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Sample records for chemically bonded phosphate

  1. Vitrified chemically bonded phosphate ceramics for immobilization of radioisotopes

    Science.gov (United States)

    Wagh, Arun S.

    2016-04-05

    A method of immobilizing a radioisotope and vitrified chemically bonded phosphate ceramic (CBPC) articles formed by the method are described. The method comprises combining a radioisotope-containing material, MgO, a source of phosphate, and optionally, a reducing agent, in water at a temperature of less than 100.degree. C. to form a slurry; curing the slurry to form a solid intermediate CBPC article comprising the radioisotope therefrom; comminuting the intermediate CBPC article, mixing the comminuted material with glass frits, and heating the mixture at a temperature in the range of about 900 to about 1500.degree. C. to form a vitrified CBPC article comprising the radioisotope immobilized therein.

  2. Method of waste stabilization with dewatered chemically bonded phosphate ceramics

    Science.gov (United States)

    Wagh, Arun; Maloney, Martin D.

    2010-06-29

    A method of stabilizing a waste in a chemically bonded phosphate ceramic (CBPC). The method consists of preparing a slurry including the waste, water, an oxide binder, and a phosphate binder. The slurry is then allowed to cure to a solid, hydrated CBPC matrix. Next, bound water within the solid, hydrated CBPC matrix is removed. Typically, the bound water is removed by applying heat to the cured CBPC matrix. Preferably, the quantity of heat applied to the cured CBPC matrix is sufficient to drive off water bound within the hydrated CBPC matrix, but not to volatalize other non-water components of the matrix, such as metals and radioactive components. Typically, a temperature range of between 100.degree. C.-200.degree. C. will be sufficient. In another embodiment of the invention wherein the waste and water have been mixed prior to the preparation of the slurry, a select amount of water may be evaporated from the waste and water mixture prior to preparation of the slurry. Another aspect of the invention is a direct anyhydrous CBPC fabrication method wherein water is removed from the slurry by heating and mixing the slurry while allowing the slurry to cure. Additional aspects of the invention are ceramic matrix waste forms prepared by the methods disclosed above.

  3. EVALUATION OF CHEMICALLY BONDED PHOSPHATE CERAMICS FOR MERCURY STABILIZATION OF A MIXED SYNTHETIC WASTE

    Science.gov (United States)

    This experimental study was conducted to evaluate the stabilization and encapsulation technique developed by Argonne National Laboratory, called the Chemically Bonded Phosphate Ceramics technology for Hg- and HgCl2-contaminated synthetic waste materials. Leachability ...

  4. Effective solidification/stabilisation of mercury-contaminated wastes using zeolites and chemically bonded phosphate ceramics.

    Science.gov (United States)

    Zhang, Shaoqing; Zhang, Xinyan; Xiong, Ya; Wang, Guoping; Zheng, Na

    2015-02-01

    In this study, two kinds of zeolites materials (natural zeolite and thiol-functionalised zeolite) were added to the chemically bonded phosphate ceramic processes to treat mercury-contaminated wastes. Strong promotion effects of zeolites (natural zeolite and thiol-functionalised zeolite) on the stability of mercury in the wastes were obtained and these technologies showed promising advantages toward the traditional Portland cement process, i.e. using Portland cement as a solidification agent and natural or thiol-functionalised zeolite as a stabilisation agent. Not only is a high stabilisation efficiency (lowered the Toxicity Characteristic Leaching Procedure Hg by above 10%) obtained, but also a lower dosage of solidification (for thiol-functionalised zeolite as stabilisation agent, 0.5 g g(-1) and 0.7 g g(-1) for chemically bonded phosphate ceramic and Portland cement, respectively) and stabilisation agents (for natural zeolite as stabilisation agent, 0.35 g g(-1) and 0.4 g g(-1) for chemically bonded phosphate ceramic and Portland cement, respectively) were used compared with the Portland cement process. Treated by thiol-functionalised zeolite and chemically bonded phosphate ceramic under optimum parameters, the waste containing 1500 mg Hg kg(-1) passed the Toxicity Characteristic Leaching Procedure test. Moreover, stabilisation/solidification technology using natural zeolite and chemically bonded phosphate ceramic also passed the Toxicity Characteristic Leaching Procedure test (the mercury waste containing 625 mg Hg kg(-1)). Moreover, the presence of chloride and phosphate did not have a negative effect on the chemically bonded phosphate ceramic/thiol-functionalised zeolite treatment process; thus, showing potential for future application in treatment of 'difficult-to-manage' mercury-contaminated wastes or landfill disposal with high phosphate and chloride content.

  5. Chemically bonded phosphate ceramics for radioactive and mixed waste solidification and stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Wagh, A.S.; Cunnane, J.C.; Singh, D.; Reed, D.T.; Armstrong, S.; Subhan, W.; Chawla, N.

    1993-01-01

    Results of an initial investigation of low temperature setting chemically bonded magnesium ammonium phosphate (MAP) ceramics as waste form materials, for solidification and stabilization of radioactive and mixed waste, are reported. The suitability of MAP for solidifying and encapsulating waste materials was tested by encapsulating zeolites at loadings up to [approximately]50 wt%. The resulting composites exhibited very good compressive strength characteristics. Microstructure studies show that zeolite grains remain unreacted in the matrix. Potential uses for solidifying and stab wastes are discussed.

  6. Chemically bonded phosphate ceramics for radioactive and mixed waste solidification and stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Wagh, A.S.; Cunnane, J.C.; Singh, D.; Reed, D.T.; Armstrong, S.; Subhan, W.; Chawla, N.

    1993-01-01

    Results of an initial investigation of low temperature setting chemically bonded magnesium ammonium phosphate (MAP) ceramics as waste form materials, for solidification and stabilization of radioactive and mixed waste, are reported. The suitability of MAP for solidifying and encapsulating waste materials was tested by encapsulating zeolites at loadings up to {approximately}50 wt%. The resulting composites exhibited very good compressive strength characteristics. Microstructure studies show that zeolite grains remain unreacted in the matrix. Potential uses for solidifying and stab wastes are discussed.

  7. Effect of raw material ratios on the compressive strength of magnesium potassium phosphate chemically bonded ceramics.

    Science.gov (United States)

    Wang, Ai-juan; Yuan, Zhi-long; Zhang, Jiao; Liu, Lin-tao; Li, Jun-ming; Liu, Zheng

    2013-12-01

    The compressive strength of magnesium potassium phosphate chemically bonded ceramics is important in biomedical field. In this work, the compressive strength of magnesium potassium phosphate chemically bonded ceramics was investigated with different liquid-to-solid and MgO-to-KH2PO4 ratios. X-ray diffractometer was applied to characterize its phase composition. The microstructure was imaged using a scanning electron microscope. The results showed that the compressive strength of the chemically bonded ceramics increased with the decrease of liquid-to-solid ratio due to the change of the packing density and the crystallinity of hydrated product. However, with the increase of MgO-to-KH2PO4 weight ratio, its compressive strength increased firstly and then decreased. The low compressive strength in lower MgO-to-KH2PO4 ratio might be explained by the existence of the weak phase KH2PO4. However, the low value of compressive strength with the higher MgO-to-KH2PO4 ratio might be caused by lack of the joined phase in the hydrated product. Besides, it has been found that the microstructures were different in these two cases by the scanning electron microscope. Colloidal structure appeared for the samples with lower liquid-to-solid and higher MgO-to-KH2PO4 ratios possibly because of the existence of amorphous hydrated products. The optimization of both liquid-to-solid and MgO-to-KH2PO4 ratios was important to improve the compressive strength of magnesium potassium phosphate chemically bonded ceramics.

  8. Processing–structure–property relations of chemically bonded phosphate ceramic composites

    Indian Academy of Sciences (India)

    H A Colorado; C Hiel; H T Hahn

    2011-07-01

    Mechanical properties and microstructures of a chemically bonded phosphate ceramic (CBPC) and its composite with 1.0 wt% graphite nanoplatelets (GNPs) reinforcement have been investigated. Microstructure was identified by using optical and scanning electron microscopes, X-ray tomography, and X-ray diffraction. In addition, weight loss of the resin at room temperature was studied. The microstructure characterization shows that CBPC is itself a composite with several crystalline (wollastonite and brushite) and amorphous phases. SEM and micro tomography show a homogeneous distribution of crystalline phases. Bending and compression strength of the CBPC was improved by reducing bubbles via preparation in vacuum.

  9. Novel Chemically-Bonded Phosphate Ceramic Borehole Sealants (Ceramicretes) for Arctic Environments

    Energy Technology Data Exchange (ETDEWEB)

    Shirish Patil; Godwin A. Chukwu; Gang Chen; Santanu Khataniar

    2008-12-31

    Novel chemically bonded phosphate ceramic borehole sealant, i.e. Ceramicrete, has many advantages over conventionally used permafrost cement at Alaska North Slope (ANS). However, in normal field practices when Ceramicrete is mixed with water in blenders, it has a chance of being contaminated with leftover Portland cement. In order to identify the effect of Portland cement contamination, recent tests have been conducted at BJ services in Tomball, TX as well as at the University of Alaska Fairbanks with Ceramicrete formulations proposed by the Argonne National Laboratory. The tests conducted at BJ Services with proposed Ceramicrete formulations and Portland cement contamination have shown significant drawbacks which has caused these formulations to be rejected. However, the newly developed Ceramicrete formulation at the University of Alaska Fairbanks has shown positive results with Portland cement contamination as well as without Portland cement contamination for its effective use in oil well cementing operations at ANS.

  10. Wollastonite based-Chemically Bonded Phosphate Ceramics with lead oxide contents under gamma irradiation

    Science.gov (United States)

    Colorado, H. A.; Pleitt, J.; Hiel, C.; Yang, J. M.; Hahn, H. T.; Castano, C. H.

    2012-06-01

    The shielding properties to gamma rays as well as the effect of lead concentration incorporated into Chemically Bonded Phosphate Ceramics (CBPCs) composites are presented. The Wollastonite-based CBPC was fabricated by mixing a patented aqueous phosphoric acid formulation with Wollastonite powder. CBPC has been proved to be good structural material, with excellent thermal resistant properties, and research already showed their potential for radiation shielding applications. Wollastonite-based CBPC is a composite material itself with several crystalline and amorphous phases. Irradiation experiments were conducted on different Wollastonite-based CBPCs with lead oxide. Radiation shielding potential, attenuation coefficients in a broad range of energies pertinent to engineering applications and density experiments showing the effect of the PbO additions (to improve gamma shielding capabilities) are also presented. Microstructure was identified by using scanning electron microscopy and X-ray diffraction.

  11. Stabilization of Rocky Flats Pu-contaminated ash within chemically bonded phosphate ceramics

    Science.gov (United States)

    Wagh, A. S.; Strain, R.; Jeong, S. Y.; Reed, D.; Krause, T.; Singh, D.

    A feasibility study was conducted on the use of chemically bonded phosphate ceramics for stabilization of combustion residue of high transuranic (TRU) wastes. Using a matrix of magnesium potassium phosphate formed by the room-temperature reaction of MgO and KH 2PO 4 solution, we made waste forms that contained 5 wt% Pu to satisfy the requirements of the Waste Isolation Pilot Plant. The waste forms were ceramics whose compression strength was twice that of conventional cement grout and whose connected porosity was ≈50% that of cement grout. Both surrogate and actual waste forms displayed high leaching resistance for both hazardous metals and Pu. Hydrogen generation resulting from the radiolytic decomposition of water and organic compounds present in the waste form did not appear to be a significant issue. Pu was present as PuO 2 that was physically microencapsulated in the matrix. In the process, pyrophoricity was removed and leaching resistance was enhanced. The high leaching resistance was due to the very low solubility of PuO 2 coupled with superior microencapsulation. As a result, the waste forms satisfied the current Safeguard Termination Limit requirement for storage of TRU combustion residues.

  12. Critical surface energy of composite cement containing MDP (10-methacryloyloxydecyl dihydrogen phosphate) and chemical bonding to hydroxyapatite.

    Science.gov (United States)

    Dabsie, Firas; Grégoire, Geneviève; Sharrock, Patrick

    2012-01-01

    Self-adhesive composite cements are increasingly used for cementing inlays/onlays, intraradicular posts, crowns and laminate veneers. Wider clinical acceptance is driven by simpler and faster handling procedures, much like observed for self-etching adhesives. 10-Methacryloyloxydecyl dihydrogen phosphate (MDP) is a bi-functional monomer incorporated as the reactive ingredient in a contemporary self-adhesive cement. We have examined the surface free energy parameters of this cement and studied the mode of action of the cement on dentine substrate by contact angle measurements to determine the critical surface energy of the cement. Retention of the infrared absorption bands characteristic of the acrylate moieties on the surface of hydroxyapatite particles suggests that MDP contributes to the overall bonding to dentine by forming ionic chemical bonds with surface calcium ions in dentine crystalites.

  13. Chemical bond fundamental aspects of chemical bonding

    CERN Document Server

    Frenking, Gernot

    2014-01-01

    This is the perfect complement to ""Chemical Bonding - Across the Periodic Table"" by the same editors, who are two of the top scientists working on this topic, each with extensive experience and important connections within the community. The resulting book is a unique overview of the different approaches used for describing a chemical bond, including molecular-orbital based, valence-bond based, ELF, AIM and density-functional based methods. It takes into account the many developments that have taken place in the field over the past few decades due to the rapid advances in quantum chemica

  14. Hydrogen Bonding in Phosphine Oxide/Phosphate-Phenol Complexes

    NARCIS (Netherlands)

    Cuypers, R.; Sudhölter, E.J.R.; Zuilhof, H.

    2010-01-01

    To develop a new solvent-impregnated resin (SIR) system for the removal of phenols and thiophenols from water, complex formation by hydrogen bonding of phosphine oxides and phosphates is studied using isothermal titration calorimetry (ITC) and quantum chemical modeling. Six different computational m

  15. Improvement of ground granulated blast furnace slag on stabilization/solidification of simulated mercury-doped wastes in chemically bonded phosphate ceramics.

    Science.gov (United States)

    Liu, Zhongzhe; Qian, Guangren; Zhou, Jizhi; Li, Chuanhua; Xu, Yunfeng; Qin, Zhe

    2008-08-30

    This paper investigated the effectiveness of (ground granulated blast furnace slag) GGBFS-added chemically bonded phosphate ceramic (CBPC) matrix on the stabilization/solidification (S/S) of mercury chloride and simulated mercury-bearing light bulbs (SMLB). The results showed that the maximal compressive strength was achieved when 15% and 10% ground GGBFS was added for HgCl(2)-doped and SMLB-doped CBPC matrices, respectively. The S/S performances of GGBFS-added matrices were significantly better than non-additive matrices. As pore size was reduced, the leaching concentration of Hg(2+) from GGBFS-added CBPC matrix could be reduced from 697 microg/L to about 3 microg/L when treating HgCl(2). Meanwhile, the main hydrating product of GGBFS-added matrices was still MgKPO(4).6H(2)O. The improvement of S/S effectiveness was mainly due to physical filling of fine GGBFS particles and microencapsulation of chemical cementing gel.

  16. Dipentaerythritol penta-acrylate phosphate - an alternative phosphate ester monomer for bonding of methacrylates to zirconia

    Science.gov (United States)

    Chen, Ying; Tay, Franklin R.; Lu, Zhicen; Chen, Chen; Qian, Mengke; Zhang, Huaiqin; Tian, Fucong; Xie, Haifeng

    2016-12-01

    The present work examined the effects of dipentaerythritol penta-acrylate phosphate (PENTA) as an alternative phosphate ester monomer for bonding of methacrylate-based resins to yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) and further investigated the potential bonding mechanism involved. Shear bond strength testing was performed to evaluate the efficacy of experimental PENTA-containing primers (5, 10, 15, 20 or 30 wt% PENTA in acetone) in improving resin-Y-TZP bond strength. Bonding without the use of a PENTA-containing served as the negative control, and a Methacryloyloxidecyl dihydrogenphosphate(MDP)-containing primer was used as the positive control. Inductively coupled plasma-mass spectrometry (ICP-MS), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) were used to investigate the potential existence of chemical affinity between PENTA and Y-TZP. Shear bond strengths were significant higher in the 15 and 20 wt% PENTA groups. The ICP-MS, XPS and FTIR data indicated that the P content on the Y-TZP surface increased as the concentration of PENTA increased in the experimental primers, via the formation of Zr–O–P bond. Taken together, the results attest that PENTA improves resin bonding of Y-TZP through chemical reaction with Y-TZP. Increasing the concentration of PENTA augments its binding affinity but not its bonding efficacy with zirconia.

  17. Surface smoothness and marginal fit with phosphate-bonded investments.

    Science.gov (United States)

    Cooney, J P; Doyle, T M; Caputo, A A

    1979-04-01

    Two phosphate-bonded investments and one calcium sulfate investment were evaluated for the surface smoothness and marginal fit they impart to gold castings. A modified technique was also evaluated for each phosphate-bonded investment, where the silica sol was not diluted and the spatulation time was reduced. The results of this study lead to the following conclusions: 1. The marginal fits obtained with all four phosphate-bonded methods were comparable to each other and superior to that obtained with the calcium sulfate investment. 2. The presence of nodules on the surface of the castings was more prevalent with the phosphate-bonded investments. However, this effect was not statistically significant. 3. Clinical assessment of the roughness of the castings revealed that all the methods tested produced clinically acceptable castings. 4. Visual observation by five dentists revealed that both the recommended and modified techniques for one of the phosphate-bonded investments (Ceramigold) produced a smoother surface than any other investment tested. Rating of scanning electron microscope photographs (X600) revealed no difference in the surface roughness between any of the castings. Consequently, no definitive relation between investment type or technique and surface roughness was established. 5. No correlation was demonstrated between surface roughness, as evaluated by either clinical observation or scanning electron microscope photography, and marginal fit of the castings.

  18. Density Functionals of Chemical Bonding

    Directory of Open Access Journals (Sweden)

    Mihai V. Putz

    2008-06-01

    Full Text Available The behavior of electrons in general many-electronic systems throughout the density functionals of energy is reviewed. The basic physico-chemical concepts of density functional theory are employed to highlight the energy role in chemical structure while its extended influence in electronic localization function helps in chemical bonding understanding. In this context the energy functionals accompanied by electronic localization functions may provide a comprehensive description of the global-local levels electronic structures in general and of chemical bonds in special. Becke-Edgecombe and author’s Markovian electronic localization functions are discussed at atomic, molecular and solid state levels. Then, the analytical survey of the main workable kinetic, exchange, and correlation density functionals within local and gradient density approximations is undertaken. The hierarchy of various energy functionals is formulated by employing both the parabolic and statistical correlation degree of them with the electronegativity and chemical hardness indices by means of quantitative structure-property relationship (QSPR analysis for basic atomic and molecular systems.

  19. Valence-Bond Theory and Chemical Structure.

    Science.gov (United States)

    Klein, Douglas J.; Trinajstic, Nenad

    1990-01-01

    Discussed is the importance of valence bond theory on the quantum-mechanical theory of chemical structure and the nature of the chemical bond. Described briefly are early VB theory, development of VB theory, modern versions, solid-state applications, models, treatment in textbooks, and flaws in criticisms of valence bond theory. (KR)

  20. The chemical bond in inorganic chemistry the bond valence model

    CERN Document Server

    Brown, I David

    2016-01-01

    The bond valence model is a version of the ionic model in which the chemical constraints are expressed in terms of localized chemical bonds formed by the valence charge of the atoms. Theorems derived from the properties of the electrostatic flux predict the rules obeyed by both ionic and covalent bonds. They make quantitative predictions of coordination number, crystal structure, bond lengths and bond angles. Bond stability depends on the matching of the bonding strengths of the atoms, while the conflicting requirements of chemistry and space lead to the structural instabilities responsible for the unusual physical properties displayed by some materials. The model has applications in many fields ranging from mineralogy to molecular biology.

  1. Coulombic Models in Chemical Bonding.

    Science.gov (United States)

    Sacks, Lawrence J.

    1986-01-01

    Compares the coulumbic point charge model for hydrogen chloride with the valence bond model. It is not possible to assign either a nonpolar or ionic canonical form of the valence bond model, while the covalent-ionic bond distribution does conform to the point charge model. (JM)

  2. Graphene composites containing chemically bonded metal oxides

    Indian Academy of Sciences (India)

    K Pramoda; S Suresh; H S S Ramakrishna Matte; A Govindaraj

    2013-08-01

    Composites of graphene involving chemically bonded nano films of metal oxides have been prepared by reacting graphene containing surface oxygen functionalities with metal halide vapours followed by exposure to water vapour. The composites have been characterized by electron microscopy, atomic force microscopy and other techniques. Magnetite particles chemically bonded to graphene dispersible in various solvents have been prepared and they exhibit fairly high magnetization.

  3. Antimicrobial properties and dentin bonding strength of magnesium phosphate cements.

    Science.gov (United States)

    Mestres, G; Abdolhosseini, M; Bowles, W; Huang, S-H; Aparicio, C; Gorr, S-U; Ginebra, M-P

    2013-09-01

    The main objective of this work was to assess the antimicrobial properties and the dentin-bonding strength of novel magnesium phosphate cements (MPC). Three formulations of MPC, consisting of magnesium oxide and a phosphate salt, NH4H2PO4, NaH2PO4 or a mixture of both, were evaluated. As a result of the setting reaction, MPC transformed into either struvite (MgNH4PO4·6H2O) when NH4H2PO4 was used or an amorphous magnesium sodium phosphate when NaH2PO4 was used. The MPC had appropriate setting times for hard tissue applications, high early compressive strengths and higher strength of bonding to dentin than commercial mineral trioxide aggregate cement. Bacteriological studies were performed with fresh and aged cements against three bacterial strains, Escherichia coli, Pseudomonas aeruginosa (planktonic and in biofilm) and Aggregatibacter actinomycetemcomitans. These bacteria have been associated with infected implants, as well as other frequent hard tissue related infections. Extracts of different compositions of MPC had bactericidal or bacteriostatic properties against the three bacterial strains tested. This was associated mainly with a synergistic effect between the high osmolarity and alkaline pH of the MPC. These intrinsic antimicrobial properties make MPC preferential candidates for applications in dentistry, such as root fillers, pulp capping agents and cavity liners.

  4. Crystallo-chemical analyses of calcium phosphates

    Energy Technology Data Exchange (ETDEWEB)

    Sakae, Toshiro; Hayakawa, Tohru; Maruyama, Fumiaki; Nemoto, Kimiya; Kozawa, Yukishige [Nihon Univ., Matsudo, Chiba (Japan). School of Dentistry

    1997-12-01

    Several analytical techniques, methodology and their practical data processing were briefly described to investigate the crystallographic properties of calcium phosphates which are encountered in the field of dental sciences. The applied analytical techniques were X-ray fluorescence spectrometry (XFS), energy dispersive spectrometry (EDS), Fourier transform infrared spectrometry (FT-IR) and X-ray diffraction (XRD). The used materials were tetracalcium phosphate, hydroxyapatite, fluorapatite, {alpha}-tricalcium phosphate, {beta}-tricalcium phosphate, octacalcium phosphate, monetite, brushite and monocalcium phosphate monohydrate. (author)

  5. The correlation theory of the chemical bond

    CERN Document Server

    Szalay, Szilárd; Szilvási, Tibor; Veis, Libor; Legeza, Örs

    2016-01-01

    The notion of chemical bond is a very useful concept in chemistry. It originated at the beginning of chemistry, it is expressive for the classically thinking mind, and the errors arising from the approximative nature of the concept can often be ignored. In the first half of the twentieth century, however, we learned that the proper description of the microworld is given by quantum mechanics. Quantum mechanics gives more accurate results for chemical systems than any preceding model, however, it is very inexpressive for the classically thinking mind. The quantum mechanical description of the chemical bond is given in terms of delocalized bonding orbitals, or, alternatively, in terms of correlations of occupations of localized orbitals. However, in the latter case, multiorbital correlations were treated only in terms of two-orbital correlations, although the structure of multiorbital correlations is far richer; and, in the case of bonds established by more than two electrons, multiorbital correlations represent...

