacts was carried out using the ratios of SiO2 to Al2O3 concentrations, due to their non volatile nature. Powder samples and elemental standards in pellet forms (cellulose matrix) were irradiated using the 4 MeV proton beam (∼10 nA) from the 3 MV tandem accelerator at IOP Bhubaneswar, and assay of prompt gamma rays was carried out using a 60% relative efficiency HPGe detector coupled to MCA. The concentration ratio values of SiO2/Al2O3 indicated that pottery samples fell into two major groups, which are in good agreement with their collection areas. Reference materials from IAEA and NIST were analyzed for quantification of Si, Al and Na concentrations as a part of validation as well as application of PIGE method.

  20. Method of inducing differential etch rates in glow discharge produced amorphous silicon

    DOEpatents

    Staebler, David L.; Zanzucchi, Peter J.

    1980-01-01

    A method of inducing differential etch rates in glow discharge produced amorphous silicon by heating a portion of the glow discharge produced amorphous silicon to a temperature of about 365.degree. C. higher than the deposition temperature prior to etching. The etch rate of the exposed amorphous silicon is less than the unheated amorphous silicon.