  6. The chemical bond of stibium. Technological aspects

    Directory of Open Access Journals (Sweden)

    Ashcheulov A. A.

    2011-08-01

    Full Text Available Thin structure of the chemical bond of the hexagonal and rhombohedral modifications of stibium was investigated. The boundaries of their polymorphism were identified, which opens new technological possibilities of creating optical, photoelectric, thermoelectric, and other materials for electronic equipment components.

  7. Phosphate-bonded glass cements for geothermal wells. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Rockett, T.J.

    1979-09-01

    Calcium aluminosilicate glasses were found to react with phosphoric acid in three ways depending upon silica content. Above 55% SiO/sub 2/ they are insoluble while below 50% they dissolve readily. The transition compositions release calcium and aluminum ions and a silica gel phase replaces the glass. Activation energies in the order of 10 kcal/mole are associated with the dissolution. Equilibrium studies in the systems CaO-P/sub 2/O/sub 5/-H/sub 2/O, Al/sub 2/O/sub 3/-P/sub 2/O/sub 5/-H/sub 2/O, and CaO-Al/sub 2/O/sub 3/-P/sub 2/O/sub 5/-H/sub 2/O were made to determine the phases which are stable at 200/sup 0/C in excess water. The CaO system shows hydroxylapatite, monetite and monocalcium orthophosphate are the stable phases. The Al/sub 2/O/sub 3/ system contains augelite, berlinite, and a high phosphate aluminum hydrate. The quaternary system shows the above phase plus a lime alumina hydrogarnet and crandallite. Cement made from a glass frit of the composition 45% SiO/sub 2/: 24% CaO: 24% Al/sub 2/O/sub 3/ has a compressive strength of 500 psi after several days in steam at 200/sup 0/C and 800 psi after months in steam. Bonding of cements to mild steel are discussed.

  8. The chemical bond structure and dynamics

    CERN Document Server

    Zewail, Ahmed

    1992-01-01

    This inspired book by some of the most influential scientists of our time--including six Nobel laureates--chronicles our emerging understanding of the chemical bond through the last nine decades and into the future. From Pauling's early structural work using x-ray and electron diffraction to Zewail's femtosecond lasers that probe molecular dynamics in real time; from Crick's molecular biology to Rich's molecular recognition, this book explores a rich tradition of scientific heritage and accomplishment. The perspectives given by Pauling, Perutz, Rich, Crick, Porter, Polanyi, Herschbach, Zewail,

  9. Effect of fluoride in phosphate buffer solution on bonding to artificially carious enamel.

    Science.gov (United States)

    Wang, Hao; Shimada, Yasushi; Tagami, Junji

    2007-09-01

    The purpose of the present study was to evaluate the effect of fluoride on resin bonding to artificially carious enamel. Specimens from demineralized human enamel sections were prepared using two commercially available adhesives (Clearfil SE Bond, Kuraray; Single Bond, 3M) and a composite resin (Clearfil AP-X, Kuraray) according to manufacturers' instructions. They were then immersed in phosphate buffered saline solution with varied fluoride concentrations at 0, 0.1, 0.5, 1, and 10 ppm. After immersion in each solution for one, three, or seven days, microshear bond strength was measured. The bond strengths of both adhesive systems to artificially carious enamel significantly increased after immersion in fluoride-phosphate buffer solution. Based on the findings obtained, we thus proposed not to remove the white enamel lesions for bonding in the clinic. They might be preserved and treated using fluoride applications.

  10. A Corpuscular Picture of Electrons in Chemical Bond

    CERN Document Server

    Ando, Koji

    2015-01-01

    We introduce a theory of chemical bond with a corpuscular picture of electrons. It employs a minimal set of localized electron wave packets with 'floating and breathing' degrees of freedom and the spin-coupling of non-orthogonal valence-bond theory. It accurately describes chemical bonds in ground and excited states of spin singlet and triplet, in a distinct manner from conventional theories, indicating potential for establishing a dynamical theory of electrons in chemical bonds.

  11. Characterization of iron-phosphate-silicate chemical garden structures.

    Science.gov (United States)

    Barge, Laura M; Doloboff, Ivria J; White, Lauren M; Stucky, Galen D; Russell, Michael J; Kanik, Isik

    2012-02-28

    Chemical gardens form when ferrous chloride hydrate seed crystals are added or concentrated solutions are injected into solutions of sodium silicate and potassium phosphate. Various precipitation morphologies are observed depending on silicate and phosphate concentrations, including hollow plumes, bulbs, and tubes. The growth of precipitates is controlled by the internal osmotic pressure, fluid buoyancy, and membrane strength. Additionally, rapid bubble-led growth is observed when silicate concentrations are high. ESEM/EDX analysis confirms compositional gradients within the membranes, and voltage measurements across the membranes during growth show a final potential of around 150-200 mV, indicating that electrochemical gradients are maintained across the membranes as growth proceeds. The characterization of chemical gardens formed with iron, silicate, and phosphate, three important components of an early earth prebiotic hydrothermal system, can help us understand the properties of analogous structures that likely formed at submarine alkaline hydrothermal vents in the Hadean-structures offering themselves as the hatchery of life.

  12. Calcium phosphate bioceramics prepared from wet chemically precipitated powders

    Directory of Open Access Journals (Sweden)

    Kristine Salma

    2010-03-01

    Full Text Available In this work calcium phosphates were synthesized by modified wet chemical precipitation route. Contrary to the conventional chemical precipitation route calcium hydroxide was homogenized with planetary mill. Milling calcium oxide and water in planetary ball mill as a first step of synthesis provides a highly dispersed calcium hydroxide suspension. The aim of this work was to study the influence of main processing parameters of wet chemical precipitation synthesis product and to control the morphology, phase and functional group composition and, consequently, thermal stability and microstructure of calcium phosphate bioceramics after thermal treatment. The results showed that it is possible to obtain calcium phosphates with different and reproducible phase compositions after thermal processing (hydroxyapatite [HAp], β-tricalcium phosphate [β-TCP] and HAp/β-TCP by modified wet-chemical precipitation route. The β-TCP phase content in sintered bioceramics samples is found to be highly dependent on the changes in technological parameters and it can be controlled with ending pH, synthesis temperature and thermal treatment. Pure, crystalline and highly thermally stable (up to 1300°C HAp bioceramics with homogenous grainy microstructure, grain size up to 200–250 nm and high open porosity can be successfully obtained by powder synthesized at elevated synthesis temperature of 70°C and stabilizing ending pH at 9.

  13. Upper Secondary Teachers' Knowledge for Teaching Chemical Bonding Models

    Science.gov (United States)

    Bergqvist, Anna; Drechsler, Michal; Chang Rundgren, Shu-Nu

    2016-01-01

    Researchers have shown a growing interest in science teachers' professional knowledge in recent decades. The article focuses on how chemistry teachers impart chemical bonding, one of the most important topics covered in upper secondary school chemistry courses. Chemical bonding is primarily taught using models, which are key for understanding…

  14. Porosity prediction of calcium phosphate cements based on chemical composition.

    Science.gov (United States)

    Öhman, Caroline; Unosson, Johanna; Carlsson, Elin; Ginebra, Maria Pau; Persson, Cecilia; Engqvist, Håkan

    2015-07-01

    The porosity of calcium phosphate cements has an impact on several important parameters, such as strength, resorbability and bioactivity. A model to predict the porosity for biomedical cements would hence be a useful tool. At the moment such a model only exists for Portland cements. The aim of this study was to develop and validate a first porosity prediction model for calcium phosphate cements. On the basis of chemical reaction, molar weight and density of components, a volume-based model was developed and validated using calcium phosphate cement as model material. 60 mol% β-tricalcium phosphate and 40 mol% monocalcium phosphate monohydrate were mixed with deionized water, at different liquid-to-powder ratios. Samples were set for 24 h at 37°C and 100% relative humidity. Thereafter, samples were dried either under vacuum at room temperature for 24 h or in air at 37 °C for 7 days. Porosity and phase composition were determined. It was found that the two drying protocols led to the formation of brushite and monetite, respectively. The model was found to predict well the experimental values and also data reported in the literature for apatite cements, as deduced from the small absolute average residual errors (brushite, monetite and apatite cements. The model gives a good estimate of the final porosity and has the potential to be used as a porosity prediction tool in the biomedical cement field.

  15. Biologically Analogous Calcium Phosphate Tubes from a Chemical Garden.

    Science.gov (United States)

    Hughes, Erik A B; Williams, Richard L; Cox, Sophie C; Grover, Liam M

    2017-02-28

    Calcium phosphate (CaPO4) tubes with features comparable to mineralized biological microstructures, such as Haversian canals, were grown from a calcium gel/phosphate solution chemical garden system. A significant difference in gel mass in response to high and low solute phosphate equivalent environments existed within 30 min of solution layering upon gel (p = 0.0067), suggesting that the nature of advective movement between gel and solution is dependent on the solution concentration. The transport of calcium cations (Ca(2+)) and phosphate anions (PO4(3-)) was quantified and changes in pH were monitored to explain the preferential formation of tubes within a PO4(3-) concentration range of 0.5-1.25 M. Ingress from the anionic solution phase into the gel followed by the liberation of Ca(2+) ions from the gel was found to be essential for acquiring self-assembled tubular CaPO4 structures. Tube analysis by scanning electron microscopy (SEM), X-ray diffraction (XRD), and micro X-ray florescence (μ-XRF) revealed hydroxyapatite (HA, Ca10(PO4)6(OH)2) and dicalcium phosphate dihydrate (DCPD, CaHPO4·2H2O) phases organized in a hierarchical manner. Notably, the tubule diameters ranged from 100 to 150 μm, an ideal size for the permeation of vasculature in biological hard tissue.

  16. Characterization of hydroxyphenol-terminated alkanethiol self-assembled monolayers: interactions with phosphates by chemical force spectrometry.

    Science.gov (United States)

    Azmi, Alyza A; Ebralidze, Iraklii I; Dickson, Steven E; Horton, J Hugh

    2013-03-01

    Tannins and humic substances, commonly referred to as natural organic matter (NOM), constitute an important component of natural water and soil systems. These species contain numerous hydroxyl and carboxyl functional groups whose reactivity is strongly dependent on both the quantity and location of these moieties on the aromatic ring. In the present study, self-assembled monolayers (SAMs) of 4-(12-mercaptododecyl)benzene-1,2-diol (o-hydroxyphenol-terminated); 5-(12-mercaptododecyl)benzene-1,3-diol (m-hydroxyphenol-terminated); bis(11-thioundecyl) hydrogen phosphate (monoprotic phosphate); and 11-thioundecyl dihydrogen phosphate (diprotic phosphate) were prepared and characterized using X-ray photoelectron spectroscopy (XPS), attenuated total reflectance infrared spectroscopy (ATR-IR), and water contact angle measurements. The interactions between phenolic groups with phosphates were examined as a function of pH using the chemical force spectrometry (CFS) technique. The observations are discussed in the context of hydrogen bonding and electrostatic repulsion interaction between corresponding species. Adhesion force profiles of hydroxyphenol isomers interacting with monoprotic phosphate are dominated by ionic H-bonding; however the strength of o-hydroxyphenol interactions is significantly higher. The difference in location of hydroxyl groups on the interface also results in significantly different force-distance profiles for the isomeric hydroxyphenols when interacting with diprotic phosphate.

  17. Gradient Bundle Analysis: A Full Topological Approach to Chemical Bonding

    CERN Document Server

    Morgenstern, Amanda

    2016-01-01

    The "chemical bond" is a central concept in molecular sciences, but there is no consensus as to what a bond actually is. Therefore, a variety of bonding models have been developed, each defining the structure of molecules in a different manner with the goal of explaining and predicting chemical properties. This thesis describes the initial development of gradient bundle analysis (GBA), a chemical bonding model that creates a high resolution picture of chemical interactions within the charge density framework. GBA is based on concepts from the quantum theory of atoms in molecules (QTAIM), but uses a more complete picture of the topology and geometry of the electron charge density to understand and predict bonding interactions. Gradient bundles are defined as volumes bounded by zero-flux surfaces (ZFSs) in the gradient of the charge density with well-defined energies. The structure of gradient bundles provides an avenue for detecting the locations of valence electrons, which correspond to reactive regions in a ...

  18. Closing in on chemical bonds by opening up relativity theory.

    Science.gov (United States)

    Whitney, Cynthia K

    2008-03-01

    This paper develops a connection between the phenomenology of chemical bonding and the theory of relativity. Empirical correlations between electron numbers in atoms and chemical bond stabilities in molecules are first reviewed and extended. Quantitative chemical bond strengths are then related to ionization potentials in elements. Striking patterns in ionization potentials are revealed when the data are viewed in an element-independent way, where element-specific details are removed via an appropriate scaling law. The scale factor involved is not explained by quantum mechanics; it is revealed only when one goes back further, to the development of Einstein's special relativity theory.

  19. Secondary waste form testing : ceramicrete phosphate bonded ceramics.

    Energy Technology Data Exchange (ETDEWEB)

    Singh, D.; Ganga, R.; Gaviria, J.; Yusufoglu, Y. (Nuclear Engineering Division); ( ES)

    2011-06-21

    binder components from the waste form surface. Waste forms for ANS 16.1 leach testing contained appropriate amounts of rhenium and iodine as radionuclide surrogates, along with the additives silver-loaded zeolite and tin chloride. The leachability index for Re was found to range from 7.9 to 9.0 for all the samples evaluated. Iodine was below detection limit (5 ppb) for all the leachate samples. Further, leaching of sodium was low, as indicated by the leachability index ranging from 7.6-10.4, indicative of chemical binding of the various chemical species. Target leachability indices for Re, I, and Na were 9, 11, and 6, respectively. Degradation was observed in some of the samples post 90-day ANS 16.1 tests. Toxicity characteristic leaching procedure (TCLP) results showed that all the hazardous contaminants were contained in the waste, and the hazardous metal concentrations were below the Universal Treatment Standard limits. Preliminary scale-up (2-gal waste forms) was conducted to demonstrate the scalability of the Ceramicrete process. Use of minimal amounts of boric acid as a set retarder was used to control the working time for the slurry. Flexibility in treating waste streams with wide ranging compositional make-ups and ease of process scale-up are attractive attributes of Ceramicrete technology.

  20. Radiological and chemical assessment of phosphate rocks in some countries

    Energy Technology Data Exchange (ETDEWEB)

    Cevik, U., E-mail: ugurc@ktu.edu.tr [Karadeniz Technical University, Department of Physics, Trabzon (Turkey); Baltas, H. [Rize University, Department of Physics, Rize (Turkey); Tabak, A. [Rize University, Department of Chemistry, Rize (Turkey); Damla, N. [Batman University, Department of Physics, Batman (Turkey)

    2010-10-15

    In this study, the radiological, structural and chemical characterizations of Mardin-Mazidagi phosphate rock, which is an important phosphate fertilizer source in Turkey were investigated and compared to those of several different phosphate rocks of Tunisia, Egypt, Morocco, Algeria and Syria using gamma spectrometry, X-ray diffraction (XRD) and X-ray fluorescence (XRF) measurement techniques. Elemental analysis results of phosphate samples showed that they were mainly composed of CaO, P{sub 2}O{sub 5}, SiO{sub 2}, Al{sub 2}O{sub 3}, SO{sub 3} and Fe{sub 2}O{sub 3}. Elemental concentrations of U and Th were calculated using {sup 226}Ra and {sup 232}Th activity concentrations, respectively. As a result of XRD analysis, the main peaks of the samples were found to be Fluorapatite (Ca{sub 5}(PO{sub 4}){sub 3}F). The radioactivity concentration levels for {sup 226}Ra, {sup 232}Th and {sup 40}K in all phosphate samples ranged from 250 to 1029 Bq kg{sup -1} with a mean of 535 Bq kg{sup -1}, from 5 to 50 Bq kg{sup -1} with a mean of 20 Bq kg{sup -1} and from 117 to 186 Bq kg{sup -1} with a mean of 148 Bq kg{sup -1}, respectively. The computed values of annual effective doses ranged from 0.17 to 0.59 mSv, with a mean value of 0.33 mSv, which is lower than the recommended limit of 1 mSv y{sup -1} by the International Commission on Radiological Protection.

  1. Stabilization Using Phosphate Bonded Ceramics. Salt Containing Mixed Waste Treatment. Mixed Waste Focus Area. OST Reference No. 117

    Energy Technology Data Exchange (ETDEWEB)

    None, None

    1999-09-01

    Throughout the Department of Energy (DOE) complex there are large inventories of homogeneous mixed waste solids, such as wastewater treatment residues, fly ashes, and sludges that contain relatively high concentrations (greater than 15% by weight) of salts. The inherent solubility of salts (e.g., nitrates, chlorides, and sulfates) makes traditional treatment of these waste streams difficult, expensive, and challenging. One alternative is low-temperature stabilization by chemically bonded phosphate ceramics (CBPCs). The process involves reacting magnesium oxide with monopotassium phosphate with the salt waste to produce a dense monolith. The ceramic makes a strong environmental barrier, and the metals are converted to insoluble, low-leaching phosphate salts. The process has been tested on a variety of surrogates and actual mixed waste streams, including soils, wastewater, flyashes, and crushed debris. It has also been demonstrated at scales ranging from 5 to 55 gallons. In some applications, the CBPC technology provides higher waste loadings and a more durable salt waste form than the baseline method of cementitious grouting. Waste form test specimens were subjected to a variety of performance tests. Results of waste form performance testing concluded that CBPC forms made with salt wastes meet or exceed both RCRA and recommended Nuclear Regulatory Commission (NRC) low-level waste (LLW) disposal criteria. Application of a polymer coating to the CBPC may decrease the leaching of salt anions, but continued waste form evaluations are needed to fully assess the deteriorating effects of this leaching, if any, over time.

  2. Structure of adsorbed monolayers. The surface chemical bond

    Energy Technology Data Exchange (ETDEWEB)

    Somorjai, G.A.; Bent, B.E.

    1984-06-01

    This paper attempts to provide a summary of what has been learned about the structure of adsorbed monolayers and about the surface chemical bond from molecular surface science. While the surface chemical bond is less well understood than bonding of molecules in the gas phase or in the solid state, our knowledge of its properties is rapidly accumulating. The information obtained also has great impact on many surface science based technologies, including heterogeneous catalysis and electronic devices. It is hoped that much of the information obtained from studies at solid-gas interfaces can be correlated with molecular behavior at solid-liquid interfaces. 31 references, 42 figures, 1 table.

  3. Chemical Bond Calculations of Crystal Growth of KDP and ADP

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A novel method was proposed to calculate the crystal morphology (or growth habit) on the basis of chemical bond analysis. All constituent chemical bonds were distinguished as relevant and independent bonds according to their variations during the crystallization process. By employing the current method, the influence of specific growth conditions on the crystal morphology can be considered in the structure analysis process. The ideal morphologies of both KDP (KH2PO4) and ADP (NH4H2PO4) crystals were calculated and compared with our obtained crystallites at room temperature, which validates the present calculation method very well.

  4. The Bondons: The Quantum Particles of the Chemical Bond

    Directory of Open Access Journals (Sweden)

    Mihai V. Putz

    2010-10-01

    Full Text Available By employing the combined Bohmian quantum formalism with the U(1 and SU(2 gauge transformations of the non-relativistic wave-function and the relativistic spinor, within the Schrödinger and Dirac quantum pictures of electron motions, the existence of the chemical field is revealed along the associate bondon particle  characterized by its mass (mΒ, velocity (vΒ, charge (eΒ, and life-time (tΒ. This is quantized either in ground or excited states of the chemical bond in terms of reduced Planck constant ħ, the bond energy Ebond and length Xbond, respectively. The mass-velocity-charge-time quaternion properties of bondons’ particles were used in discussing various paradigmatic types of chemical bond towards assessing their covalent, multiple bonding, metallic and ionic features. The bondonic picture was completed by discussing the relativistic charge and life-time (the actual zitterbewegung problem, i.e., showing that the bondon equals the benchmark electronic charge through moving with almost light velocity. It carries negligible, although non-zero, mass in special bonding conditions and towards observable femtosecond life-time as the bonding length increases in the nanosystems and bonding energy decreases according with the bonding length-energy relationship Ebond[kcal/mol]*Xbond[A]=182019, providing this way the predictive framework in which the particle may be observed. Finally, its role in establishing the virtual states in Raman scattering was also established.

  5. Upper Secondary Teachers' Knowledge for Teaching Chemical Bonding Models

    Science.gov (United States)

    Bergqvist, Anna; Drechsler, Michal; Rundgren, Shu-Nu Chang

    2016-01-01

    Researchers have shown a growing interest in science teachers' professional knowledge in recent decades. The article focuses on how chemistry teachers impart chemical bonding, one of the most important topics covered in upper secondary school chemistry courses. Chemical bonding is primarily taught using models, which are key for understanding science. However, many studies have determined that the use of models in science education can contribute to students' difficulties understanding the topic, and that students generally find chemical bonding a challenging topic. The aim of this study is to investigate teachers' knowledge of teaching chemical bonding. The study focuses on three essential components of pedagogical content knowledge (PCK): (1) the students' understanding, (2) representations, and (3) instructional strategies. We analyzed lesson plans about chemical bonding generated by 10 chemistry teachers with whom we also conducted semi-structured interviews about their teaching. Our results revealed that the teachers were generally unaware of how the representations of models they used affected student comprehension. The teachers had trouble specifying students' difficulties in understanding. Moreover, most of the instructional strategies described were generic and insufficient for promoting student understanding. Additionally, the teachers' rationale for choosing a specific representation or activity was seldom directed at addressing students' understanding. Our results indicate that both PCK components require improvement, and suggest that the two components should be connected. Implications for the professional development of pre-service and in-service teachers are discussed.

  6. Phosphate chemical conversion coatings on metallic substrates for biomedical application: a review.

    Science.gov (United States)

    Liu, Bing; Zhang, Xian; Xiao, Gui-yong; Lu, Yu-peng

    2015-02-01

    Phosphate chemical conversion (PCC) technology has been investigated for improving the surface performance of metallic implants in the biomedical field over the last decade. The metallic materials, such as magnesium and its alloys, titanium, pure iron and stainless steel are widely used as orthopedic devices for immobilization of bone fractures in clinic. They were previously studied as metal substrates for PCC coating aiming to modify their biocompatibility and osteoconductivity. Zinc, calcium and zinc-calcium PCC coatings are frequently utilized considering their nature and the end-use. Although PCC coating has been confirmed to potentially improve the bio-performance of metallic implants in vitro and in vivo by many researchers, there are no unified standards or regulations to give quantitative appraisal of its quality and property. As such, an overview of several main phosphate phases together with their properties and behaviors in vitro and in vivo was conducted. The mechanism of phosphating was also briefly discussed. Critical qualities of PCC coating used for biomedical application including corrosion resistance, wettability and bonding strength were analyzed separately. Biological response including in vitro cell investigations and in vivo tissue response were discussed in terms of the cytocompatibility and bioactivity of PCC coating. Further investigations are proposed to develop appropriate performance evaluation measurements by combining conventional technologies and biomedical procedures.

  7. Chemical cleaning agents and bonding to glass-fiber posts

    Directory of Open Access Journals (Sweden)

    Ana Paula Rodrigues Gonçalves

    2013-02-01

    Full Text Available The influence of chemical cleaning agents on the bond strength between resin cement and glass-fiber posts was investigated. The treatments included 10% hydrofluoric acid, 35% phosphoric acid, 50% hydrogen peroxide, acetone, dichloromethane, ethanol, isopropanol, and tetrahydrofuran. Flat glass-fiber epoxy substrates were exposed to the cleaners for 60 s. Resin cement cylinders were formed on the surfaces and tested in shear. All treatments provided increased bond strength compared to untreated control specimens. All failures were interfacial. Although all agents improved the bond strength, dichloromethane and isopropanol were particularly effective.

  8. Chemical cleaning agents and bonding to glass-fiber posts.

    Science.gov (United States)

    Gonçalves, Ana Paula Rodrigues; Ogliari, Aline de Oliveira; Jardim, Patrícia dos Santos; Moraes, Rafael Ratto de

    2013-01-01

    The influence of chemical cleaning agents on the bond strength between resin cement and glass-fiber posts was investigated. The treatments included 10% hydrofluoric acid, 35% phosphoric acid, 50% hydrogen peroxide, acetone, dichloromethane, ethanol, isopropanol, and tetrahydrofuran. Flat glass-fiber epoxy substrates were exposed to the cleaners for 60 s. Resin cement cylinders were formed on the surfaces and tested in shear. All treatments provided increased bond strength compared to untreated control specimens. All failures were interfacial. Although all agents improved the bond strength, dichloromethane and isopropanol were particularly effective.

  9. Effects of 3% sodium ascorbyl phosphate on the hardness and bond strength of human enamel bleached with 10% carbamide peroxide.

    Science.gov (United States)

    da Silva, Ana Paula Brito; Lima, Adriano Fonseca; Cavalcanti, Andrea Nobrega; Marchi, Giselle Maria

    2010-01-01

    For this study, 120 fragments obtained from human third molars were randomly separated into 12 groups (n = 10). Four groups were used for measuring the Knoop hardness number (KHN) of enamel, while the other eight were used for testing the microtensile bond strength (muTBS) of two adhesive systems (Single Bond and Prime & Bond NT). All groups presented statistically similar KHN values. According to bond strength results, bleached enamel without antioxidant application demonstrated the lowest values of all groups. Based on these results, it could be concluded that the bleaching agents used in the present study (with or without sodium ascorbyl phosphate) did not affect human enamel hardness and that sodium ascorbyl phosphate is able to reverse the compromised bonding in bleached human enamel.

  10. The genesis of the quantum theory of the chemical bond

    CERN Document Server

    Esposito, S

    2013-01-01

    An historical overview is given of the relevant steps that allowed the genesis of the quantum theory of the chemical bond, starting from the appearance of the new quantum mechanics and following later developments till approximately 1931. General ideas and some important details are discussed concerning molecular spectroscopy, as well as quantum computations for simple molecular systems performed within perturbative and variational approaches, for which the Born-Oppenheimer method provided a quantitative theory accounting for rotational, vibrational and electronic states. The novel concepts introduced by the Heitler-London theory, complemented by those underlying the method of the molecular orbitals, are critically analyzed along with some of their relevant applications. Further improvements in the understanding of the nature of the chemical bond are also considered, including the ideas of one-electron and three-electron bonds introduced by Pauling, as well as the generalizations of the Heitler-London theory ...

  11. Combining Hydraulic and Phosphate Bonds to Improve Properties of Alumina-spinel Low Cement Castables

    Institute of Scientific and Technical Information of China (English)

    M.Paghandeh; A.Monshi; R.Emadi

    2009-01-01

    A basic alumina-spinel low cement castables (castables A) and another castables (castables B) with 5% addition of sodium hexametaphosphate were prepared and heat treated at 110 ℃,900 ℃ and 1 400 ℃.It is shown that after heat treating at 110 ℃,cold crushing strength (CCS) of castables B is more than 3 times of castables A and apparent porosity (AP) is less than half of castables A.The presence of 800-1 000 ℃ that hydraulic bond reverses to dehydrate condition and castables A becomes weak with high porosity,castables B shows a CCS more than 4 times of castables A.Needles of magnesium phosphate are responsible for reinforcing microstructure of castables B at 900 ℃.After firing at 1 400 ℃,castables B shows extra ordinary CCS of mare than 100 MPa.Reasons were discussed with X-ray diffraction and scanning electron microscopy.

  12. Chemical Contamination Sensor for Phosphate Ester Hydraulic Fluids

    Directory of Open Access Journals (Sweden)

    Sumit Paul

    2010-01-01

    Full Text Available The paper deals with chemical contamination monitoring in phosphate-ester-based hydraulic fluids using nondispersive infrared (NDIR optical absorption. Our results show that NDIR monitoring allows detecting the take-up of water into such fluids and their hydrolytic disintegration as these become additionally stressed by Joule heating. Observations on the O–H stretching vibration band (3200–3800 cm−1 are used for determining the free water content (0–1.5% and the Total Acid Number (0–1 mgKOH/g. Both quantities can be assessed by monitoring the strength and the asymmetry of the O–H vibration band with regard to the free water absorption band centred around 3500 cm−1. As such optical parameters can be assessed without taking fluid samples from a pressurised hydraulic system, fluid degradation trends can be established based on regular measurements, before irreversible damage to the fluid has occurred. Therefore maintenance actions can be planned accordingly, which is very important for the airline, as unscheduled maintenance disturbs the flights organisation and often generates money loss.

  13. Chemical Bond Analysis of Single Crystal Growth of Magnesium Oxide

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Starting from the crystallographic structure of magnesium oxide (MgO), both the chemical bond model of solids and Pauling's third rule (polyhedral sharing rule) were employed to quantitatively analyze the chemical bonding structure of constituent atoms and single crystal growth. Our analytical results show that MgO single crystals prefer to grow along the direction and the growth rate of the {100} plane is the slowest one. Therefore, the results show that the {100} plane of MgO crystals can be the ultimate morphology face, which is in a good agreement with our previous experimental results. The study indicate that the structure analysis is an effective tool to control the single-crystal growth.

  14. Fast and accurate predictions of covalent bonds in chemical space

    Science.gov (United States)

    Chang, K. Y. Samuel; Fias, Stijn; Ramakrishnan, Raghunathan; von Lilienfeld, O. Anatole

    2016-05-01

    We assess the predictive accuracy of perturbation theory based estimates of changes in covalent bonding due to linear alchemical interpolations among molecules. We have investigated σ bonding to hydrogen, as well as σ and π bonding between main-group elements, occurring in small sets of iso-valence-electronic molecules with elements drawn from second to fourth rows in the p-block of the periodic table. Numerical evidence suggests that first order Taylor expansions of covalent bonding potentials can achieve high accuracy if (i) the alchemical interpolation is vertical (fixed geometry), (ii) it involves elements from the third and fourth rows of the periodic table, and (iii) an optimal reference geometry is used. This leads to near linear changes in the bonding potential, resulting in analytical predictions with chemical accuracy (˜1 kcal/mol). Second order estimates deteriorate the prediction. If initial and final molecules differ not only in composition but also in geometry, all estimates become substantially worse, with second order being slightly more accurate than first order. The independent particle approximation based second order perturbation theory performs poorly when compared to the coupled perturbed or finite difference approach. Taylor series expansions up to fourth order of the potential energy curve of highly symmetric systems indicate a finite radius of convergence, as illustrated for the alchemical stretching of H 2+ . Results are presented for (i) covalent bonds to hydrogen in 12 molecules with 8 valence electrons (CH4, NH3, H2O, HF, SiH4, PH3, H2S, HCl, GeH4, AsH3, H2Se, HBr); (ii) main-group single bonds in 9 molecules with 14 valence electrons (CH3F, CH3Cl, CH3Br, SiH3F, SiH3Cl, SiH3Br, GeH3F, GeH3Cl, GeH3Br); (iii) main-group double bonds in 9 molecules with 12 valence electrons (CH2O, CH2S, CH2Se, SiH2O, SiH2S, SiH2Se, GeH2O, GeH2S, GeH2Se); (iv) main-group triple bonds in 9 molecules with 10 valence electrons (HCN, HCP, HCAs, HSiN, HSi

  15. Chemical Interaction Analysis of an Adhesive Containing 10-Methacryloyloxydecyl Dihydrogen Phosphate (10-MDP) With the Dentin in Noncarious Cervical Lesions.

    Science.gov (United States)

    Oliveira, Bmb; Ulbaldini, Alm; Sato, F; Baesso, M L; Bento, A C; Andrade, Lhc; Lima, S M; Pascotto, R C

    2017-02-03

    The purpose of this study was to evaluate the chemical bonds of a self-etch 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) adhesive to natural noncarious cervical lesions (NCCLs) and compare them with those occurring in sclerotic dentin in artificially prepared defects (APDs). Four human teeth with natural NCCLs on the buccal surface were selected. Artificial defects matching the natural lesions were prepared on the lingual surface of the same teeth serving as control. Micro-Raman (MR) spectroscopy was used to quantify mineral content in natural NCCLs and in APDs. Fourier transform infrared-photoacoustic spectroscopy (FTIR-PAS) readouts were taken before and after adhesive application to analyze the protein matrix/mineral (M:M) ratio and chemical interactions between 10-MDP adhesive and dentin. The MR and FTIR-PAS spectra collected from natural NCCLs demonstrated a larger area of the band (961 cm(-1), PO4) and lower M:M ratio, respectively, characterizing a hypermineralized dentin, compared with APDs. FTIR-PAS demonstrated emergence of a peak (1179 cm(-1), P=O) in spectra after adhesive treatment, demonstrating a more intense chemical interaction in natural NCCLs. The results demonstrated that chemical bonding of 10-MDP adhesive to natural NCCLs is more intense, due to the hypermineralized surface, and suggest that it is unnecessary to remove the hypermineralized layer with burs, as this may decrease the chemical bonding potential of 10-MDP.

  16. Characterization of Electrochemical and Morphological Properties of Iron-Phosphate-Silicate Chemical Garden Structures

    Science.gov (United States)

    Doloboff, I. J.; Barge, L. M.; Russell, M. J.; Kanik, I.

    2012-03-01

    Examination of the growth of Fe^2^+, phosphate, and silicate chemical garden structures to understand properties of similar structures that may have formed at Hadean alkaline hydrothermal vents which may play an important role in the emergence of life.

  17. Phosphate-intercalated Ca-Fe-layered double hydroxides: Crystal structure, bonding character, and release kinetics of phosphate

    Science.gov (United States)

    Woo, Myong A.; Woo Kim, Tae; Paek, Mi-Jeong; Ha, Hyung-Wook; Choy, Jin-Ho; Hwang, Seong-Ju

    2011-01-01

    The nitrate-form of Ca-Fe-layered double hydroxide (Ca-Fe-LDH) was synthesized via co-precipitation method, and its phosphate-intercalates were prepared by ion-exchange reaction. According to X-ray diffraction analysis, the Ca-Fe-LDH-NO 3- compound and its H 2PO 4--intercalate showed hexagonal layered structures, whereas the ion-exchange reaction with HPO 42- caused a frustration of the layer ordering of LDH. Fe K-edge X-ray absorption spectroscopy clearly demonstrated that the Ca-Fe-LDH lattice with trivalent iron ions was well-maintained after the ion-exchange with HPO 42- and H 2PO 4-. Under acidic conditions, phosphate ions were slowly released from the Ca-Fe-LDH lattice and the simultaneous release of hydroxide caused the neutralization of acidic media. Fitting analysis based on kinetic models indicated a heterogeneous diffusion process of phosphates and a distinct dependence of release rate on the charge of phosphates. This study strongly suggested that Ca-Fe-LDH is applicable as bifunctional vector for slow release of phosphate fertilizer and for the neutralization of acid soil.

  18. Mechanisms of Bond Cleavage during Manganese Oxide and UV Degradation of Glyphosate: Results from Phosphate Oxygen Isotopes and Molecular Simulations.

    Science.gov (United States)

    Jaisi, Deb P; Li, Hui; Wallace, Adam F; Paudel, Prajwal; Sun, Mingjing; Balakrishna, Avula; Lerch, Robert N

    2016-11-16

    Degradation of glyphosate in the presence of manganese oxide and UV light was analyzed using phosphate oxygen isotope ratios and density function theory (DFT). The preference of C-P or C-N bond cleavage was found to vary with changing glyphosate/manganese oxide ratios, indicating the potential role of sorption-induced conformational changes on the composition of intermediate degradation products. Isotope data confirmed that one oxygen atom derived solely from water was incorporated into the released phosphate during glyphosate degradation, and this might suggest similar nucleophilic substitution at P centers and C-P bond cleavage both in manganese oxide- and UV light-mediated degradation. The DFT results reveal that the C-P bond could be cleaved by water, OH(-) or (•)OH, with the energy barrier opposing bond dissociation being lowest in the presence of the radical species, and that C-N bond cleavage is favored by the formation of both nitrogen- and carbon-centered radicals. Overall, these results highlight the factors controlling the dominance of C-P or C-N bond cleavage that determines the composition of intermediate/final products and ultimately the degradation pathway.

  19. Porosity of dental phosphate-bonded investments after setting and heating processes.

    Science.gov (United States)

    Asaoka, Kenzo; Bae, Ji-Young; Lee, Hae-Hyoung

    2012-01-01

    Porosities of set and burnout compacts of phosphate-bonded investments were determined. A gas pycnometer was used to measure the volumes, and hence the densities, of fine powders and porous compacts. Porosities of set and burnout compacts were then obtained from these data for as-received powders and dry set compacts by a numerical simulation method, subsequently leading on to the estimated compositions of conventional and rapid-heating investments used in this study. Excess water content in the hardening investment compact was evaluated as a function of setting time elapsed from the start of mixing. Porosities were about 24-32% for set compacts and 43% for burnout compacts, which well agreed with the numerically computed results. It was concluded that the functional composition of investment powder needed to achieve the optimal porosity as well as process parameters such as water-powder (W/P) ratio and keeping time of mixed investment casting slurry before heat treatment could be determined using the numerical simulation method developed in this study.

  20. Majorana, Pauling and the quantum theory of the chemical bond

    CERN Document Server

    Esposito, S

    2013-01-01

    We discuss in detail very little known results obtained by Majorana as early as 1931, regarding the quantum theory of the chemical bond in homopolar molecules, based on the key concept of exchange interaction. After a brief historical overview of the quantum homopolar valence theory, we address the intriguing issues of the formation of the helium molecular ion, He2+, and of the accurate description of the hydrogen molecule, H2. For the first case, the group theory-inspired approach used by Majorana is contrasted with that more known followed by Pauling (and published few months after that of Majorana), while for the second case we focus on his proposal concerning the possible existence of ionic structures in homopolar compounds, just as in the hydrogen molecule. The novelty and relevance of Majorana's results in the modern research on molecular and chemical physics is emphasized as well.

  1. Chemical bonding in TiSb(2) and VSb(2): a quantum chemical and experimental study.

    Science.gov (United States)

    Armbrüster, Marc; Schnelle, Walter; Schwarz, Ulrich; Grin, Yuri

    2007-08-06

    The chemical bonding in the isostructural intermetallic compounds TiSb2 and VSb2, crystallizing in the CuAl2 type, was investigated by means of quantum chemical calculations, particularly the electron localization function (ELF), as well as by Raman spectroscopy, Hall effect and conductivity measurements on oriented single crystals, and high-pressure X-ray powder diffraction. The homogeneity ranges of the compounds were determined by powder X-ray diffraction, WDXS, and DSC measurements. TiSb2 exhibits no significant homogeneity range, while VSb2 shows a small homogeneity range of approximately 0.3 at. %. According to the ELF calculations, the Sb atoms form dumbbells via a two-center two-electron bond, while the T atoms (T = Ti, V) build up chains along the crystallographic c-axis. Both building units are connected by covalent T-Sb-T three-center bonds, thus forming a three-dimensional network. The strength of the bonds involving Sb was determined by fitting a force constant model to the vibrational mode frequencies observed by polarized Raman measurements on oriented single crystals. The resulting bond order of the Sb2 dumbbells is 1, while the strength of the three-center bonds resembles a bond order of 1.5. The weak pressure dependence of the c/a ratio confirms the slightly different bonding picture in TiSb2 compared to that in CuAl2. Electrical transport measurements show the presence of free charge carriers, as well as a metal-like temperature dependence of the electrical resistivity.

  2. On the Chemical Emergence of Phosphate-Based Biochemistry

    Science.gov (United States)

    Kee, Terence

    Contemporary organisms use orthophosphate derivatives (PO43-) in their cell biochemistry,1 yet questions remain as to how Nature was able to accumulate, activate and exploit the or-thophosphate group from geological sources with both poorly solubility and low chemical activ-ity.2 Gulick argued3 a central role for reduced oxidation state phosphorus (P) oxyacids such as H-phosphonates (H2PO3-) and especially H-phosphinates (H2PO2-) in prebiotic chemistry on account of the greater water solubility of their metal salts and, with the presence of P-H bonds, a different reactivity profile to that expected of orthophosphate. The recent demonstration that hydrothermal corrosion of P-rich mineral phases such as schreibersite (Fe,Ni)3P within iron meteorites leads to production of various P-oxyacids including H-phosphonic (H3PO3)4 and H-phosphinic5 acids as well as orthophosphate has reignited interest in reduced oxida-tion state P chemistry in prebiotic environments. We are examining the prebiotic potential of reduced oxidation state P-chemistry through reactions with carbonyl substrates with rea-sonable prebiotic provenance including formaldehyde glycolaldehyde, both intimately involved in the formose reaction for sugar synthesis6 and pyruvic acid,7 a product of glycolysis and feed-stock for the citric acid cycle, a fundamental cellular metablic process whose heritage is considered an ancient one. In this contribution we present some of our latest results on the H-phosphinate-pyruvate system. References: [1] Lodish H et al. (2000) Molecular Cell Biology, 4th Ed., W. H. Freeman Co., New York. [2] Gulick A. (1955) Am. Sci., 43, 479. [3] Gulick A. (1957) Ann. N. Y. Acad. Sci. 69, 309. [4] Pasek M. A. (2008) Proc. Nat. Acad. Sci. USA, 105, 853. [5] Bryant D. E.and Kee T. P. (2006) Chem. Commun. 2344. [6] Weber A. L. (2000) Origins of Life and Evol. Biosph., 30, 33. [7] Cody G. D. et. al. (2000) Science 289, 1337.

  3. Catalysis of hydrolysis and nucleophilic substitution at the P-N bond of phosphoimidazolide-activated nucleotides in phosphate buffers

    Science.gov (United States)

    Kanavarioti, A.; Rosenbach, M. T.

    1991-01-01

    Phosphoimidazolide-activated derivatives of guanosine and cytidine 5'-monophosphates, henceforth called ImpN's, exhibit enhanced rates of degradation in the presence of aqueous inorganic phosphate in the range 4.0 catalysis of the P-N bond hydrolysis by phosphate. The first reaction results in the formation of nucleoside 5'-diphosphate and the second in nucleoside 5'-monophosphate. Analysis of the observed rates as well as the product ratios as a function of pH and phosphate concentration allow distinction between various mechanistic possibilities. The results show that both H2PO4- and HPO4(2-) participate in both hydrolysis and nucleophilic substitution. Statistically corrected biomolecular rate constants indicate that the dianion is 4 times more effective as a general base than the monoanion, and 8 times more effective as nucleophile. The low Bronsted value beta = 0.15 calculated for these phosphate species, presumed to act as general bases in facilitating water attack, is consistent with the fact that catalysis of the hydrolysis of the P-N bond in ImpN's has not been detected before. The beta nuc = 0.35 calculated for water, H2PO4-, HPO4(2-), and hydroxide acting as nucleophiles indicates a more associative transition state for nucleotidyl (O2POR- with R = nucleoside) transfers than that observed for phosphoryl (PO3(2-)) transfers (beta nuc = 0.25). With respect to the stability/reactivity of ImpN's under prebiotic conditions, our study shows that these materials would not suffer additional degradation due to inorganic phosphate, assuming the concentrations of phosphate, Pi, on prebiotic Earth were similar to those in the present oceans ([Pi] approximately 2.25 micromoles).

  4. Implications of protonation and substituent effects for C-O and O-P bond cleavage in phosphate monoesters.

    Science.gov (United States)

    Loncke, Paul G; Berti, Paul J

    2006-05-10

    A recent study of phosphate monoesters that broke down exclusively through C-O bond cleavage and whose reactivity was unaffected by protonation of the nonbridging oxygens (Byczynski et al. J. Am. Chem. Soc. 2003, 125, 12541) raised several questions about the reactivity of phosphate monoesters, R-O-P(i). Potential catalytic strategies, particularly with regard to selectively promoting C-O or O-P bond cleavage, were investigated computationally through simple alkyl and aryl phosphate monoesters. Both C-O and O-P bonds lengthened upon protonating the bridging oxygen, R-O(H(+))-P(i), and heterolytic bond dissociation energies, DeltaH(C)(-)(O) and DeltaH(O)(-)(P), decreased. Which bond will break depends on the protonation state of the phosphoryl moiety, P(i), and the identity of the organosubstituent, R. Protonating the bridging oxygen when the nonbridging oxygens were already protonated favored C-O cleavage, while protonating the bridging oxygen of the dianion form, R-O-PO(3)(2)(-), favored O-P cleavage. Alkyl R groups capable of forming stable cations were more prone to C-O bond cleavage, with tBu > iPr > F(2)iPr > Me. The lack of effect on the C-O cleavage rate from protonating nonbridging oxygens could arise from two precisely offsetting effects: Protonating nonbridging oxygens lengthens the C-O bond, making it more reactive, but also decreases the bridging oxygen proton affinity, making it less likely to be protonated and, therefore, less reactive. The lack of effect could also arise without bridging oxygen protonation if the ratio of rate constants with different protonation states precisely matched the ratio of acidity constants, K(a). Calculations used hybrid density functional theory (B3PW91/6-31++G) methods with a conductor-like polarizable continuum model (CPCM) of solvation. Calculations on Me-phosphate using MP2/aug-cc-pVDZ and PBE0/aug-cc-pVDZ levels of theory, and variations on the solvation model, confirmed the reproducibility with different

  5. Calcium phosphate formation from sea urchin - (brissus latecarinatus) via modified mechano-chemical (ultrasonic) conversion method

    OpenAIRE

    R. Samur; Ozyegin, L.; D. Agaogullari; F. N. Oktar; Agathopoulos, S.; Kalkandelen, C.; I. Duman; B. Ben-Nissan

    2013-01-01

    This study aims to produce apatite structures, such as hydroxyapatite (HA) and fluorapatite (FA), from precursor calcium phosphates of biological origin, namely from sea urchin, with mechano-chemical stirring and hot-plating conversion method. The produced materials were heat treated at 800 °C for 4 hours. X-ray diffraction and scanning electron microscopy (SEM) studies were conducted. Calcium phosphate phases were developed. The SEM images showed the formation of micro to nano-powders. The e...

  6. Is there a chemical interaction between calcium phosphates and organic compounds in the organic/inorganic composites?

    Energy Technology Data Exchange (ETDEWEB)

    Dorozhkin, S.V. [Research Inst. of Fertilisers, Moscow (Russian Federation)

    2001-07-01

    Solid composites of three biologically relevant calcium phosphates and hydroxypropylmethylcellulose (HPMC) were prepared at temperatures of 121 C. Properties of the composites obtained were studied by FTIR, X-ray diffraction, and SEM techniques. Special attention was devoted to seeking of a possible chemical interaction between the calcium phosphates and HPMC. No chemical interaction was found. Thus, HPMC was proven to have no influence on the chemical properties of calcium phosphates. (orig.)

  7. Catalysis of hydrolysis and nucleophilic substitution at the P-N bond of phosphoimidazolide-activated nucleotides in phosphate buffers

    Science.gov (United States)

    Kanavarioti, A.; Rosenbach, M. T.

    1991-01-01

    Phosphoimidazolide-activated derivatives of guanosine and cytidine 5'-monophosphates, henceforth called ImpN's, exhibit enhanced rates of degradation in the presence of aqueous inorganic phosphate in the range 4.0 phosphate. The first reaction results in the formation of nucleoside 5'-diphosphate and the second in nucleoside 5'-monophosphate. Analysis of the observed rates as well as the product ratios as a function of pH and phosphate concentration allow distinction between various mechanistic possibilities. The results show that both H2PO4- and HPO4(2-) participate in both hydrolysis and nucleophilic substitution. Statistically corrected biomolecular rate constants indicate that the dianion is 4 times more effective as a general base than the monoanion, and 8 times more effective as nucleophile. The low Bronsted value beta = 0.15 calculated for these phosphate species, presumed to act as general bases in facilitating water attack, is consistent with the fact that catalysis of the hydrolysis of the P-N bond in ImpN's has not been detected before. The beta nuc = 0.35 calculated for water, H2PO4-, HPO4(2-), and hydroxide acting as nucleophiles indicates a more associative transition state for nucleotidyl (O2POR- with R = nucleoside) transfers than that observed for phosphoryl (PO3(2-)) transfers (beta nuc = 0.25). With respect to the stability/reactivity of ImpN's under prebiotic conditions, our study shows that these materials would not suffer additional degradation due to inorganic phosphate, assuming the concentrations of phosphate, Pi, on prebiotic Earth were similar to those in the present oceans ([Pi] approximately 2.25 micromoles).

  8. Study on the bonding strength between calcium phosphate/chitosan composite coatings and a Mg alloy substrate

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Jie [School of Chemistry Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Pharmacy College, Jiamusi University, Jiamusi 154007 (China); Dai Changsong, E-mail: changsd@hit.edu.cn [School of Chemistry Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); Wei Jie [School of Chemistry Engineering and Technology, Harbin Institute of Technology, Harbin 150001 (China); School of Chemistry and Bioengineering, Suzhou Science Technology University, Suzhou 215009 (China); Wen Zhaohui, E-mail: wenzhaohui1968@163.com [Department of Neuro intern, First Affiliated Hospital of Harbin Medical University, Harbin 150001 (China)

    2012-11-15

    Highlights: Black-Right-Pointing-Pointer Calcium phosphate/chitosan composite coatings on the MAO-AZ91D alloy were prepared. Black-Right-Pointing-Pointer The bonding force between the coating and the magnesium alloy was optimized. Black-Right-Pointing-Pointer The composite coating slowed down the corrosion rate of magnesium alloy in m-SBF. - Abstract: In order to improve the bonding strength between calcium phosphate/chitosan composite coatings and a micro-arc oxidized (MAO)-AZ91D Mg alloy, different influencing parameters were investigated in the process of electrophoretic deposition (EPD) followed by conversion in a phosphate buffer solution (PBS). Surface morphology and phase constituents of the as-prepared materials were investigated by using X-ray diffractometer (XRD), Fourier-transformed infrared spectrophotometer (FTIR), Raman spectrometer, scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS), and a thermo gravimetric and differential thermal analyzer (TG-DTA). Scratch tests were carried out to study the bonding properties between the coatings and the substrates. In vitro immersion tests were conducted to determine the corrosion behaviors of samples with and without deposit layers through electrochemical experiments. In the EPD process, the acetic acid content in the electrophoresis suspension and the electrophoretic voltage played important roles in improving the bonding properties, while the contents of chitosan (CS) and nano-hydroxyapatite (nHA, Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}) in the suspension had less significant influences on the mechanical bonding strength. It was observed that the coatings showed the excellent bonding property when an electrophoretic voltage was in a range of 40-110 V with other reagent amounts as follows: acetic acid: 4.5 vol.%, CS {<=} 0.25 g, nHA {<=} 2.0 g in 200 ml of a CS-acetic acid aqueous solution and nHA {<=} 2.5 g in 300 ml of absolute ethanol. The morphology of the composite coating

  9. Calcium phosphate formation from sea urchin - (brissus latecarinatus via modified mechano-chemical (ultrasonic conversion method

    Directory of Open Access Journals (Sweden)

    R. Samur

    2013-07-01

    Full Text Available This study aims to produce apatite structures, such as hydroxyapatite (HA and fluorapatite (FA, from precursor calcium phosphates of biological origin, namely from sea urchin, with mechano-chemical stirring and hot-plating conversion method. The produced materials were heat treated at 800 °C for 4 hours. X-ray diffraction and scanning electron microscopy (SEM studies were conducted. Calcium phosphate phases were developed. The SEM images showed the formation of micro to nano-powders. The experimental results suggest that sea urchin, Brissus latecarinatus skeleton could be an alternative source for the production of various mono or biphasic calcium phosphates with simple and economic mechano-chemical (ultrasonic conversion method.

  10. Concept of chemical bond and aromaticity based on quantum information theory

    CERN Document Server

    Szilvási, T; Legeza, Ö

    2015-01-01

    Quantum information theory (QIT) emerged in physics as standard technique to extract relevant information from quantum systems. It has already contributed to the development of novel fields like quantum computing, quantum cryptography, and quantum complexity. This arises the question what information is stored according to QIT in molecules which are inherently quantum systems as well. Rigorous analysis of the central quantities of QIT on systematic series of molecules offered the introduction of the concept of chemical bond and aromaticity directly from physical principles and notions. We identify covalent bond, donor-acceptor dative bond, multiple bond, charge-shift bond, and aromaticity indicating unified picture of fundamental chemical models from ab initio.

  11. Rapid preparation of ceramic moulds for medium-sized superalloy castings with magnesia-phosphate-bonded bauxite-mullite investments

    Directory of Open Access Journals (Sweden)

    Li Tingzhong

    2010-11-01

    Full Text Available Phosphate-bonded investments have already been widely utilized in dental restoration and micro-casting of artistic products for its outstanding rapid setting and high strength. However, the rapid setting rate of investment slurry has up to now been a barrier to extend the use of such slurry in preparation of medium-sized ceramic moulds. This paper proposes a new process of rapid fabrication of magnesia-phosphate-bonded investment ceramic moulds for medium-sized superalloy castings utilizing bauxite and mullite as refractory aggregates. In order to determine the properties of magnesia-phosphate-bonded bauxite-mullite investments (MPBBMI, a series of experiments were conducted, including modification of the workable time of slurry by liquid(mL/powder(g(L/P ratio and addition of boric acid as retard agent and sodium tri-polyphosphate (STP as strengthening agent, and adjustment of bauxite (g/mullite(g(B/M ratio for mechanical strength. Mechanical vibration was applied to improve initial setting time and fluidity when pouring investment slurry; then an intermediate size ceramic mould for superalloy castings was manufactured by means of this rapid preparing process with MPBBMI material. The results showed that the MPBBMI slurry exhibits proper initial setting time and excellent fluidity when the L/P ratio is 0.64 and the boric acid content is 0.88wt.%. The fired specimens made from the MPBBMI material demonstrated adequate compression strength to withstand impact force of molten metal when the B/M ratio is 0.89 and the STP content is 0.92wt.%. The experimental results confirmed the feasibility of the proposed rapid fabricating process for medium-sized ceramic moulds with MPBBMI material by appropriate measures.

  12. Chemical Bond Parameters in Sr3MRhO6 (M=Rare earth)

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Chemical bond parameters, that is, bond covalency, bond valence, macroscopic linear susceptibility, and oxidation states of elements in Sr3MRhO6 (M=Sm, Eu, Tb, Dy, Ho, Er, Yb) have been calculated. The results indicate that the bond covalency of M-O decreases sharply with the decrease of ionic radius of M3+ from Sm to Yb, while no obvious trend has been found for Rh-O and Sr-O bonds. The global instability index indicates that the crystal structures of Sr3MrhO6 (M = Sm, Eu, Tb, Dy, Ho) have strained bonds.

  13. Modelling biological and chemically induced precipitation of calcium phosphate in enhanced biological phosphorus removal systems.

    Science.gov (United States)

    Barat, R; Montoya, T; Seco, A; Ferrer, J

    2011-06-01

    The biologically induced precipitation processes can be important in wastewater treatment, in particular treating raw wastewater with high calcium concentration combined with Enhanced Biological Phosphorus Removal. Currently, there is little information and experience in modelling jointly biological and chemical processes. This paper presents a calcium phosphate precipitation model and its inclusion in the Activated Sludge Model No 2d (ASM2d). The proposed precipitation model considers that aqueous phase reactions quickly achieve the chemical equilibrium and that aqueous-solid change is kinetically governed. The model was calibrated using data from four experiments in a Sequencing Batch Reactor (SBR) operated for EBPR and finally validated with two experiments. The precipitation model proposed was able to reproduce the dynamics of amorphous calcium phosphate (ACP) formation and later crystallization to hydroxyapatite (HAP) under different scenarios. The model successfully characterised the EBPR performance of the SBR, including the biological, physical and chemical processes.

  14. Influence of pH on Chemical Forms of Phosphate Adfsorbed on Gothite Surfaces

    Institute of Scientific and Technical Information of China (English)

    LIUFAN; WANGDIAN-FEN; 等

    1995-01-01

    Chemical forms of the phosphate adsorbed on goethite surfaces and characteristics of the coordinate groups which exchange with P on goethite surfaces in solutions with different pll values were investigated.Results showed that the chemical forms of P on goethite surfaces changed from the dominance of monodentate corrdination to that of bidentate one with increasing pH of the solution.By influencing types of phosphate ions in solutions,pH affected the chemical forms of P on goethite surfaces,The amount of OH- displaced by phosphae on goethite surfaces was the most at pH 7.0,the second at pH 9.0,and the least at pH 4.5.

  15. Intermolecular atom-atom bonds in crystals - a chemical perspective.

    Science.gov (United States)

    Thakur, Tejender S; Dubey, Ritesh; Desiraju, Gautam R

    2015-03-01

    Short atom-atom distances between molecules are almost always indicative of specific intermolecular bonding. These distances may be used to assess the significance of all hydrogen bonds, including the C-H⋯O and even weaker C-H⋯F varieties.

  16. Chemical Synthesis, Characterization, and Biocompatibility Study of Hydroxyapatite/Chitosan Phosphate Nanocomposite for Bone Tissue Engineering Applications

    Directory of Open Access Journals (Sweden)

    Nabakumar Pramanik

    2009-01-01

    Full Text Available A novel bioanalogue hydroxyapatite (HAp/chitosan phosphate (CSP nanocomposite has been synthesized by a solution-based chemical methodology with varying HAp contents from 10 to 60% (w/w. The interfacial bonding interaction between HAp and CSP has been investigated through Fourier transform infrared absorption spectra (FTIR and x-ray diffraction (XRD. The surface morphology of the composite and the homogeneous dispersion of nanoparticles in the polymer matrix have been investigated through scanning electron microscopy (SEM and transmission electron microscopy (TEM, respectively. The mechanical properties of the composite are found to be improved significantly with increase in nanoparticle contents. Cytotoxicity test using murine L929 fibroblast confirms that the nanocomposite is cytocompatible. Primary murine osteoblast cell culture study proves that the nanocomposite is osteocompatible and highly in vitro osteogenic. The use of CSP promotes the homogeneous distribution of particles in the polymer matrix through its pendant phosphate groups along with particle-polymer interfacial interactions. The prepared HAp/CSP nanocomposite with uniform microstructure may be used in bone tissue engineering applications.

  17. Preparation and mechanism of calcium phosphate coatings on chemical modified carbon fibers by biomineralization

    Institute of Scientific and Technical Information of China (English)

    HUANG Su-ping; ZHOU Ke-chao; LI Zhi-you

    2008-01-01

    In order to prepare HA coatings on the carbon fibers, chemical modification and biomineralization processes were applied. The phase components, morphologies, and possible growth mechanism of calcium phosphate were studied by infrared spectroscopy(IR), X-ray diffractometry(XRD) and scanning electron microscopy(SEM). The results show that calcium phosphate coating on carbon fibers can be obtained by biomineralization. But the phase components and morphologies of calcium phosphate coatings are different due to different modification methods. Plate-like CaHPO4-2H2O (DCPD) crystals grow from one site of the active centre by HNO3 treatment. While on the para-aminobenzoic acid treated fibers, the coating is composed of nano-structural HA crystal homogeneously. This is because the -COOH functional groups of para-aminobenzoic acid graft on fibers, with negative charge and arranged structure, accelerating the HA crystal nucleation and crystallization on the carbon fibers.

  18. On the hydrates of codeine phosphate: the remarkable influence of hydrogen bonding on the crystal size.

    Science.gov (United States)

    Runčevski, Tomče; Petruševski, Gjorgji; Makreski, Petre; Ugarkovic, Sonja; Dinnebier, Robert E

    2014-07-07

    Codeine phosphate forms three hydrates and two anhydrates. The sesquihydrate and hemihydrate, which differ by one water molecule, are stable at room temperature. The influence of this molecule on the internal crystal structure and how it translates into the external crystal shape are reported.

  19. An alternative empirical model for the relationship between the bond valence and the thermal expansion rate of chemical bonds.

    Science.gov (United States)

    Sidey, Vasyl

    2015-08-01

    The relationship between the bond valence s and the thermal expansion rate of chemical bonds (dr/dT) has been closely approximated by using the alternative three-parameter empirical model (dr/dT) = (u + vs)(-1/w), where u, v and w are the refinable parameters. Unlike the s-(dr/dT) model developed by Brown et al. [(1997), Acta Cryst. B53, 750-761], this alternative model can be optimized for particular s-(dr/dT) datasets in the least-squares refinement procedure. For routine calculations of the thermal expansion rates of chemical bonds, the alternative model with the parameters u = -63.9, v = 2581.0 and w = 0.647 can be recommended.

  20. Nature of the chemical bond and origin of the inverted dipole moment in boron fluoride: a generalized valence bond approach.

    Science.gov (United States)

    Fantuzzi, Felipe; Cardozo, Thiago Messias; Nascimento, Marco Antonio Chaer

    2015-05-28

    The generalized product function energy partitioning (GPF-EP) method has been applied to investigate the nature of the chemical bond and the origin of the inverted dipole moment of the BF molecule. The calculations were carried out with GPF wave functions treating all of the core electrons as a single Hartree-Fock group and the valence electrons at the generalized valence bond perfect-pairing (GVB-PP) or full GVB levels, with the cc-pVTZ basis set. The results show that the chemical structure of both X (1)Σ(+) and a (3)Π states is composed of a single bond. The lower dissociation energy of the excited state is attributed to a stabilizing intraatomic singlet coupling involving the B 2sp-like lobe orbitals after bond dissociation. An increase of electron density on the B atom caused by the reorientation of the boron 2sp-like lobe orbitals is identified as the main responsible effect for the electric dipole inversion in the ground state of BF. Finally, it is shown that π back-bonding from fluorine to boron plays a minor role in the electron density displacement to the bonding region in both states. Moreover, this effect is associated with changes in the quasi-classical component of the electron density only and does not contribute to covalency in either of the states. Therefore, at least for the case of the BF molecule, the term back-bonding is misleading, since it does not contribute to the bond formation.

  1. AIScore chemically diverse empirical scoring function employing quantum chemical binding energies of hydrogen-bonded complexes.

    Science.gov (United States)

    Raub, Stephan; Steffen, Andreas; Kämper, Andreas; Marian, Christel M

    2008-07-01

    In this work we report on a novel scoring function that is based on the LUDI model and focuses on the prediction of binding affinities. AIScore extends the original FlexX scoring function using a chemically diverse set of hydrogen-bonded interactions derived from extensive quantum chemical ab initio calculations. Furthermore, we introduce an algorithmic extension for the treatment of multifurcated hydrogen bonds (XFurcate). Charged and resonance-assisted hydrogen bond energies and hydrophobic interactions as well as a scaling factor for implicit solvation were fitted to experimental data. To this end, we assembled a set of 101 protein-ligand complexes with known experimental binding affinities. Tightly bound water molecules in the active site were considered to be an integral part of the binding pocket. Compared to the original FlexX scoring function, AIScore significantly improves the prediction of the binding free energies of the complexes in their native crystal structures. In combination with XFurcate, AIScore yields a Pearson correlation coefficient of R P = 0.87 on the training set. In a validation run on the PDBbind test set we achieved an R P value of 0.46 for 799 attractively scored complexes, compared to a value of R P = 0.17 and 739 bound complexes obtained with the FlexX original scoring function. The redocking capability of AIScore, on the other hand, does not fully reach the good performance of the original FlexX scoring function. This finding suggests that AIScore should rather be used for postscoring in combination with the standard FlexX incremental ligand construction scheme.

  2. Cytocompatibility assessment of chemical surface treatments for phosphate glass to improve adhesion between glass and polyester.

    Science.gov (United States)

    S Hasan, M; Ahmed, I; Parsons, A J; Walker, G S; Scotchford, C A

    2013-11-01

    Fully resorbable phosphate glass fiber reinforced polymer composites have shown real potential for replacing some of the existing metallic bone fracture fixation devices. However, some of these composites have not provided suitable mechanical strength profiles over the required healing period for bone. Typically, it has been seen that these composites can lose up to 50% or more of their strength within the first week of degradation. Functionalizing the glass surface to promote polymer adhesion or to introduce hydrophobicity at the glass surface could potentially introduce control over the mechanical properties of the composite and their retention. In this study eight chemical agents namely, Glycerol 2-phosphate disodium salt; 3-phosphonopropionic acid; 3-aminopropyltriethoxy silane; etidronic acid; hexamethylene diisocyanate; sorbitol/sodium ended PLA oligomers and amino phosphonic acid, were selected to functionalise the bulk phosphate glass surface. Selected chemical agents had one functional group (-OH or O C N) to react with the glass and another functionality (either -OH, NH2, or Na) to react with the polymer matrix and/or produce hydrophobicity at the fiber surface. Bulk phosphate glass surface-treated with the above agents were assessed for the cytotoxicity of degradation products cell-material interaction in short- and long-term direct cytocompatibility studies. Results obtained from these cytocompatibility studies (using human osteosarcoma (MG63) and primary human osteoblast cell lines) revealed no cytotoxicity from the degradation products and a response comparable to controls in terms of cell functions (attachment, viability, metabolic activity, proliferation, and differentiation) and morphology.

  3. Glutamic Acid Selective Chemical Cleavage of Peptide Bonds.

    Science.gov (United States)

    Nalbone, Joseph M; Lahankar, Neelam; Buissereth, Lyssa; Raj, Monika

    2016-03-04

    Site-specific hydrolysis of peptide bonds at glutamic acid under neutral aqueous conditions is reported. The method relies on the activation of the backbone amide chain at glutamic acid by the formation of a pyroglutamyl (pGlu) imide moiety. This activation increases the susceptibility of a peptide bond toward hydrolysis. The method is highly specific and demonstrates broad substrate scope including cleavage of various bioactive peptides with unnatural amino acid residues, which are unsuitable substrates for enzymatic hydrolysis.

  4. Study on the bonding strength between calcium phosphate/chitosan composite coatings and a Mg alloy substrate

    Science.gov (United States)

    Zhang, Jie; Dai, Chang-Song; Wei, Jie; Wen, Zhao-Hui

    2012-11-01

    In order to improve the bonding strength between calcium phosphate/chitosan composite coatings and a micro-arc oxidized (MAO)-AZ91D Mg alloy, different influencing parameters were investigated in the process of electrophoretic deposition (EPD) followed by conversion in a phosphate buffer solution (PBS). Surface morphology and phase constituents of the as-prepared materials were investigated by using X-ray diffractometer (XRD), Fourier-transformed infrared spectrophotometer (FTIR), Raman spectrometer, scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS), and a thermo gravimetric and differential thermal analyzer (TG-DTA). Scratch tests were carried out to study the bonding properties between the coatings and the substrates. In vitro immersion tests were conducted to determine the corrosion behaviors of samples with and without deposit layers through electrochemical experiments. In the EPD process, the acetic acid content in the electrophoresis suspension and the electrophoretic voltage played important roles in improving the bonding properties, while the contents of chitosan (CS) and nano-hydroxyapatite (nHA, Ca10(PO4)6(OH)2) in the suspension had less significant influences on the mechanical bonding strength. It was observed that the coatings showed the excellent bonding property when an electrophoretic voltage was in a range of 40-110 V with other reagent amounts as follows: acetic acid: 4.5 vol.%, CS ≤ 0.25 g, nHA ≤ 2.0 g in 200 ml of a CS-acetic acid aqueous solution and nHA ≤ 2.5 g in 300 ml of absolute ethanol. The morphology of the composite coating obtained under the above optimal condition had a flake-like crystal structure. The EPD in the nHA/CS-acetic acid/ethanol suspension resulted in hydroxyapatite, chitosan, brushite (DCPD, CaHPO4·2H2O) and Ca(OH)2 in the coatings. After the as-prepared coating materials were immersed into PBS, Ca(OH)2 could be converted into HA and DCPD. The results of the electrochemical tests

  5. Innovations in bonding to zirconia-based materials. Part II: focusing on chemical interactions

    NARCIS (Netherlands)

    M.N. Aboushelib; H. Mirmohamadi; J.P. Matinlinna; E. Kukk; H.F. Ounsi; Z. Salameh

    2009-01-01

    Objectives: The zirconia-resin bond strength was enhanced using novel engineered zirconia primers in combination with selective infiltration etching as a surface pre-treatment. The aim of this study was to evaluate the effect of artificial aging on the chemical stability of the established bond and

  6. Cross-linked PEG via degradable phosphate ester bond: synthesis, water-swelling, and application as drug carrier.

    Science.gov (United States)

    Liu, Zhaoxing; Wang, Lei; Bao, Chunyan; Li, Xinxin; Cao, Lei; Dai, Kerong; Zhu, Linyong

    2011-06-13

    A new series of degradable and water-swellable cross-linked PEG phosphoester polymers (CPPs) based on a facile cross-linked reaction between diphosphoesters of polyethylene glycol (P-PEG-P) and diglycidyl ether of polyethylene glycol (E-PEG-E) has been prepared and characterized. The molecular weights and ratios of the prepolymers played an important role for the properties of CPPs polymers, such as mechanical property, swelling, and degradation rates. In the curing process, the glycidyl ether was consumed by both hydroxyl of the phosphoester (P-OH) and hydroxyl generated from the opened glycidyl ethers (C-OH) with the presence of acid, which generated degradable phosphate esters as cross-linked points and ether bonds as the short branches, respectively. Drug entrapment and release test and biological cytotoxicity studies in vitro suggested that the polymers and generated hydrogels have great potential applications in drug delivery system and biological materials.

  7. Quantum-Mechanical Definition of Atoms and Chemical Bonds in Molecules

    Science.gov (United States)

    2015-01-01

    AFRL-RQ-ED-TR-2014-0025 Quantum-Mechanical Definition of Atoms and Chemical Bonds in Molecules P.W. Langhoff J.D. Mills J.A...manufacture, use, or sell any patented invention that may relate to them. Qualified requestors may obtain copies of this report from the Defense...DATES COVERED (From - To) 15 Oct 2013 - 15 Oct 2014 4. TITLE AND SUBTITLE Quantum-Mechanical Definition of Atoms and Chemical Bonds in Molecules

  8. Chemical stabilisation of lead in shooting range soils with phosphate and magnesium oxide: Synchrotron investigation.

    Science.gov (United States)

    Sanderson, Peter; Naidu, Ravi; Bolan, Nanthi; Lim, Jung Eun; Ok, Yong Sik

    2015-12-15

    Three Australian shooting range soils were treated with phosphate and magnesium oxide, or a combination of both to chemically stabilize Pb. Lead speciation was determined after 1 month ageing by X-ray absorption spectroscopy combined with linear combination fitting in control and treated soils. The predominant Pb species in untreated soils were iron oxide bound Pb, humic acid bound Pb and the mineral litharge. Treatment with phosphate resulted in substantial pyromorphite formation in two of the soils (TV and PE), accounting for up to 38% of Pb species present, despite the addition of excess phosphate. In MgO treated soils only, up to 43% of Pb was associated with MgO. Litharge and Pb hydroxide also formed as a result of MgO addition in the soils. Application of MgO after P treatment increased hydroxypyromorphite/pyromorphite formation relative to soils teated with phosphate only. X-ray diffraction and Scanning electron microscopy revealed PbO precipitate on the surface of MgO. Soil pH, (5.3-9.3) was an important parameter, as was the solubility of existing Pb species. The use of direct means of determination of the stabilisation of metals such as by X-ray absorption spectroscopy is desirable, particularly in relation to understanding long term stability of the immobilised contaminants.

  9. Effects of chemical bonding on heat transport across interfaces.

    Science.gov (United States)

    Losego, Mark D; Grady, Martha E; Sottos, Nancy R; Cahill, David G; Braun, Paul V

    2012-04-22

    Interfaces often dictate heat flow in micro- and nanostructured systems. However, despite the growing importance of thermal management in micro- and nanoscale devices, a unified understanding of the atomic-scale structural features contributing to interfacial heat transport does not exist. Herein, we experimentally demonstrate a link between interfacial bonding character and thermal conductance at the atomic level. Our experimental system consists of a gold film transfer-printed to a self-assembled monolayer (SAM) with systematically varied termination chemistries. Using a combination of ultrafast pump-probe techniques (time-domain thermoreflectance, TDTR, and picosecond acoustics) and laser spallation experiments, we independently measure and correlate changes in bonding strength and heat flow at the gold-SAM interface. For example, we experimentally demonstrate that varying the density of covalent bonds within this single bonding layer modulates both interfacial stiffness and interfacial thermal conductance. We believe that this experimental system will enable future quantification of other interfacial phenomena and will be a critical tool to stimulate and validate new theories describing the mechanisms of interfacial heat transport. Ultimately, these findings will impact applications, including thermoelectric energy harvesting, microelectronics cooling, and spatial targeting for hyperthermal therapeutics.

  10. The Chemical Bond and Solid-state Physics

    Science.gov (United States)

    Phillips, James C.

    1970-01-01

    Proposes a new scale of ionicity, with which the ionic character of bonding in crystals can be predicted and measured. This new scale of ionicity has led to improved understanding of such crystalline properties as lattice structure, heats of formation, elastic constants, and nonlinear optical properties. Bibliography. (LC)

  11. Character of the hard tooth tissue-polymer bond. I. Study of the interaction of calcium phosphate with N-phenylglycine and with N-phenylglycine-glycidyl methacrylate adduct.

    Science.gov (United States)

    Alexieva, C

    1979-09-01

    A model investigation was carried out to establish the chemical character of the bond between hard tooth tissues and polymeric materials. The interaction of NPG and NPG-GMA with Ca3(PO4)2 and 45Ca3(PO4)2 was studied in aqueous, alcoholic and aqueous-alcoholic solutions. It was shown that NPG and NPG-GMA react in solution with Ca ions which are in equilibrium with calcium phosphate. The reaction proceeds more intensively in aqueous-alcoholic medium due to its ionic character. The IR spectra of the reaction products show the presence of NPG-GMA calcium salt.

  12. A qualitative study of high school students' pre- and post instructional conceptions in chemical bonding

    Science.gov (United States)

    Wang, Renhong

    This study investigated high school students' understanding of chemical bonding prior to and after formal chemistry instruction. Two sets of clinical interviews were conducted prior to and after formal instructions on the topic of chemical bonding using a teacher-as-researcher protocol. Twenty-two students enrolled in a New York Regents Chemistry course were interviewed. Six students participated in the pilot study and the other sixteen were involved in the full study. Oral and pictorial data from the interviews were collected and analyzed in two parts; first, the students' conceptual understanding of chemical bonding including common themes, ideas and misconceptions were identified; second, profiles of each student were made to determine conceptual changes due to formal instruction. The findings showed that students were not familiar with the basic components and structure of atoms, especially the electrostatic properties of the sub-atomic particles. Inter-particle distance, rather than the electrostatic forces between particles, was believed to be the determining cause of the state of matter of a substance. The role of repulsive and attractive electrostatic forces in chemical bonding was not recognized. Students were unable to accurately describe the underlying scientific concepts for all types of chemical bonding and revealed a number of misconceptions, which were resistant to change by instruction. Specific areas of difficulty included the accurate descriptions of ionic bonding, covalent bonding and hydrogen bonding. Further, almost all the students could not use electrostatic forces to explain three states of water and phase changes and most students were unable to describe the energy that was released or absorbed due to bond formation or breaking. Student difficulties stemmed from a lack of understanding of some of the underlying, fundamental chemistry, such as the basic atomic structure, the particulate nature of mater and the role of electrostatic forces in

  13. Crystal Structure And Magnetic Property of the Complex of Hydrogen-bonded Two-dimensional Layer Copper(Ⅱ) Acrylate with Trimethyl Phosphate

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@ Copper carboxylate complexes play an important role in catalysing the enzymatic activities[1-4], and the phosphate has an especial use in DNA recognition[5]. Indeed the report about copper carboxylate complexes with phosphate ligands is rare. A chain structure supramolecule [Cu2(CH2CH-COO)4(H2O)2]n has been reported recently[6], in which a Cu2(CH2CH-COO)4(H2O)2 unit is linked by four O(water)-H...O(carboxyl) hydrogen bonds with two adjacent units(Fig.1). In this work a layer structure complex {Cu2(CH2CH-COO)4(H2O)2[OP(OCH3)3]}n was synthesized by means of hydrogen-bonded assembly approach between complex [Cu2(CH2CH-COO)4(H2O)2]n with trimethyl phosphate(TMP).

  14. Developing and validating a chemical bonding instrument for Korean high school students

    Science.gov (United States)

    Jang, Nak Han

    The major purpose of this study was to develop a reliable and valid instrument designed to collect and investigate on Korean high school students' understanding about concepts regarding chemical bonding. The Chemical Bonding Diagnostic Test (CBDT) was developed by the procedure by previously relevant researches (Treagust, 1985; Peterson, 1986; Tan, 1994). The final instrument consisted of 15 two-tier items. The reliability coefficient (Cronbach alpha) for the whole test was 0.74. Also, the range of values for the discrimination index was from 0.38 to 0.90 and the overall average difficulty index was 0.38. The test was administered to 716 science declared students in Korean high school. The 37 common misconceptions on chemical bonding were identified through analysis of the items from the CBDT. The grade 11 students had slightly more misconceptions than the grade 12 students for ionic bonding, covalent bonding, and hydrogen bonding while the grade 12 students had more misconceptions about octet rule and hydrogen bonding than the grade 11 students. From the analysis of ANCOVA, there was no significant difference in grades, and between grade levels and gender on the mean score of CBDT. However, there was a significant difference in gender and a significant interaction between grade levels and chemistry preference. In conclusion, Korean high school students had the most common misconception about the electron configuration on ionic bonding and the water density on hydrogen bonding. Korean students' understanding about the chemical bonding was dependent on the interaction between grade levels and the chemistry preference. Consequently, grade 12 chemistry-preferred students had the highest mean scores among student groups concerned by this study.

  15. Effects of Mechanical and Chemical Pretreatments of Zirconia or Fiber Posts on Resin Cement Bonding.

    Directory of Open Access Journals (Sweden)

    Rui Li

    Full Text Available The bonding strength between resin cement and posts is important for post and core restorations. An important method of improving the bonding strength is the use of various surface pretreatments of the post. In this study, the surfaces of zirconia (fiber posts were treated by mechanical and/or chemical methods such as sandblasting and silanization. The bonding strength between the zirconia (fiber post and the resin cement was measured by a push-out method after thermocycling based on the adhesion to Panavia F 2.0 resin cement. The zirconia and fiber posts exhibited different bonding strengths after sandblasting and/or silanization because of the different strengths and chemical structures. The zirconia post showed a high bonding strength of up to 17.1 MPa after a combined treatment of sandblasting and silanization because of the rough surface and covalent bonds at the interface. This effect was also enhanced by using 1,2-bis(trimethoxysilylethane for the formation of a flexible layer at the interface. In contrast, a high bonding strength of 13.9 MPa was obtained for the fiber post treated by silane agents because the sandblasting treatment resulted in damage to the fiber post, as observed by scanning electron microscopy. The results indicated that the improvement in the bonding strength between the post and the resin cement could be controlled by different chemical and/or mechanical treatments. Enhanced bonding strength depended on covalent bonding and the surface roughness. A zirconia post with high bonding strength could potentially be used for the restoration of teeth in the future.

  16. Initiated chemical vapor deposited nanoadhesive for bonding National Ignition Facility's targets

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Tom [Univ. of California, Berkeley, CA (United States)

    2016-05-19

    Currently, the target fabrication scientists in National Ignition Facility Directorate at Lawrence Livermore National Laboratory (LLNL) is studying the propagation force resulted from laser impulses impacting a target. To best study this, they would like the adhesive used to glue the target substrates to be as thin as possible. The main objective of this research project is to create adhesive glue bonds for NIF’s targets that are ≤ 1 μm thick. Polyglycidylmethacrylate (PGMA) thin films were coated on various substrates using initiated chemical vapor deposition (iCVD). Film quality studies using white light interferometry reveal that the iCVD PGMA films were smooth. The coated substrates were bonded at 150 °C under vacuum, with low inflow of Nitrogen. Success in bonding most of NIF’s mock targets at thicknesses ≤ 1 μm indicates that our process is feasible in bonding the real targets. Key parameters that are required for successful bonding were concluded from the bonding results. They include inert bonding atmosphere, sufficient contact between the PGMA films, and smooth substrates. Average bond strength of 0.60 MPa was obtained from mechanical shearing tests. The bonding failure mode of the sheared interfaces was observed to be cohesive. Future work on this project will include reattempt to bond silica aerogel to iCVD PGMA coated substrates, stabilize carbon nanotube forests with iCVD PGMA coating, and kinetics study of PGMA thermal crosslinking.

  17. First-principles simulations on bonding pathways of chemical transformations under hydrostatic compression

    Science.gov (United States)

    Hu, Anguang; Zhang, Fan

    2012-02-01

    High pressure as a thermodynamic parameter provides a strong structural constraint to lead chemical transformations with selective ways. Thus, chemical transformations under pressure can create novel materials which may not be accessible by covalent synthesis. However, bonding evolution toward high pressure chemical transformations can be a complex process and may happen over widely different pressures. To understand bonding evolution pathways of high pressure chemical transformations, first-principles simulations were performed following hydrostatic compression enthalpy minimization paths to obtain experimentally and theoretically established phase transitions of carbon. The results showed that the chemical transformations from hydrostatic compression carbon to single-bonded phases were characterized by a sudden decrease in principal stress components, indicating the onset of chemical transformation. On this basis, a number of hydrostatic compression chemical transformations from molecular precursors to novel materials were predicted, such as hydrocarbon graphane, a hydrogenated carbon nitride sheet, and carbon nitrides. All predicted hydrostatic compression transformations are featured as a sudden change in principal stress components, representing chemical bonding destruction and formation reactions with a cell volume collapse.

  18. Effect of fluoridated casein phospopeptide-amorphous-calcium phosphate complex, chlorhexidine fluoride mouthwash on shear bond strength of orthodontic brackets: A comparative in vitro study

    Directory of Open Access Journals (Sweden)

    C A Abdul Shahariyar

    2016-01-01

    Full Text Available Objective: The aim of the current study was to determine the effects of casein phosphopeptide amorphous calcium-phosphate (CPP-ACP complex, chlorhexidine fluoride mouthwash on shear bond strengths (SBSs of orthodontic brackets. Materials and Methods: About sixty extracted healthy human premolar teeth with intact buccal enamel were divided into two equal groups to which brackets were bonded using self-etching primers (SEPs and conventional means respectively. These were further equally divided into three subgroups - (1 control (2 CPP-ACP (3 chlorhexidine fluoride mouthwash. The SBSs were then measured using a universal testing machine. Results: SBS of the conventional group was significantly higher than the self-etching group. The intragroup differences were statistically insignificant. Conclusion: CPP-ACP, chlorhexidine fluoride mouthwash did not adversely affect SBS of orthodontic brackets irrespective of the method of conditioning. Brackets bonded with conventional technique showed greater bond strengths as compared to those bonded with SEP.

  19. Relaxation of the chemical bond skin chemisorption size matter ZTP mechanics H2O myths

    CERN Document Server

    Sun, Chang Q

    2014-01-01

    The aim of this book is to explore the detectable properties of a material to the parameters of bond and non-bond involved and to clarify the interdependence of various properties. This book is composed of four parts; Part I deals with the formation and relaxation dynamics of bond and non-bond during chemisorptions with uncovering of the correlation among the chemical bond, energy band, and surface potential barrier (3B) during reactions; Part II is focused on the relaxation of bonds between atoms with fewer neighbors than the ideal in bulk with unraveling of the bond order-length-strength (BOLS) correlation mechanism, which clarifies the nature difference between nanostructures and bulk of the same substance; Part III deals with the relaxation dynamics of bond under heating and compressing with revealing of rules on the temperature-resolved elastic and plastic properties of low-dimensional materials; Part IV is focused on the asymmetric relaxation dynamics of the hydrogen bond (O:H-O) and the anomalous behav...

  20. Electronic parameters of Sr2Nb2O7 and chemical bonding

    DEFF Research Database (Denmark)

    Atuchin, V.V.; Grivel, Jean-Claude; Korotkov, A.S.

    2008-01-01

    /2)) and Delta(O-Sr) = BE(O 1s)-BE(Sr 3d(5/2)), were used to characterize the valence electron transfer on the formation of the Nb-O and Sr-O bonds. The chemical bonding effects were considered on the basis of our XPS results for Sr2Nb2O7 and earlier published structural and XPS data for other Sr- or Nb...

  1. The Synthesis, Structures, and Chemical Properties of Macrocyclic Ligands Covalently Bonded into Layered Arrays

    Energy Technology Data Exchange (ETDEWEB)

    Clearfield, Abraham [Texas A & M Univ., College Station, TX (United States)

    2014-11-01

    In this part of the proposal we have concentrated on the surface functionalization of α-zirconium phosphate of composition Zr(O3POH)2•H2O. It is a layered compound that can be prepared as particles as small as 30 nm to single crystals in the range of cm. This compound is an ion exchanger with a capacity of 6.64 meq per gram. It finds use as a catalyst, proton conductor, sensors, biosensors, in kidney dialysis and drug delivery. By functionalizing the surface additional uses are contemplated as will be described. The layers consist of the metal, with 4+ charge, that is positioned slightly above and below the mean layer plane and bridged by three of the four phosphate oxygens. The remaining POH groups point into the interlayer space creating double rows of POH groups but single arrays on the surface layers. The surface groups are reactive and we were able to bond silanes, isocyanates, epoxides, acrylates ` and phosphates to the surface POH groups. The layers are easily exfoliated or filled with ions by ion exchange or molecules by intercalation reactions. Highlights of our work include, in addition to direct functionalization of the surfaces, replacement of the protons on the surface with ions of different charge. This allows us to bond phosphates, biophosphates, phosphonic acids and alcohols to the surface. By variation of the ion charge of the ions that replace the surface protons, different surface structures are obtained. We have already shown that polymer fillers, catalysts and Janus particles may be prepared. The combination of surface functionalization with the ability to insert molecules and ions between the layers allow for a rich development of numerous useful other applications as well as nano-surface chemistry.

  2. Effects of sandblasting, H2SO4/HCl etching, and phosphate primer application on bond strength of veneering resin composite to commercially pure titanium grade 4

    OpenAIRE

    Egoshi, Takafumi; Taira, Yohsuke; Soeno, Kohyoh; SAWASE Takashi

    2013-01-01

    This study investigated the effects of surface treatments on the bond strength of a resin composite to a commercially pure titanium. The bonding surfaces of all titanium specimens were ground with 1,000-grit silicon carbide paper and then subjected to one or more of these surface treatments: sandblasting with alumina (sand), etching with 45wt% H2SO4 and 15wt% HCl (SH-etchant) at 70°C for 10 min, and/or phosphate primer (MDP-primer) application. Specimens not subjected to any surface treatment...

  3. Chemical and microstructural transformations in lithium iron phosphate battery electrodes following pulsed laser exposure

    Energy Technology Data Exchange (ETDEWEB)

    Lutey, Adrian H.A., E-mail: adrian.lutey2@unibo.it [DIN, Università di Bologna, viale Risorgimento, 2, Bologna (Italy); Fiorini, Maurizio [DICAM, Università di Bologna, via Terracini, 28, Bologna (Italy); Fortunato, Alessandro; Ascari, Alessandro [DIN, Università di Bologna, viale Risorgimento, 2, Bologna (Italy)

    2014-12-15

    Highlights: • Lithium iron phosphate battery electrodes are exposed to pulsed laser radiation. • Raman spectroscopy is performed on regions approaching the incisions and cuts. • Chemical and microstructural changes in the active electrode layers are limited to the visible HAZ. • Some oxidation and degradation of the olive LiFePO{sub 4} cathode active material takes place in the HAZ. • The anode polycrystalline graphite structure becomes less ordered (higher D/G ratio) in the HAZ. - Abstract: Multi-layer lithium iron phosphate (LFP) battery electrodes are exposed to nanosecond pulsed laser radiation of wavelength 1064 nm. Test parameters are chosen to achieve characteristic interaction types ranging from partial incision of the active coating layers only to complete penetration of the electrodes with high visual cut quality. Raman spectroscopy is performed on unexposed regions and at points approaching each incision, highlighting changes in chemical composition and microstructure in the heat affected zone (HAZ). Thermogravimetric analysis is performed on the unexposed electrode active materials to distinguish the development of compositional changes under conditions of slow heating below the melting and sublimation temperatures. A brief theoretical description of the physical phenomena taking place during laser exposure is provided in terms of direct ablation during each laser pulse and vaporization or thermal degradation due to conductive heat transfer on a much longer time-scale, with characteristics of the HAZ reported in terms of these changes. For all laser exposures carried out in the study, chemical and microstructural changes are limited to the visible HAZ. Some degree of oxidation and LFP olivine phase degradation is observed in the cathode, while the polycrystalline graphite structure becomes less ordered in the anode. Where complete penetration is achieved, melting of the cathode active layer and combustion of the anode active layer take place

  4. The role of radial nodes of atomic orbitals for chemical bonding and the periodic table.

    Science.gov (United States)

    Kaupp, Martin

    2007-01-15

    The role of radial nodes, or of their absence, in valence orbitals for chemical bonding and periodic trends is discussed from a unified viewpoint. In particular, we emphasize the special role of the absence of a radial node whenever a shell with angular quantum number l is occupied for the first time (lack of "primogenic repulsion"), as with the 1s, 2p, 3d, and 4f shells. Although the consequences of the very compact 2p shell (e.g. good isovalent hybridization, multiple bonding, high electronegativity, lone-pair repulsion, octet rule) are relatively well known, it seems that some of the aspects of the very compact 3d shell in transition-metal chemistry are less well appreciated, e.g., the often weakened and stretched bonds at equilibrium structure, the frequently colored complexes, and the importance of nondynamical electron-correlation effects in bonding.

  5. Effect of Microwave Radiation on Enzymatic and Chemical Peptide Bond Synthesis on Solid Phase

    Directory of Open Access Journals (Sweden)

    Alessandra Basso

    2009-01-01

    Full Text Available Peptide bond synthesis was performed on PEGA beads under microwave radiations. Classical chemical coupling as well as thermolysin catalyzed synthesis was studied, and the effect of microwave radiations on reaction kinetics, beads' integrity, and enzyme activity was assessed. Results demonstrate that microwave radiations can be profitably exploited to improve reaction kinetics in solid phase peptide synthesis when both chemical and biocatalytic strategies are used.

  6. Halogen bonded supramolecular capsules: a challenging test case for quantum chemical methods.

    Science.gov (United States)

    Sure, Rebecca; Grimme, Stefan

    2016-08-02

    Recently, Diederich et al. synthesized the first supramolecular capsule with a well-defined four-point halogen bonding interaction [Angew. Chem., Int. Ed., 2015, 54, 12339]. This interesting system comprising about 400 atoms represents a challenging test case for accurate quantum chemical methods. We investigate it with our new density functional based composite method for structures and noncovalent interactions (PBEh-3c) as well as our standard protocol for supramolecular thermochemistry and give predictions for chemical modifications to improve the binding strength.

  7. Nuclear radiation as a probe of chemical bonding: the current interplay between theory and experiment

    Energy Technology Data Exchange (ETDEWEB)

    Newton, M D

    1978-01-01

    After a survey of appropriate theoretical formalisms, recent confrontations of theory and experiment in the areas of neutron scattering, Moessbauer spectroscopy, and positron chemistry are discussed, with major emphasis on the degree to which simple concepts of chemical bonding can be refined by complementary use of the above experimental probes and the powerful techniques of computational quantum chemistry.

  8. Isotope effects on chemical shifts in the study of intramolecular hydrogen bonds

    DEFF Research Database (Denmark)

    Hansen, Poul Erik

    2015-01-01

    The paper deals with the use of isotope effects on chemical shifts in characterizing intramolecular hydrogen bonds. Both so-called resonance-assisted (RAHB) and non-RAHB systems are treated. The importance of RAHB will be discussed. Another very important issue is the borderline between “static” ...

  9. Ab Initio Calculations of 31P NMR Chemical Shielding Anisotropy Tensors in Phosphates: Variations Due to Ring Formation

    Directory of Open Access Journals (Sweden)

    Todd M. Alam

    2002-08-01

    Full Text Available Abstract: Ring formation in phosphate systems is expected to influence both the magnitude and orientation of the phosphorus (31P nuclear magnetic resonance (NMR chemical shielding anisotropy (CSA tensor. Ab initio calculations of the 31P CSA tensor in both cyclic and acyclic phosphate clusters were performed as a function of the number of phosphate tetrahedral in the system. The calculation of the 31P CSA tensors employed the GAUSSIAN 98 implementation of the gauge-including atomic orbital (GIAO method at the Hartree-Fock (HF level. It is shown that both the 31P CSA tensor anisotropy, and the isotropic chemical shielding can be used for the identification of cyclic phosphates. The differences between the 31P CSA tensor in acyclic and cyclic phosphate systems become less pronounced with increasing number of phosphate groups within the ring. The orientation of the principal components for the 31P CSA tensor shows some variation due to cyclization, most notably with the smaller, highly strained ring systems.

  10. The influence of feed phosphates on the structural, mechanical and chemical properties of bone tissue in pigs.

    Science.gov (United States)

    Nikodem, A; Dragan, Sz; Kołacz, Sz; Dobrzanski, Z

    2012-01-01

    The aim of the study was to assess the influence of various feed phosphates on the structural and mechanical properties as well as on the chemical composition of femurs in adult pigs (weight approx. 110 kg). Three types of phosphates--monocalcium phosphate (MCP), dicalcium phosphate (n-DCP) and calcium-sodium phosphate (CSP)--were used alternatively in pigs fed with the standard feed mixture. The MCP and CSP phosphates were typical, imported products used traditionally in pig feeding. Dicalcium phosphate (n-DCP) was manufactured in Poland on the basis of phosphoric acid with the new pro-ecological method. The following parameters were determined: the mean physical density of the samples of the compact and spongy bone tissue, values of Young's modulus, strength and the energy of deformation, and Vickers microhardness (HV). Also the content of C, O, Na, Mg, Al, and Si, as well as Ca, P and Sr was determined. Significant differences in mean values of the mentioned parameters occurred between the studied groups. The best mechanical properties were shown by the bones from the n-DCP group, and the compact bone tissue (diaphysis) contained the most Ca, P, and Sr when compared to the MCP and CSP groups.

  11. Chemical interferences when using high gradient magnetic separation for phosphate removal: consequences for lake restoration.

    Science.gov (United States)

    de Vicente, I; Merino-Martos, A; Guerrero, F; Amores, V; de Vicente, J

    2011-09-15

    A promising method for lake restoration is the treatment of lake inlets through the specific adsorption of phosphate (P) on strongly magnetizable particles (Fe) and their subsequent removal using in-flow high gradient magnetic separation (HGMS) techniques. In this work, we report an extensive investigation on the chemical interferences affecting P removal efficiencies in natural waters from 20 Mediterranean ponds and reservoirs. A set of three treatments were considered based on different Fe particles/P concentration ratios. High P removal efficiencies (>80%) were found in freshwater lakes (conductivities<600 μ S cm(-1)). However, a significant reduction in P removal was observed for extremely high mineralized waters. Correlation analysis showed that major cations (Mg(2+), Na(+) and K(+)) and anions (SO(4)(2-) and Cl(-)) played an essential role in P removal efficiency. Comparison between different treatments have shown that when increasing P and Fe concentrations at the same rate or when increasing Fe concentrations for a fixed P concentration, there exist systematic reductions in the slope of the regression lines relating P removal efficiency and the concentration of different chemical variables. These results evidence a general reduction in the chemical competition between P and other ions for adsorption sites on Fe particles. Additional analyses also revealed a reduction in water color, dissolved organic carbon (DOC) and reactive silicate (Si) concentrations with the addition of Fe microparticles.

  12. The role of hydrogen bonding in the thermal expansion and dehydration of brushite, di-calcium phosphate dihydrate

    Science.gov (United States)

    Schofield, P. F.; Knight, K. S.; Houwen, J. A. M. Van Der; Valsami-Jones, E.

    2004-12-01

    The unit-cell and atomic parameters of perdeuterated brushite have been extracted from Rietveld analysis of neutron powder diffraction data within the temperature range 4.2 to 470 K. The thermal expansion of brushite is anisotropic, with the largest expansion along the b axis due principally to the effect of the O(1)···D(4) and O(3)···D(2) hydrogen bonds. Expansion along the c axis, influenced by the Ow1···D(5) interwater hydrogen bond, is also large. The high temperature limits for the expansion coefficients for the unit-cell edges a, b and c are 9.7(5) × 10-6, 3.82(9) × 10-5 and 5.54(5) × 10-5 K-1, respectively, and for the cell volume it is 9.7(1) × 10-5 K-1. The β angle displays oscillatory variation, and empirical data analysis results in αβ = 1.28(3) × 10-6sin(0.0105 T) K-1, within this temperature range. The evolution of the thermal expansion tensor of brushite has been calculated between 50 ≤T≤ 400 K. At 300 K the magnitudes of the principal axes are α11 = 50(6) × 10-6 K-1, α22 = 26.7(7) × 10-6 K-1 and α33 = 7.0(5) × 10-6 K-1. The intermediate axis, α22, is parallel to b, and using IRE convention for the tensor orthonormal basis, the axes α11 and α33 have directions equal to (-0.228, 0, -0.974) and (-0.974, 0, 0.228) respectively. Under the conditions of these experiments, the onset of dehydration occurred at temperatures above 400 K. Bond valence analysis combined with assessments of the thermal evolution of the bonding within brushite suggests that dehydration is precipitated through instabilities in the chemical environment of the second water molecule.

  13. Electron-electron interactions in the chemical bond: ``1/3” Effect in the bond length of hydrogen molecule

    Indian Academy of Sciences (India)

    P Ganguly

    2001-10-01

    The prominent ``1/3” effect observed in the Hall effect plateaus of twodimensional electron gas (2DEG) systems has been postulated to indicating 1/3 fractional charge quasiparticle excitations arising from electron-electron interactions. Tunneling shot-noise experiments on 2DEF exhibiting fractional quantum Hall effect (FQHE) shows evidence for tunnelling of particles with and /3 charges for a constant band mass. A ``1/3” effect in the hydrogen molecule is seen in as much as its internuclear distance, - = - + +, with |+/-| = 1/3. This is examined in terms of electron-electron interactions involving electron- and hole quasiparticles, (-) and (ℎ+), equivalent to those observed in FQHE shot-noise experiments. The (/) ratio of the (-) and (ℎ+) quasiparticles is kept at 1: -3. Instead of a 2DEG, these particles are treated as being in flat Bohr orbits. A treatment in the language of charge-flux tube composites for the hydrogen atom as well as the hydrogen molecule is attempted. Such treatment gives important insights into changes in chemical potential and bond energy on crossing a phase boundary during the atom-bond transition as well as on models for FQHE itself.

  14. Electronic structure and chemical bonding of Li4Pt3Si

    Science.gov (United States)

    Matar, S. F.; Pöttgen, R.; Al Alam, A. F.; Ouaini, N.

    2012-07-01

    The electronic structure of rhombohedral Li4Pt3Si (space group R32) is examined from ab initio with an assessment of the properties of chemical bonding relating to the presence of different Li and Pt Wyckoff sites. The structure with totally de-intercalated Li keeps the characteristics of the pristine compound with a reduction of the volume albeit with less cohesive energy. The binding energies of Li point to different bonding intensities according to their different Wyckoff sites and indicate the possibility of delithiation.

  15. Influence of precursor solution parameters on chemical properties of calcium phosphate coatings prepared using Electrostatic Spray Deposition (ESD).

    NARCIS (Netherlands)

    Leeuwenburgh, S.C.G.; Wolke, J.G.C.; Schoonman, J.; Jansen, J.A.

    2004-01-01

    A novel coating technique, referred to as Electrostatic Spray Deposition (ESD), was used to deposit calcium phosphate (CaP) coatings with a variety of chemical properties. The relationship between the composition of the precursor solutions and the crystal and molecular structure of the deposited coa

  16. Effect of added phosphate and type of cooking method on physico-chemical and sensory features of cooked lamb loins.

    Science.gov (United States)

    Roldán, Mar; Antequera, Teresa; Pérez-Palacios, Trinidad; Ruiz, Jorge

    2014-05-01

    This study evaluated the effect of brining with phosphates on the physico-chemical and sensory features of sous-vide and roasted cooked lamb. Lamb loins (n=48) were injected with either 10% w/w of distilled water or a solution containing 0.2% or 0.4% (w/v) of a mixture of phosphate salts. After injection, samples were either sous-vide cooked (12h-60°C) or oven roasted (180°C until 73°C of core temp.). Expressible moisture, cooking loss, instrumental color, pH, water holding capacity, instrumental texture and sensory properties were evaluated. Brining with phosphates led to lower cooking loss in both sous-vide and oven roasted samples, but only the former showed significantly higher moisture content. Phosphates increased instrumental hardness and shear force values in sous-vide samples, while this effect was not as evident in roasted ones. Toughness was reduced and juiciness was improved as a consequence of phosphate addition. Overall, injection of a phosphate solution appears as a potential procedure for improving sensory textural features of cooked lamb whole cuts.

  17. Mapping lipid and collagen by multispectral photoacoustic imaging of chemical bond vibration

    Science.gov (United States)

    Wang, Pu; Wang, Ping; Wang, Han-Wei; Cheng, Ji-Xin

    2012-09-01

    Photoacoustic microscopy using vibrational overtone absorption as a contrast mechanism allows bond-selective imaging of deep tissues. Due to the spectral similarity of molecules in the region of overtone vibration, it is difficult to interrogate chemical components using photoacoustic signal at single excitation wavelength. Here we demonstrate that lipids and collagen, two critical markers for many kinds of diseases, can be distinguished by multispectral photoacoustic imaging of the first overtone of C-H bond. A phantom consisting of rat-tail tendon and fat was constructed to demonstrate this technique. Wavelengths between 1650 and 1850 nm were scanned to excite both the first overtone and combination bands of C-H bonds. B-scan multispectral photoacoustic images, in which each pixel contains a spectrum, were analyzed by a multivariate curve resolution-alternating least squares algorithm to recover the spatial distribution of collagen and lipids in the phantom.

  18. Studying Chemical Reactions, One Bond at a Time, with Single Molecule AFM Techniques

    Science.gov (United States)

    Fernandez, Julio M.

    2008-03-01

    The mechanisms by which mechanical forces regulate the kinetics of a chemical reaction are unknown. In my lecture I will demonstrate how we use single molecule force-clamp spectroscopy and protein engineering to study the effect of force on the kinetics of thiol/disulfide exchange. Reduction of disulfide bond via the thiol/disulfide exchange chemical reaction is crucial in regulating protein function and is of common occurrence in mechanically stressed proteins. While reduction is thought to proceed through a substitution nucleophilic bimolecular (SN2) reaction, the role of a mechanical force in modulating this chemical reaction is unknown. We apply a constant stretching force to single engineered disulfide bonds and measure their rate of reduction by dithiothreitol (DTT). We find that while the reduction rate is linearly dependent on the concentration of DTT, it is exponentially dependent on the applied force, increasing 10-fold over a 300 pN range. This result predicts that the disulfide bond lengthens by 0.34 å at the transition state of the thiol/disulfide exchange reaction. In addition to DTT, we also study the reduction of the engineered disulfide bond by the E. coli enzyme thioredoxin (Trx). Thioredoxins are enzymes that catalyze disulfide bond reduction in all organisms. As before, we apply a mechanical force in the range of 25-450 pN to the engineered disulfide bond substrate and monitor the reduction of these bonds by individual enzymes. In sharp contrast with the data obtained with DTT, we now observe two alternative forms of the catalytic reaction, the first requiring a reorientation of the substrate disulfide bond, causing a shortening of the substrate polypeptide by 0.76±0.07 å, and the second elongating the substrate disulfide bond by 0.21±0.01 å. These results support the view that the Trx active site regulates the geometry of the participating sulfur atoms, with sub-ångström precision, in order to achieve efficient catalysis. Single molecule

  19. Evidence for chemical bond formation at rubber-brass interface: Photoelectron spectroscopy study of bonding interaction between copper sulfide and model molecules of natural rubber

    Science.gov (United States)

    Ozawa, Kenichi; Mase, Kazuhiko

    2016-12-01

    Strong adhesion between rubber and brass has been considered to arise mainly from the mechanical interaction, which is characterized by dendritic interlocking at the interface. In order to examine a possible contribution of the chemical interaction, chemical state analysis was carried out for model molecules of natural rubber (2-methyl-2-butene and isoprene) adsorbed on Cu2S, a key chemical species for adhesion, by means of photoelectron spectroscopy (PES). Absence of a C 1s PES component associated with C=C bonds and the appearance of adsorption-induced components in the S 2p region indicate that the molecules interact with the Cu2S surface via the C=C bond to form C-S covalent bonds. This proves that the chemical interaction certainly plays a role in rubber-brass adhesion along with the mechanical interaction.

  20. In vitro evaluation of casein phosphopeptide-amorphous calcium phosphate effect on the shear bond strength of dental adhesives to enamel

    Science.gov (United States)

    Shadman, Niloofar; Ebrahimi, Shahram Farzin; Shoul, Maryam Azizi; Sattari, Hasti

    2015-01-01

    Background: Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) is applied for remineralization of early caries lesions or tooth sensitivity conditions and may affect subsequent resin bonding. This in vitro study investigated the effect of CPP-ACP on the shear bond strength of dental adhesives to enamel. Materials and Methods: Sixty extracted human molar teeth were selected and randomly divided into three groups and six subgroups. Buccal or lingual surfaces of teeth were prepared to create a flat enamel surface. Adhesives used were Tetric N-Bond, AdheSE and AdheSE One F. In three subgroups, before applying adhesives, enamel surfaces were treated with Tooth Mousse CPP-ACP for one hour, rinsed and stored in 37°C temperature with 100% humidity. This procedure was repeated for 5 days and then adhesives were applied and Tetric N-Ceram composite was adhered to the enamel. This procedure was also fulfilled for the other three subgroups without CPP-ACP treatment. After 24 hour water storage, samples were tested for shear bond strength test in a universal testing machine. Failure modes were determined by stereomicroscope. Data were analyzed by t-test and one-way analysis of variance with P 0.05). In non-applied CPP-ACP subgroups, there were statistically significant differences among all subgroups. Tetric N-Bond had the highest and AdheSE One F had the lowest shear bond strength. Conclusion: CPP-ACP application reduces the shear bond strength of AdheSE and AdheSE One F to enamel but not Tetric N-Bond. PMID:25878683

  1. In vitro evaluation of casein phosphopeptide-amorphous calcium phosphate effect on the shear bond strength of dental adhesives to enamel

    Directory of Open Access Journals (Sweden)

    Niloofar Shadman

    2015-01-01

    Full Text Available Background: Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP is applied for remineralization of early caries lesions or tooth sensitivity conditions and may affect subsequent resin bonding. This in vitro study investigated the effect of CPP-ACP on the shear bond strength of dental adhesives to enamel. Materials and Methods: Sixty extracted human molar teeth were selected and randomly divided into three groups and six subgroups. Buccal or lingual surfaces of teeth were prepared to create a flat enamel surface. Adhesives used were Tetric N-Bond, AdheSE and AdheSE One F. In three subgroups, before applying adhesives, enamel surfaces were treated with Tooth Mousse CPP-ACP for one hour, rinsed and stored in 37°C temperature with 100% humidity. This procedure was repeated for 5 days and then adhesives were applied and Tetric N-Ceram composite was adhered to the enamel. This procedure was also fulfilled for the other three subgroups without CPP-ACP treatment. After 24 hour water storage, samples were tested for shear bond strength test in a universal testing machine. Failure modes were determined by stereomicroscope. Data were analyzed by t-test and one-way analysis of variance with P 0.05. In non-applied CPP-ACP subgroups, there were statistically significant differences among all subgroups. Tetric N-Bond had the highest and AdheSE One F had the lowest shear bond strength. Conclusion: CPP-ACP application reduces the shear bond strength of AdheSE and AdheSE One F to enamel but not Tetric N-Bond.

  2. Developing density functional theory for Bose-Einstein condensates. The case of chemical bonding

    Energy Technology Data Exchange (ETDEWEB)

    Putz, Mihai V., E-mail: mvputz@cbg.uvt.ro [Laboratory of Physical and Computational Chemistry, Chemistry Department, West University of Timisoara, Str. Pestalozzi No. 16, 300115 Timisoara, Romania and Theoretical Physics Institute, Free University Berlin, Arnimallee 14, 14195 Berlin (Germany)

    2015-01-22

    Since the nowadays growing interest in Bose-Einstein condensates due to the expanded experimental evidence on various atomic systems within optical lattices in weak and strong coupling regimes, the connection with Density Functional Theory is firstly advanced within the mean field framework at three levels of comprehension: the many-body normalization condition, Thomas-Fermi limit, and the chemical hardness closure with the inter-bosonic strength and universal Hohenberg-Kohn functional. As an application the traditional Heitler-London quantum mechanical description of the chemical bonding for homopolar atomic systems is reloaded within the non-linear Schrödinger (Gross-Pitaevsky) Hamiltonian; the results show that a two-fold energetic solution is registered either for bonding and antibonding states, with the bosonic contribution being driven by the square of the order parameter for the Bose-Einstein condensate density in free (gas) motion, while the associate wave functions remain as in classical molecular orbital model.

  3. Detection of sub-GeV Dark Matter and Solar Neutrinos via Chemical-Bond Breaking

    CERN Document Server

    Essig, Rouven; Slone, Oren; Volansky, Tomer

    2016-01-01

    We explore a new low-threshold direct-detection concept for dark matter, based on the breaking of chemical bonds between atoms. This includes the dissociation of molecules and the creation of defects in a lattice. With thresholds of a few to 10's of eV, such an experiment could probe the nuclear couplings of dark matter particles as light as a few MeV. We calculate the expected rates for dark matter to break apart diatomic molecules, which we take as a case study for more general systems. We briefly mention ideas for how chemical-bond breaking might be detected in practice. We also discuss the possibility of detecting solar neutrinos, including pp neutrinos, with this experimental concept. With an event rate of $\\mathcal{O}$(0.1/kg-year), large exposures are required, but measuring low-energy solar neutrinos would provide a crucial test of the solar model.

  4. Chemical bonding and charge density distribution analysis of undoped and lanthanum doped barium titanate ceramics

    Indian Academy of Sciences (India)

    J MANGAIYARKKARASI; R SARAVANAN; MUKHLIS M ISMAIL

    2016-12-01

    A-site deficient, Lanthanum substituted Ba1−xLa2x/3TiO3 (x=0.000, 0.005, 0.015, 0.020 and 0.025) ceramics have been synthesized by chemical route. The effects of lanthanum dopant on the BaTiO3 lattice and the electron density distributions in the unit cell of the samples were investigated. Structural studies suggested the reduction in cell parameters and shrinkage in cell volume with the increase in lanthanum content. Chemical bonding and electron density distributions were examined through high resolution maximum entropy method (MEM). The mid bond electron density values revealed the enhancement of covalent nature between titanium and oxygen ions and predominant ionic nature between barium and oxygen ions. Average grain sizes were estimated for the undoped and doped samples. SEM investigations showed the existence of smaller grains with large voids in between them.

  5. Investigation of Chemical Bond Properties and Mssbauer Spectroscopy in YBa2Cu3O7

    Institute of Scientific and Technical Information of China (English)

    高发明; 李东春; 张思远

    2003-01-01

    Chemical bond properties of YBa2Cu3O7 were studied by using the average band-gap model. The calculated results show that the covalency of Cu(1)-O bond is 0.406, and one of Cu(2)-O is 0.276. Mssbauer isomer shifts of 57Fe in Y-123 were calculated by the chemical surrounding factor hv defined by covalency and electronic polarizability. The charge-state and site of Fe were determined. The relation between the coupling constant of electron-phonon interaction and covalency is employed to explain that the Cu(2)-O plane is more important than the Cu(1)-O chain on the superconductivity in the Y-123 compounds.

  6. Influence of dentin pretreatment with synthetic hydroxyapatite application on the bond strength of fiber posts luted with 10-methacryloyloxydecyl dihydrogen phosphate-containing luting systems.

    Science.gov (United States)

    Scotti, Nicola; Bergantin, Emanuele; Tempesta, Riccardo; Turco, Gianluca; Breschi, Lorenzo; Farina, Elena; Pasqualini, Damiano; Berutti, Elio

    2016-10-01

    The aim of this in vitro study was evaluate the effect of application of synthetic hydroxyapatite on fiber post bond strength to radicular dentine. Forty, single-root teeth were endodontically treated and an 8 mm post space was prepared. Specimens were randomly placed in four groups (n = 10 in each) and treated using the following fiber post luting procedures: group 1, 17% EDTA + Panavia SA; group 2, 17% EDTA + Teethmate Desensitizer + Panavia SA; group 3, All-Bond Universal + Duo-Link Universal; and group 4, All-Bond Universal + Teethmate Desensitizer + Duo-Link Universal. Fiber posts were luted in the post space and light-cured for 120 s using a light-emitting diode (LED) lamp. After 7 d of storage at 37°C, the teeth were cut into 1-mm-thick slices, which were subjected to a push-out test until failure using a universal testing machine. Two specimens per group were prepared for scanning electron microscopy analysis. An energy-dispersive X-ray spectroscopy detector was used for elemental analysis of the specimen surface. The results were statistically analyzed using one-way anova. The fiber post bond strength was statistically significantly increased after the application of Teethmate Desensitizer to post space walls, either with a 10-MDP-containing self-adhesive cement or with a universal adhesive. Scanning electron microscopy and EDAX analysis showed that Teethmate Desensitizer created a calcium phosphate precipitate over post space dentinal tubules, which significantly improved the bond strength of the fiber post luted with 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP)-containing adhesive systems.

  7. Chemical Reasoning Based on an Invariance Property: Bond and Lone Pair Pictures in Quantum Structural Formulas

    Directory of Open Access Journals (Sweden)

    Joseph Alia

    2010-07-01

    Full Text Available Chemists use one set of orbitals when comparing to a structural formula, hybridized AOs or NBOs for example, and another for reasoning in terms of frontier orbitals, MOs usually. Chemical arguments can frequently be made in terms of energy and/or electron density without the consideration of orbitals at all. All orbital representations, orthogonal or not, within a given function space are related by linear transformation. Chemical arguments based on orbitals are really energy or electron density arguments; orbitals are linked to these observables through the use of operators. The Valency Interaction Formula, VIF, offers a system of chemical reasoning based on the invariance of observables from one orbital representation to another. VIF pictures have been defined as one-electron density and Hamiltonian operators. These pictures are classified in a chemically meaningful way by use of linear transformations applied to them in the form of two pictorial rules and the invariance of the number of doubly, singly, and unoccupied orbitals or bonding, nonbonding, and antibonding orbitals under these transformations. The compatibility of the VIF method with the bond pair – lone pair language of Lewis is demonstrated. Different electron lone pair representations are related by the pictorial rules and have stability understood in terms of Walsh’s rules. Symmetries of conjugated ring systems are related to their electronic state by simple mathematical formulas. Description of lone pairs in conjugated systems is based on the strength and sign of orbital interactions around the ring. Simple models for bonding in copper clusters are tested, and the bonding of O2 to Fe(II in hemoglobin is described. Arguments made are supported by HF, B3LYP, and MP2 computations.

  8. Multi-layered, chemically bonded lithium-ion and lithium/air batteries

    Science.gov (United States)

    Narula, Chaitanya Kumar; Nanda, Jagjit; Bischoff, Brian L; Bhave, Ramesh R

    2014-05-13

    Disclosed are multilayer, porous, thin-layered lithium-ion batteries that include an inorganic separator as a thin layer that is chemically bonded to surfaces of positive and negative electrode layers. Thus, in such disclosed lithium-ion batteries, the electrodes and separator are made to form non-discrete (i.e., integral) thin layers. Also disclosed are methods of fabricating integrally connected, thin, multilayer lithium batteries including lithium-ion and lithium/air batteries.

  9. Shear Bond Strength of MDP-Containing Self-Adhesive Resin Cement and Y-TZP Ceramics: Effect of Phosphate Monomer-Containing Primers

    Directory of Open Access Journals (Sweden)

    Jin-Soo Ahn

    2015-01-01

    Full Text Available Purpose. This study was conducted to evaluate the effects of different phosphate monomer-containing primers on the shear bond strength between yttria-tetragonal zirconia polycrystal (Y-TZP ceramics and MDP-containing self-adhesive resin cement. Materials and Methods. Y-TZP ceramic surfaces were ground flat with #600-grit SiC paper and divided into six groups (n=10. They were treated as follows: untreated (control, Metal/Zirconia Primer, Z-PRIME Plus, air abrasion, Metal/Zirconia Primer with air abrasion, and Z-PRIME Plus with air abrasion. MDP-containing self-adhesive resin cement was applied to the surface-treated Y-TZP specimens. After thermocycling, a shear bond strength test was performed. The surfaces of the Y-TZP specimens were analyzed under a scanning electron microscope. The bond strength values were statistically analyzed using one-way analysis of variance and the Student–Newman–Keuls multiple comparison test (P<0.05. Results. The Z-PRIME Plus treatment combined with air abrasion produced the highest bond strength, followed by Z-PRIME Plus application, Metal/Zirconia Primer combined with air abrasion, air abrasion alone, and, lastly, Metal/Zirconia Primer application. The control group yielded the lowest results (P<0.05. Conclusion. The application of MDP-containing primer resulted in increased bond strength between Y-TZP ceramics and MDP-containing self-adhesive resin cements.

  10. Chemically-bonded brick production based on burned clay by means of semidry pressing

    Energy Technology Data Exchange (ETDEWEB)

    Voroshilov, Ivan, E-mail: Nixon.06@mail.ru; Endzhievskaya, Irina, E-mail: icaend@mail.ru; Vasilovskaya, Nina, E-mail: icaend@mail.ru [FSAEI HVE Siberian Federal University, 82 Svobodny Prospekt, Krasnoyarsk, 660130 (Russian Federation)

    2016-01-15

    We presented a study on the possibility of using the burnt rocks of the Krasnoyarsk Territory for production of chemically-bonded materials in the form of bricks which are so widely used in multistory housing and private house construction. The radiographic analysis of the composition of burnt rock was conducted and a modifier to adjust the composition uniformity was identified. The mixing moisture content was identified and optimal amount at 13-15% was determined. The method of semidry pressing has been chosen. The process of obtaining moldings has been theoretically proved; the advantages of chemically-bonded wall materials compared to ceramic brick were shown. The production of efficient artificial stone based on material burnt rocks, which is comparable with conventionally effective ceramic materials or effective with cell tile was proved, the density of the burned clay-based cell tile makes up to 1630-1785 kg \\ m{sup 3}, with compressive strength of 13.6-20.0 MPa depending on the compression ratio and cement consumption, frost resistance index is F50, and the thermal conductivity in the masonry is λ = 0,459-0,546 W \\ m {sup *} °C. The clear geometric dimensions of pressed products allow the use of the chemically-bonded brick based on burnt clay as a facing brick.

  11. Non-standard tests for process control in chemically bonded sands

    Directory of Open Access Journals (Sweden)

    S. Ramrattan

    2016-01-01

    Full Text Available Chemically bonded sand cores and molds are more commonly referred to as precision sand systems in the high production automotive powertrain sector. Their behavior in contact with molten metal can lead to casting defects. Consequently, the interaction is of great interest and an important part of metal casting technology. The American Foundry Society (AFS sand testing is based on physical, mechanical, thermal and chemical properties of the sand system. Foundry engineers have long known that certain AFS sand tests provide limited information regarding control of molding and casting quality. The inadequacy is due to the fact that sand casting processes are inherently thermo-mechanical, thermo-chemical and thermo-physical. Non-standard foundry sand testing has proven useful for laboratory measurement of these characteristics in foundry sand using a disc-shaped specimen. Similarly, the equivalent disc-shaped specimens are used for casting trials. In order to accomplish near-net-shape casting with minimal defects, it is necessary to understand both the properties of the sand system, as well as the interface of molten metal when different binders, additives and/or refractory coatings are used. The methodology for the following non-standard chemically bonded sand tests is described: (1 disc transverse; (2 impact; (3 modified permeability; (4 abrasion; (5 thermal distortion; (6 quick loss on ignition. The data related to the non-standard sand tests were analyzed and interpreted. The test results indicate that there is relatively lower test-to-test variability with the disc-shaped specimens. The non-standard tests were able to discriminate between the chemically bonded polyurethane cold box sand specimens. Further studies should be conducted on various other sand and binder systems as well as on different specimen thicknesses.

  12. Efficiency of horizontal roughing filter in removing nitrate, phosphate and chemical oxygen demand from effluent of waste stabilization pond

    Directory of Open Access Journals (Sweden)

    Seyed Mostafa Khezri

    2015-06-01

    Full Text Available Background: The effective size of the end grain of horizontal roughing filters (HRFs is larger than 2 mm. This study aimed to examine the efficiency of HRFs in removing nitrate, phosphate, and chemical oxygen demand (COD from effluent of a wastewater stabilization pond. Methods: This experimental study was conducted in 2013. The pilot project was transferred to the Karaj wastewater treatment plant (stabilization pond, and the installation, equipping, and start-up of the system began using an effluent treatment plant. Sampling was done from March to August in 3 rates, 0.5, 1 and 1.5 m/h, and included simultaneous sampling from inlet and outlet filtering to determine the concentrations of nitrate, phosphate, and COD. Results: At filtration rates of 0.5, 1, and 1.5 m/h, the average nitrate removal equaled 25%, 32%, and 34%, respectively, average phosphate removal equaled 29%, 26%, and 28%, respectively, and the average COD removal at filtration rates of 0.5, 1, and 1.5 m/h equaled 62%, 66%, and 68%, respectively. Outlet values of phosphate and nitrate were lower than the standards set by the Environmental Standards Organization (ESO (P < 0.05. Conclusion: According to the results of this study, the HRF function was approximately adequate in COD removal, but its efficiency in nitrate and phosphate removal was lower.

  13. Four chemical methods of porcelain conditioning and their influence over bond strength and surface integrity

    Science.gov (United States)

    Stella, João Paulo Fragomeni; Oliveira, Andrea Becker; Nojima, Lincoln Issamu; Marquezan, Mariana

    2015-01-01

    OBJECTIVE: To assess four different chemical surface conditioning methods for ceramic material before bracket bonding, and their impact on shear bond strength and surface integrity at debonding. METHODS: Four experimental groups (n = 13) were set up according to the ceramic conditioning method: G1 = 37% phosphoric acid etching followed by silane application; G2 = 37% liquid phosphoric acid etching, no rinsing, followed by silane application; G3 = 10% hydrofluoric acid etching alone; and G4 = 10% hydrofluoric acid etching followed by silane application. After surface conditioning, metal brackets were bonded to porcelain by means of the Transbond XP system (3M Unitek). Samples were submitted to shear bond strength tests in a universal testing machine and the surfaces were later assessed with a microscope under 8 X magnification. ANOVA/Tukey tests were performed to establish the difference between groups (α= 5%). RESULTS: The highest shear bond strength values were found in groups G3 and G4 (22.01 ± 2.15 MPa and 22.83 ± 3.32 Mpa, respectively), followed by G1 (16.42 ± 3.61 MPa) and G2 (9.29 ± 1.95 MPa). As regards surface evaluation after bracket debonding, the use of liquid phosphoric acid followed by silane application (G2) produced the least damage to porcelain. When hydrofluoric acid and silane were applied, the risk of ceramic fracture increased. CONCLUSIONS: Acceptable levels of bond strength for clinical use were reached by all methods tested; however, liquid phosphoric acid etching followed by silane application (G2) resulted in the least damage to the ceramic surface. PMID:26352845

  14. Four chemical methods of porcelain conditioning and their influence over bond strength and surface integrity

    Directory of Open Access Journals (Sweden)

    João Paulo Fragomeni Stella

    2015-08-01

    Full Text Available OBJECTIVE: To assess four different chemical surface conditioning methods for ceramic material before bracket bonding, and their impact on shear bond strength and surface integrity at debonding.METHODS: Four experimental groups (n = 13 were set up according to the ceramic conditioning method: G1 = 37% phosphoric acid etching followed by silane application; G2 = 37% liquid phosphoric acid etching, no rinsing, followed by silane application; G3 = 10% hydrofluoric acid etching alone; and G4 = 10% hydrofluoric acid etching followed by silane application. After surface conditioning, metal brackets were bonded to porcelain by means of the Transbond XP system (3M Unitek. Samples were submitted to shear bond strength tests in a universal testing machine and the surfaces were later assessed with a microscope under 8 X magnification. ANOVA/Tukey tests were performed to establish the difference between groups (α= 5%.RESULTS: The highest shear bond strength values were found in groups G3 and G4 (22.01 ± 2.15 MPa and 22.83 ± 3.32 Mpa, respectively, followed by G1 (16.42 ± 3.61 MPa and G2 (9.29 ± 1.95 MPa. As regards surface evaluation after bracket debonding, the use of liquid phosphoric acid followed by silane application (G2 produced the least damage to porcelain. When hydrofluoric acid and silane were applied, the risk of ceramic fracture increased.CONCLUSIONS: Acceptable levels of bond strength for clinical use were reached by all methods tested; however, liquid phosphoric acid etching followed by silane application (G2 resulted in the least damage to the ceramic surface.

  15. Structure and Chemical Bond of Thermoelectric Ce-Co-Sb Skutterudites

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The correlations among composition,structure,chemical bond and thermoelectric property of skutterudites CoSb3 and CeCo5Fe3Sb12 have been studied by using density function and discrete variation (DFT-DVM) method.Three models for this study were proposed and calculated by which the "rattling" pattern was described.Model 1 is with Ce in the center,model 2 is with Ce away the center and near to Sb,and model 3 is also with Ce away the center but near to Fe.The calculated results show that in model 3,the ionic bond is the strongest,but the covalent bond is the weakest.Due to the different changes between ionic and covalent bond,there is less difference in the stability among the models 1,2 and 3.Therefore,these different models can exist at the same time,or can translate from one to another more easily.In other words,the "rattling" pattern has taken place.Unfilled model of CoSb3,without Ce and Fe,is called model 4.The covalent bond of Co-Sb or Fe-Sb in models 1,2 and 3 is weaker than that of Co-Sb in model 4,as some electrical cloud of Sb takes part in the covalent bond of Ce-Sb in the filled models.The result is consistent with the experimental result that the thermal conductivity of CeCo5Fe3Sb12 is lower than that of CoSb3,and the thermoelectric property of CeCo5Fe3Sb12 is superior to that of CoSb3.

  16. Recovering Valuable Phosphates: Chemical Biotechnology as a Problem Solver for the Environment.

    Science.gov (United States)

    Heinzelmann, Elsbeth

    2015-01-01

    Researchers from the HES-SO Valais/Wallis have demonstrated how to extract phosphate from sewage sludge on the laboratory scale using renewable energy sources from a microbial fuel cell. The mobilized phosphate barely contains heavy metals and can be used to produce fertilizer of marketable quality. The necessary energy comes from a sewage treatment plant and causes no additional costs.

  17. Electronic Structure and Chemical Bond of Ti3SiC2 and Adding Al Element

    Institute of Scientific and Technical Information of China (English)

    MIN Xinmin; LU Ning; MEI Bingchu

    2006-01-01

    The relation among electronic structure, chemical bond and property of Ti3SiC2 and Al-doped was studied by density function and discrete variation (DFT-DVM) method. When Al element is added into Ti3SiC2, there is a less difference of ionic bond, which does not play a leading role to influent the properties. After adding Al, the covalent bond of Al and the near Ti becomes somewhat weaker, but the covalent bond of Al and the Si in the same layer is obviously stronger than that of Si and Si before adding. Therefore, in preparation of Ti3SiC2, adding a proper quantity of Al can promote the formation of Ti3SiC2. The density of state shows that there is a mixed conductor character in both of Ti3SiC2 and adding Al element. Ti3SiC2 is with more tendencies to form a semiconductor. The total density of state near Fermi lever after adding Al is larger than that before adding, so the electric conductivity may increase after adding Al.

  18. Hybrid density functional study on lattice vibration, thermodynamic properties, and chemical bonding of plutonium monocarbide

    Science.gov (United States)

    Rong, Yang; Bin, Tang; Tao, Gao; BingYun, Ao

    2016-06-01

    Hybrid density functional theory is employed to systematically investigate the structural, magnetic, vibrational, thermodynamic properties of plutonium monocarbide (PuC and PuC0.75). For comparison, the results obtained by DFT, DFT + U are also given. For PuC and PuC0.75, Fock-0.25 hybrid functional gives the best lattice constants and predicts the correct ground states of antiferromagnetic (AFM) structure. The calculated phonon spectra suggest that PuC and PuC0.75 are dynamically stable. Values of the Helmholtz free energy ΔF, internal energy ΔE, entropy S, and constant-volume specific heat C v of PuC and PuC0.75 are given. The results are in good agreement with available experimental or theoretical data. As for the chemical bonding nature, the difference charge densities, the partial densities of states and the Bader charge analysis suggest that the Pu-C bonds of PuC and PuC0.75 have a mixture of covalent character and ionic character. The effect of carbon vacancy on the chemical bonding is also discussed in detail. We expect that our study can provide some useful reference for further experimental research on the phonon density of states, thermodynamic properties of the plutonium monocarbide. Project supported by the National Natural Science Foundation of China (Grant Nos. 21371160 and 21401173).

  19. Weak Intermolecular Hydrogen Bonds with Fluorine: Detection and Implications for Enzymatic/Chemical Reactions, Chemical Properties, and Ligand/Protein Fluorine NMR Screening.

    Science.gov (United States)

    Dalvit, Claudio; Vulpetti, Anna

    2016-05-23

    It is known that strong hydrogen-bonding interactions play an important role in many chemical and biological systems. However, weak or very weak hydrogen bonds, which are often difficult to detect and characterize, may also be relevant in many recognition and reaction processes. Fluorine serving as a hydrogen-bond acceptor has been the subject of many controversial discussions and there are different opinions about it. It now appears that there is compelling experimental evidence for the involvement of fluorine in weak intramolecular or intermolecular hydrogen bonds. Using established NMR methods, we have previously characterized and measured the strengths of intermolecular hydrogen-bond complexes involving the fluorine moieties CH2 F, CHF2 , and CF3 , and have compared them with the well-known hydrogen-bond complex formed between acetophenone and the strong hydrogen-bond donor p-fluorophenol. We now report evidence for the formation of hydrogen bonds involving fluorine with significantly weaker donors, namely 5-fluoroindole and water. A simple NMR method is proposed for the simultaneous measurement of the strengths of hydrogen bonds between an acceptor and a donor or water. Important implications of these results for enzymatic/chemical reactions involving fluorine, for chemical and physical properties, and for ligand/protein (19) F NMR screening are analyzed through experiments and theoretical simulations.

  20. Effects of sandblasting, H2SO4/HCl etching, and phosphate primer application on bond strength of veneering resin composite to commercially pure titanium grade 4.

    Science.gov (United States)

    Egoshi, Takafumi; Taira, Yohsuke; Soeno, Kohyoh; Sawase, Takashi

    2013-01-01

    This study investigated the effects of surface treatments on the bond strength of a resin composite to a commercially pure titanium. The bonding surfaces of all titanium specimens were ground with 1,000-grit silicon carbide paper and then subjected to one or more of these surface treatments: sandblasting with alumina (sand), etching with 45wt% H2SO4 and 15wt% HCl (SH-etchant) at 70°C for 10 min, and/or phosphate primer (MDP-primer) application. Specimens not subjected to any surface treatment were used as controls. After resin composite veneer placement and 24-h water immersion, the shear bond strengths of the specimens in descending order were: sand/SH-etchant/MDP-primer, sand/SH-etchant/no primer, no sand/SH-etchant/MDP-primer, sand/no etch/MDP-primer, no sand/SH-etchant/no primer, sand/no etch/no primer, no sand/no etch/MDP-primer, no sand/no etch/no primer. Scanning electron microscope observations revealed that sandblasting and SH-etchant created many micro- and nanoscale cavities on the titanium surface. Results showed that a combined use of sandblasting, SH-etchant, and MDP-primer application had a cooperative effect on titanium bonding.

  1. Synthesis of chemically bonded graphene/carbon nanotube composites and their application in large volumetric capacitance supercapacitors.

    Science.gov (United States)

    Jung, Naeyoung; Kwon, Soongeun; Lee, Dongwook; Yoon, Dong-Myung; Park, Young Min; Benayad, Anass; Choi, Jae-Young; Park, Jong Se

    2013-12-17

    Chemically bonded graphene/carbon nanotube composites as flexible supercapacitor electrode materials are synthesized by amide bonding. Carbon nanotubes attached along the edges and onto the surface of graphene act as spacers to increase the electrolyte-accessible surface area. Our lamellar structure electrodes demonstrate the largest volumetric capacitance (165 F cm(-3) ) ever shown by carbon-based electrodes.

  2. YNi and its hydrides: Phase stabilities, electronic structures and chemical bonding properties from first principles

    Energy Technology Data Exchange (ETDEWEB)

    Matar, S.F., E-mail: matar@icmcb-bordeaux.cnrs.fr [CNRS, Universite de Bordeaux, ICMCB, 87 avenue du Docteur Albert Schweitzer, F-33608 Pessac (France); Nakhl, M. [Universite Libanaise, Laboratoire de Chimie-Physique des Materiaux LCPM, Fanar (Lebanon); Al Alam, A.F.; Ouaini, N. [Universite Saint-Esprit de Kaslik, Faculte des Sciences et de Genie Informatique, Jounieh (Lebanon); Chevalier, B. [CNRS, Universite de Bordeaux, ICMCB, 87 avenue du Docteur Albert Schweitzer, F-33608 Pessac (France)

    2010-11-25

    Graphical abstract: Base centered orthorhombic YNiH{sub X} structure. For x = 3, only H1 and H2 are present. Highest hydrogen content YNiH{sub 4} is obtained when H3 are added. - Abstract: Within density functional theory, establishing the equations of states of YNi in two different controversial structures in the literature, leads to determine the orthorhombic FeB-type as the ground state one with small energy difference. For YNiH{sub 3} and YNiH{sub 4} hydrides crystallizing in the orthorhombic CrB-type structure the geometry optimization and the ab initio determination of the H atomic positions show that the stability of hydrogen decreases from the tri- to the tetra- hydride. New states brought by hydrogen within the valence band lead to its broadening and to enhanced localization of metal density of states. The chemical bonding analysis shows a preferential Ni-H bonding versus Y-H.

  3. LOBSTER: A tool to extract chemical bonding from plane-wave based DFT.

    Science.gov (United States)

    Maintz, Stefan; Deringer, Volker L; Tchougréeff, Andrei L; Dronskowski, Richard

    2016-04-30

    The computer program LOBSTER (Local Orbital Basis Suite Towards Electronic-Structure Reconstruction) enables chemical-bonding analysis based on periodic plane-wave (PAW) density-functional theory (DFT) output and is applicable to a wide range of first-principles simulations in solid-state and materials chemistry. LOBSTER incorporates analytic projection routines described previously in this very journal [J. Comput. Chem. 2013, 34, 2557] and offers improved functionality. It calculates, among others, atom-projected densities of states (pDOS), projected crystal orbital Hamilton population (pCOHP) curves, and the recently introduced bond-weighted distribution function (BWDF). The software is offered free-of-charge for non-commercial research. © 2016 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.

  4. Electronic Structures and Chemical Bonds of Cobaltite and Ni-Doped

    Institute of Scientific and Technical Information of China (English)

    MIN Xinmin; XING Xueling; ZHU Lei

    2005-01-01

    The relation among electronic structure, chemical bond and thermoelectric property of Ca3 Co2 O6 and Ni-doped was studied by density function theory and discrete variation method(DFT-DVM). The results indicate that the highest valence band (HVB) and the lowest conduction band(LCB) are mainly attributed to Co3 d, Ni3 d and O2 p atomic orbitals. The property of a semiconductor is shown from the gap between HVB and LCB. The gap of Ni-doped one is less than that of Ca3 Co2 O6. The non-metal bond or ceramic characteristic of Ni-doped one is weaker than that of Ca3 Co2 O6, but the metal characteristics of Ni-doped one are stronger than those of Ca3 Co2O6. The thermoelectric property should be improved by adding Ni element into the system of Ca3 Co2 O6.

  5. Palladium on Layered Double Hydroxide: A Heterogeneous System for the Enol Phosphate Carbon-Oxygen Bond Activation in Aqueous Media

    Directory of Open Access Journals (Sweden)

    Jaqueline D. Senra

    2017-01-01

    Full Text Available In this work, a new catalytic approach for the C-O activation of enol phosphates based on a palladium supported on layered double hydroxide was developed. In this case, two different ketene aminal phosphates were used as models to study the synthesis of α-phenyl enecarbamates N-Boc/CBz under the Suzuki-Miyaura conditions. The use of an ortho-bromoaniline as precursor allowed the synthesis of the 2-phenyl indole through an arylation/Heck cyclization. Catalyst reusability enabled the synthesis of the heterocycle in moderate yields for four consecutive runs.

  6. Atom-specific look at the surface chemical bond using x-ray emission spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Nilsson, A.; Wassdahl, N.; Weinelt, M. [Uppsala Univ. (Sweden)] [and others

    1997-04-01

    CO and N{sub 2} adsorbed on the late transition metals have become prototype systems regarding the general understanding of molecular adsorption. It is in general assumed that the bonding of molecules to transition metals can be explained in terms of the interaction of the frontier HOMO and LUMO molecular orbitals with the d-orbitals. In such a picture the other molecular orbitals should remain essentially the same as in the free molecule. For the adsorption of the isoelectronic molecules CO and N{sub 2} this has led to the so called Blyholder model i.e., a synergetic {sigma} (HOMO) donor and {pi} (LUMO) backdonation bond. The authors results at the ALS show that such a picture is oversimplified. The direct observation and identification of the states related to the surface chemical bond is an experimental challenge. For noble and transition metal surfaces, the adsorption induced states overlap with the metal d valence band. Their signature is therefore often obscured by bulk substrate states. This complication has made it difficult for techniques such as photoemission and inverse photoemission to provide reliable information on the energy of chemisorption induced states and has left questions unanswered regarding the validity of the frontier orbitals concept. Here the authors show how x-ray emission spectroscopy (XES), in spite of its inherent bulk sensitivity, can be used to investigate adsorbed molecules. Due to the localization of the core-excited intermediate state, XE spectroscopy allows an atomic specific separation of the valence electronic states. Thus the molecular contributions to the surface measurements make it possible to determine the symmetry of the molecular states, i.e., the separation of {pi} and {sigma} type states. In all the authors can obtain an atomic view of the electronic states involved in the formation of the chemical bond to the surface.

  7. Heteromolecular metal–organic interfaces: Electronic and structural fingerprints of chemical bonding

    Energy Technology Data Exchange (ETDEWEB)

    Stadtmüller, Benjamin; Schröder, Sonja [Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich GmbH, D-52425 Jülich (Germany); Jülich-Aachen Research Alliance (JARA) – Fundamentals of Future Information Technology, 52425 Jülich (Germany); Kumpf, Christian, E-mail: c.kumpf@fz-juelich.de [Peter Grünberg Institut (PGI-3), Forschungszentrum Jülich GmbH, D-52425 Jülich (Germany); Jülich-Aachen Research Alliance (JARA) – Fundamentals of Future Information Technology, 52425 Jülich (Germany)

    2015-10-01

    Highlights: • We present a study of molecular donor–acceptor blends adsorbed on Ag(1 1 1). • Geometric and electronic structure of blends and pristine phases are compared. • The surface bonding of the acceptor is strengthened, that of the donor weakened. • But counter intuitively, the acceptor (donor) bond length becomes larger (smaller). • This contradiction is resolved by a model based on charge transfer via the surface. - Abstract: Beside the fact that they attract highest interest in the field of organic electronics, heteromolecular structures adsorbed on metal surfaces, in particular donor–acceptor blends, became a popular field in fundamental science, possibly since some surprising and unexpected behaviors were found for such systems. One is the apparent breaking of a rather fundamental rule in chemistry, namely that stronger chemical bonds go along with shorter bond lengths, as it is, e.g., well-known for the sequence from single to triple bonds. In this review we summarize the results of heteromolecular monolayer structures adsorbed on Ag(1 1 1), which – regarding this rule – behave in a counterintuitive way. The charge acceptor moves away from the substrate while its electronic structure indicates a stronger chemical interaction, indicated by a shift of the formerly lowest unoccupied molecular orbital toward higher binding energies. The donor behaves in the opposite way, it gives away charge, hence, electronically the bonding to the surface becomes weaker, but at the same time it also approaches the surface. It looks as if the concordant link between electronic and geometric structure was broken. But both effects can be explained by a substrate-mediated charge transfer from the donor to the acceptor. The charge reorganization going along with this transfer is responsible for both, the lifting-up of the acceptor molecule and the filling of its LUMO, and also for the reversed effects at the donor molecules. In the end, both molecules

  8. An unexpected bridge between chemical bonding indicators and electrical conductivity through the localization tensor.

    Science.gov (United States)

    Pendás, Ángel Martín; Guevara-Vela, José Manuel; Crespo, Daniel Menéndez; Costales, Aurora; Francisco, Evelio

    2017-01-18

    While the modern theory of the insulating state shows that the conducting or insulating properties of a system can be extracted solely from the ground state properties via the so-called localization tensor (LT), no chemical reading of this important quantity has ever been offered. Here, a remarkable link between the LT and the bond orders as described by the delocalization indices (DIs) of chemical bonding theory is reported. This is achieved through a real space partition of the LT into intra- and interatomic contributions. We show that the convergence or divergence of the LT in the thermodynamic limit, which signals the insulating or conducting nature of an extended system, respectively, can be nailed down to DIs. This allows for the exploitation of traditional chemical intuition to identify essential and spectator atomic groups in determining electrical conductivity. The thermodynamic limit of the LT is controlled by the spatial decay rate of the interatomic DIs, exponential in insulators and power-law in conductors. Computational data of a few selected toy systems corroborate our results.

  9. A constitutive model for bonded geomaterials subject to mechanical and/or chemical degradation

    Science.gov (United States)

    Nova, R.; Castellanza, R.; Tamagnini, C.

    2003-08-01

    The mechanical behaviour of bonded geomaterials is described by means of an elastoplastic strain-hardening model. The internal variables, taking into account the history of the material, depend on the plastic strains experienced and on a conveniently defined scalar measure of damage induced by weathering and/or chemical degradation.For the sake of simplicity, it is assumed that only internal variables are affected by mechanical and chemical history of the material. Despite this simplifying assumption, it can be shown that many interesting phenomena exhibited by weathered bonded geomaterials can be successfully described. For instance, (i) the transition from brittle to ductile behaviour with increasing pressure of a calcarenite with collapsing internal structure, (ii) the complex behaviour of chalk and other calcareous materials in oedometric tests, (iii) the chemically induced variation of the stress and strain state of such kind of materials, are all phenomena that can be qualitatively reproduced. Several comparisons with experimental data show that the model can capture the observed behaviour also quantitatively.

  10. Chemical Hypoxia Brings to Light Altered Autocrine Sphingosine-1-Phosphate Signalling in Rheumatoid Arthritis Synovial Fibroblasts

    Directory of Open Access Journals (Sweden)

    Chenqi Zhao

    2015-01-01

    Full Text Available Emerging evidence suggests a role for sphingosine-1-phosphate (S1P in various aspects of rheumatoid arthritis (RA pathogenesis. In this study we compared the effect of chemical hypoxia induced by cobalt chloride (CoCl2 on the expression of S1P metabolic enzymes and cytokine/chemokine secretion in normal fibroblast-like synoviocytes (FLS and RAFLS. RAFLS incubated with CoCl2, but not S1P, produced less IL-8 and MCP-1 than normal FLS. Furthermore, incubation with the S1P2 and S1P3 receptor antagonists, JTE-013 and CAY10444, reduced CoCl2-mediated chemokine production in normal FLS but not in RAFLS. RAFLS showed lower levels of intracellular S1P and enhanced mRNA expression of S1P phosphatase 1 (SGPP1 and S1P lyase (SPL, the enzymes that are involved in intracellular S1P degradation, when compared to normal FLS. Incubation with CoCl2 decreased SGPP1 mRNA and protein and SPL mRNA as well. Inhibition of SPL enhanced CoCl2-mediated cytokine/chemokine release and restored autocrine activation of S1P2 and S1P3 receptors in RAFLS. The results suggest that the sphingolipid pathway regulating the intracellular levels of S1P is dysregulated in RAFLS and has a significant impact on cell autocrine activation by S1P. Altered sphingolipid metabolism in FLS from patients with advanced RA raises the issue of synovial cell burnout due to chronic inflammation.

  11. Peptide Bond Synthesis by a Mechanism Involving an Enzymatic Reaction and a Subsequent Chemical Reaction.

    Science.gov (United States)

    Abe, Tomoko; Hashimoto, Yoshiteru; Zhuang, Ye; Ge, Yin; Kumano, Takuto; Kobayashi, Michihiko

    2016-01-22

    We recently reported that an amide bond is unexpectedly formed by an acyl-CoA synthetase (which catalyzes the formation of a carbon-sulfur bond) when a suitable acid and l-cysteine are used as substrates. DltA, which is homologous to the adenylation domain of nonribosomal peptide synthetase, belongs to the same superfamily of adenylate-forming enzymes, which includes many kinds of enzymes, including the acyl-CoA synthetases. Here, we demonstrate that DltA synthesizes not only N-(d-alanyl)-l-cysteine (a dipeptide) but also various oligopeptides. We propose that this enzyme catalyzes peptide synthesis by the following unprecedented mechanism: (i) the formation of S-acyl-l-cysteine as an intermediate via its "enzymatic activity" and (ii) subsequent "chemical" S → N acyl transfer in the intermediate, resulting in peptide formation. Step ii is identical to the corresponding reaction in native chemical ligation, a method of chemical peptide synthesis, whereas step i is not. To the best of our knowledge, our discovery of this peptide synthesis mechanism involving an enzymatic reaction and a subsequent chemical reaction is the first such one to be reported. This new process yields peptides without the use of a thioesterified fragment, which is required in native chemical ligation. Together with these findings, the same mechanism-dependent formation of N-acyl compounds by other members of the above-mentioned superfamily demonstrated that all members most likely form peptide/amide compounds by using this novel mechanism. Each member enzyme acts on a specific substrate; thus, not only the corresponding peptides but also new types of amide compounds can be formed.

  12. ELECTRONIC AND CHEMICAL PROPERTIES OF PD IN BIMETALLIC SYSTEMS: HOW MUCH DO WE KNOW ABOUT HETERONUCLEAR METAL-METAL BONDING?

    Energy Technology Data Exchange (ETDEWEB)

    RODRIGUEZ,J.A.

    2001-09-27

    The experimental and theoretical studies described above illustrate the complex nature of the heteronuclear metal-metal bond. In many cases, bimetallic bonding induces a significant redistribution of charge around the bonded metals. This redistribution of charge is usually linked to the strength of the bimetallic bond, affects the position of the core and valence levels of the metals, and can determine the chemical reactivity of the system under study. New concepts are emerging [22,23,34,36] and eventually the coupling of experiment and theory can be useful for designing more efficient bimetallic catalysts [98,106,107].

  13. Radiological, chemical and morphological characterizations of phosphate rock and phosphogypsum from phosphoric acid factories in SW Spain

    Energy Technology Data Exchange (ETDEWEB)

    Renteria-Villalobos, Marusia, E-mail: marusia@us.es [Applied Nuclear Physics Group, University of Seville, ETS Arquitectura, Departamento de Fisica Aplicada, Avda. Reina Mercedes s/n, 41012 Seville (Spain); Advanced Materials Research Center (CIMAV), Miguel de Cervantes 120, 31109 Chihuahua (Mexico); Vioque, Ignacio, E-mail: ivioque@us.es [Applied Nuclear Physics Group, University of Seville, ETS Arquitectura, Departamento de Fisica Aplicada, Avda. Reina Mercedes s/n, 41012 Seville (Spain); Mantero, Juan, E-mail: manter@us.es [Applied Nuclear Physics Group, University of Seville, ETS Arquitectura, Departamento de Fisica Aplicada, Avda. Reina Mercedes s/n, 41012 Seville (Spain); Manjon, Guillermo, E-mail: manjon@us.es [Applied Nuclear Physics Group, University of Seville, ETS Arquitectura, Departamento de Fisica Aplicada, Avda. Reina Mercedes s/n, 41012 Seville (Spain)

    2010-09-15

    In this work, radiological, chemical, and also morphological characterization was performed in phosphate rock and phosphogypsum samples, in order to understand the behavior of toxic elements. Characterization was carried out using X-ray diffraction (XRD), X-ray fluorescence (XRF), gamma spectrometry and scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). Our results show that the phosphate rock was mainly composed of fluorapatite, calcite, perovskite, quartz, magnetite, pyrite and kaolinite, whereas phosphogypsum only exhibited dihydrated calcium sulfate. The activity concentration of U-series radioisotopes in phosphate rock was around 1640 Bq/kg. {sup 226}Ra and {sup 210}Pb tend to be distributed into phosphogypsum by up to 80%, whereas the fraction of U-isotopes is 10%. The most abundant trace elements in phosphate rock were Sr, Cr, V, Zn, Y, Ni and Ba. Some elements, such as Ba, Cd, Cu, La, Pb, Se, Sr, Th and Y, were enriched in the phosphogypsum. This enrichment may be attributed to an additional input associated to the sulfuric acid used for the phosphoric acid production. Furthermore, results from SEM-EDX demonstrated that toxic elements are not distributed homogeneously into phosphogypsum. Most of these elements are concentrated in particles <20 {mu}m of high porosity, and could be easily mobilized by leaching and/or erosion.

  14. Radiological, chemical and morphological characterizations of phosphate rock and phosphogypsum from phosphoric acid factories in SW Spain.

    Science.gov (United States)

    Rentería-Villalobos, Marusia; Vioque, Ignacio; Mantero, Juan; Manjón, Guillermo

    2010-09-15

    In this work, radiological, chemical, and also morphological characterization was performed in phosphate rock and phosphogypsum samples, in order to understand the behavior of toxic elements. Characterization was carried out using X-ray diffraction (XRD), X-ray fluorescence (XRF), gamma spectrometry and scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). Our results show that the phosphate rock was mainly composed of fluorapatite, calcite, perovskite, quartz, magnetite, pyrite and kaolinite, whereas phosphogypsum only exhibited dihydrated calcium sulfate. The activity concentration of U-series radioisotopes in phosphate rock was around 1640 Bq/kg. (226)Ra and (210)Pb tend to be distributed into phosphogypsum by up to 80%, whereas the fraction of U-isotopes is 10%. The most abundant trace elements in phosphate rock were Sr, Cr, V, Zn, Y, Ni and Ba. Some elements, such as Ba, Cd, Cu, La, Pb, Se, Sr, Th and Y, were enriched in the phosphogypsum. This enrichment may be attributed to an additional input associated to the sulfuric acid used for the phosphoric acid production. Furthermore, results from SEM-EDX demonstrated that toxic elements are not distributed homogeneously into phosphogypsum. Most of these elements are concentrated in particles <20 microm of high porosity, and could be easily mobilized by leaching and/or erosion.

  15. Quantum chemical calculations of bond dissociation energies for COOH scission and electronic structure in some acids

    Institute of Scientific and Technical Information of China (English)

    Zeng Hui; Zhao Jun; Xiao Xun

    2013-01-01

    Quantum chemical calculations are performed to investigate the equilibrium C-COOH bond distances and the bond dissociation energies (BDEs) for 15 acids.These compounds are studied by utilizing the hybrid density functional theory (DFT) (B3LYP,B3PW91,B3P86,PBE1PBE) and the complete basis set (CBS-Q) method in conjunction with the 6-31 lG** basis as DFT methods have been found to have low basis sets sensitivity for small and medium molecules in our previous work.Comparisons between the computational results and the experimental values reveal that CBS-Q method,which can produce reasonable BDEs for some systems in our previous work,seems unable to predict accurate BDEs here.However,the B3P86 calculated results accord very well with the experimental values,within an average absolute error of 2.3 kcal/mol.Thus,B3P86 method is suitable for computing the reliable BDEs of C-COOH bond for carboxylic acid compounds.In addition,the energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of studied compounds are estimated,based on which the relative thermal stabilities of the studied acids are also discussed.

  16. Trigermanides AEGe{sub 3} (AE = Ca, Sr, Ba). Chemical bonding and superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Castillo, Rodrigo; Schnelle, Walter; Baranov, Alexey I.; Burkhardt, Ulrich; Bobnar, Matej; Cardoso-Gil, Raul; Schwarz, Ulrich; Grin, Yuri [Max-Planck-Institut fuer Chemische Physik Fester Stoffe, Dresden (Germany)

    2016-08-01

    The crystal structures of the trigermanides AEGe{sub 3}(tI32) (AE = Ca, Sr, Ba; space group I4/mmm, for SrGe{sub 3}: a = 7.7873(1), c = 12.0622(3) Aa) comprise Ge{sub 2} dumbbells forming layered Ge substructures which enclose embedded AE atoms. The chemical bonding analysis by application of the electron localizability approach reveals a substantial charge transfer from the AE atoms to the germanium substructure. The bonding within the dumbbells is of the covalent two-center type. A detailed analysis of SrGe{sub 3} reveals that the interaction on the bond-opposite side of the Ge{sub 2} groups is not lone pair-like - as it would be expected from the Zintl-like interpretation of the crystal structure with anionic Ge layers separated by alkaline-earth cations - but multi-center strongly polar between the Ge{sub 2} dumbbells and the adjacent metal atoms. Similar atomic interactions are present in CaGe{sub 3} and BaGe{sub 3}. The variation of the alkaline-earth metal has a merely insignificant influence on the superconducting transition temperatures in the s,p-electron compounds AEGe{sub 3}.

  17. Ferroelectric phase transition in hydrogen-bonded 2-aminopyridine phosphate (NC sub 4 H sub 4 NH sub 2)centre dot H sub 3 PO sub 4

    CERN Document Server

    Czapla, Z; Waskowska, A

    2003-01-01

    A new crystal of 2-aminopyridine phosphate (NC sub 4 H sub 4 NH sub 2)centre dot H sub 3 PO sub 4 has been grown and its x-ray structure and physical properties were studied. At room temperature the crystals are monoclinic, space group C2/c. The flat 2-aminopyridine cations are hydrogen bonded to the anionic [PO sub 4 ] groups. The interesting feature of the crystal structure is the three-dimensional network of hydrogen bonds including, among others, two strong, symmetrical O centre dot centre dot centre dot H, H centre dot centre dot centre dot O interactions with disordered proton locations. Symmetrically related PO sub 4 anions linked through these protons form infinite (PO sub 4) subinfinity chains along the crystal a-axis. The anomalies in the temperature dependence of the electric permittivity showed that the crystal undergoes ferroelectric phase transition at T sub c = 103.5 K. The spontaneous polarization takes place along the crystal a-axis, being parallel to the chains of the hydrogen-bonded PO sub ...

  18. Effect of the application of a casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste and adhesive systems on bond durability of a fissure sealant.

    Science.gov (United States)

    Borges, Boniek Castillo Dutra; Catelan, Anderson; Sasaki, Robson Tetsuo; Ambrosano, Gláucia Maria Bovi; Reis, André Figueiredo; Aguiar, Flávio Henrique Baggio

    2013-01-01

    This study aimed to evaluate the effect of the previous application of a casein phosphopeptide-amorphous calcium phosphate paste (MI Paste, MI) and adhesive systems on the bond durability of a fissure sealant. Ninety-eight enamel blocks were obtained from proximal surfaces of erupted third molars. Specimens were divided into 14 groups (n = 7) according to the previous application of MI (with and without) and the adhesive systems used (no adhesive system; hydrophobic resin of a three-step etch-and-rinse adhesive system; etch-and-rinse single-bottle adhesive system; all-in-one adhesive system; two-step self-etching adhesive system; additional phosphoric acid conditioning and all-in-one adhesive system; additional phosphoric acid conditioning and two-step self-etching adhesive system). A fissure sealant (Fluroshield) was applied and photoactivated for 20 s. Beams (~0.7 mm(2)) were prepared for the microtensile bond strength test, which was executed after 24 h or 6 months of water storage. Fractured specimens were analyzed by scanning electronic microscopy. Data were analyzed by two-way ANOVA with repeated measures/Tukey's test (P adhesive systems presented higher means than those groups where MI was not applied. Higher frequency of cohesive failures was observed for groups with MI. Applying a CPP-ACP containing paste on enamel before adhesive systems was an effective method to increase bond durability of the sealant tested.

  19. Antibacterial polyetheretherketone implants immobilized with silver ions based on chelate-bonding ability of inositol phosphate: processing, material characterization, cytotoxicity, and antibacterial properties.

    Science.gov (United States)

    Kakinuma, H; Ishii, K; Ishihama, H; Honda, M; Toyama, Y; Matsumoto, M; Aizawa, M

    2015-01-01

    We developed a novel antibacterial implant by forming a hydroxyapatite (HAp) film on polyetheretherketone (PEEK) substrate, and then immobilizing silver ions (Ag(+) ) on the HAp film based on the chelate-bonding ability of inositol phosphate (IP6). First, the PEEK surface was modified by immersion into concentrated sulfuric acid for 10 min. HAp film was formed on the acid-treated PEEK via the soft-solution process using simulated body fluid (SBF), urea, and urease. After HAp coating, specimens were immersed into IP6 solution, and followed by immersion into silver nitrite solution at concentrations of 0, 0.5, 1, 5 or 10 mM. Ag(+) ions were immobilized on the resulting HAp film due to the chelate-bonding ability of IP6. On cell-culture tests under indirect conditions by Transwell, MC3T3-E1 cells on the specimens derived from the 0.5 and 1 mM Ag(+) solutions showed high relative growth when compared with controls. Furthermore, on evaluation of antibacterial activity in halo test, elution of Ag(+) ions from Ag(+) -immobilized HAp film inhibited bacterial growth. Therefore, the above-mentioned results demonstrated that specimens had both biocompatibility and strong antibacterial activity. The present coating therefore provides bone bonding ability to the implant surface and prevents the formation of biofilms in the early postoperative period.

  20. Porcelain laminate veneer restorations bonded with a three-liquid silane bonding agent and a dual-activated luting composite.

    Science.gov (United States)

    Matsumura, Hideo; Aida, Yukiko; Ishikawa, Yumi; Tanoue, Naomi

    2006-12-01

    This clinical report describes the fabrication and bonding of porcelain laminate veneer restorations in a patient with anterior open spaces. Laminate veneer restorations made of feldspathic porcelain were etched with 5% hydrofluoric acid, rinsed under tap water, ultrasonically cleaned with methanol, and primed with a chemically activated three-liquid silane bonding agent (Clearfil Porcelain Bond). The enamel surfaces were etched with 40% phosphoric acid, rinsed with water, and primed with a two-liquid bonding agent (Clearfil New Bond) that contained a hydrophobic phosphate (10-methacryloyloxydecyl dihydrogen phosphate; MDP). The restorations were bonded with a dual-activated luting composite (Clapearl DC). The veneers have been functioning satisfactorily for an observation period of one year. Combined use of the Clearfil bonding agents and Clapearl DC luting composite is an alternative to conventional materials for seating porcelain laminate veneer restorations, although the system is inapplicable to dentin bonding.

  1. Experimental evidence of chemical components in the bonding of helium and neon with neutral molecules.

    Science.gov (United States)

    Cappelletti, David; Bartocci, Alessio; Grandinetti, Felice; Falcinelli, Stefano; Belpassi, Leonardo; Tarantelli, Francesco; Pirani, Fernando

    2015-04-13

    The complexes of helium and neon with gaseous neutral molecules are generally perceived to be van der Waals adducts held together by physical (non-covalent) forces, owing to the combination of size (exchange) repulsion with dispersion/induction attraction. Molecular beam experiments confirm that this is the case for He-CF4 , Ne-CF4 adducts, but revealed that the interaction of He and Ne with CCl4 features an appreciable contribution of chemical components that arise from the anisotropy of the electron density of CCl4 that enhances a charge transfer from Ng (Ng=He, Ne). These findings furnish a novel assay of the bonding capabilities of helium and neon, and invite to revisit the neutral complexes of these elements as systems of chemical relevance. The CCl4 -Ng are also peculiar examples of halogen bonds, a group of interactions of major current concern. Finally, this investigation is a prelude to the development of semi-empirical models for force fields aimed to the unified description of static and dynamical properties of systems of comparable or higher complexity.

  2. Chemically bonded phosphorus/graphene hybrid as a high performance anode for sodium-ion batteries.

    Science.gov (United States)

    Song, Jiangxuan; Yu, Zhaoxin; Gordin, Mikhail L; Hu, Shi; Yi, Ran; Tang, Duihai; Walter, Timothy; Regula, Michael; Choi, Daiwon; Li, Xiaolin; Manivannan, Ayyakkannu; Wang, Donghai

    2014-11-12

    Room temperature sodium-ion batteries are of great interest for high-energy-density energy storage systems because of low-cost and natural abundance of sodium. Here, we report a novel phosphorus/graphene nanosheet hybrid as a high performance anode for sodium-ion batteries through facile ball milling of red phosphorus and graphene stacks. The graphene stacks are mechanically exfoliated to nanosheets that chemically bond with the surfaces of phosphorus particles. This chemical bonding can facilitate robust and intimate contact between phosphorus and graphene nanosheets, and the graphene at the particle surfaces can help maintain electrical contact and stabilize the solid electrolyte interphase upon the large volume change of phosphorus during cycling. As a result, the phosphorus/graphene nanosheet hybrid nanostructured anode delivers a high reversible capacity of 2077 mAh/g with excellent cycling stability (1700 mAh/g after 60 cycles) and high Coulombic efficiency (>98%). This simple synthesis approach and unique nanostructure can potentially be applied to other phosphorus-based alloy anode materials for sodium-ion batteries.

  3. Load and Time Dependence of Interfacial Chemical Bond-Induced Friction at the Nanoscale

    Science.gov (United States)

    Tian, Kaiwen; Gosvami, Nitya N.; Goldsby, David L.; Liu, Yun; Szlufarska, Izabela; Carpick, Robert W.

    2017-02-01

    Rate and state friction (RSF) laws are widely used empirical relationships that describe the macroscale frictional behavior of a broad range of materials, including rocks found in the seismogenic zone of Earth's crust. A fundamental aspect of the RSF laws is frictional "aging," where friction increases with the time of stationary contact due to asperity creep and/or interfacial strengthening. Recent atomic force microscope (AFM) experiments and simulations found that nanoscale silica contacts exhibit aging due to the progressive formation of interfacial chemical bonds. The role of normal load (and, thus, normal stress) on this interfacial chemical bond-induced (ICBI) friction is predicted to be significant but has not been examined experimentally. Here, we show using AFM that, for nanoscale ICBI friction of silica-silica interfaces, aging (the difference between the maximum static friction and the kinetic friction) increases approximately linearly with the product of the normal load and the log of the hold time. This behavior is attributed to the approximately linear dependence of the contact area on the load in the positive load regime before significant wear occurs, as inferred from sliding friction measurements. This implies that the average pressure, and thus the average bond formation rate, is load independent within the accessible load range. We also consider a more accurate nonlinear model for the contact area, from which we extract the activation volume and the average stress-free energy barrier to the aging process. Our work provides an approach for studying the load and time dependence of contact aging at the nanoscale and further establishes RSF laws for nanoscale asperity contacts.

  4. The role of the chemical composition of monetite on the synthesis and properties of α-tricalcium phosphate.

    Science.gov (United States)

    Duncan, Jo; Macdonald, James F; Hanna, John V; Shirosaki, Yuki; Hayakawa, Satoshi; Osaka, Akiyoshi; Skakle, Janet M S; Gibson, Iain R

    2014-01-01

    There has been a resurgence of interest in alpha-tricalcium phosphate (α-TCP), with use in cements, polymer composites and in bi- and tri-phasic calcium phosphate bone grafts. The simplest and most established method for preparing α-TCP is the solid state reaction of monetite (CaHPO4) and calcium carbonate at high temperatures, followed by quenching. In this study, the effect of the chemical composition of reagents used in the synthesis of α-TCP on the local structure of the final product is reported and findings previously reported pertaining to the phase composition and stability are also corroborated. Chemical impurities in the monetite reagents were identified and could be correlated to the calcium phosphate products formed; magnesium impurities favoured the formation of β-TCP, whereas single phase α-TCP was favoured when magnesium levels were low. Monetite synthesised in-house exhibited a high level of chemical purity; when this source was used to produce an α-TCP sample, the α-polymorph could be obtained by both quenching and by cooling to room temperature in the furnace at rates between 1 and 10°C/min, thereby simplifying the synthesis process. It was only when impurities were minimised that the 12 phosphorus environments in the α-TCP structure could be resolved by (31)P nuclear magnetic resonance; samples containing chemical impurity showed differing degrees of line-broadening. Reagent purity should therefore be considered a priority when synthesising/characterising the α-polymorph of TCP.

  5. Application of chemical structure and bonding of actinide oxide materials for forensic science

    Energy Technology Data Exchange (ETDEWEB)

    Wilkerson, Marianne Perry [Los Alamos National Laboratory

    2010-01-01

    We are interested in applying our understanding of actinide chemical structure and bonding to broaden the suite of analytical tools available for nuclear forensic analyses. Uranium- and plutonium-oxide systems form under a variety of conditions, and these chemical species exhibit some of the most complex behavior of metal oxide systems known. No less intriguing is the ability of AnO{sub 2} (An: U, Pu) to form non-stoichiometric species described as AnO{sub 2+x}. Environmental studies have shown the value of utilizing the chemical signatures of these actinide oxide materials to understand transport following release into the environment. Chemical speciation of actinide-oxide samples may also provide clues as to the age, source, or process history of the material. The scientific challenge is to identify, measure and understand those aspects of speciation of actinide analytes that carry information about material origin and history most relevant to forensics. Here, we will describe our efforts in material synthesis and analytical methods development that we will use to provide the fundamental science to characterize actinide oxide molecular structures for forensic science. Structural properties and initial results to measure structural variability of uranium oxide samples using synchrotron-based X-ray Absorption Fine Structure will be discussed.

  6. The role of the chemical composition of monetite on the synthesis and properties of α-tricalcium phosphate

    Energy Technology Data Exchange (ETDEWEB)

    Duncan, Jo, E-mail: jo.duncan@abdn.ac.uk [Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE (United Kingdom); MacDonald, James F., E-mail: J.F.MacDonald@warwick.ac.uk [Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL (United Kingdom); Hanna, John V., E-mail: J.V.Hanna@warwick.ac.uk [Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL (United Kingdom); Shirosaki, Yuki, E-mail: yukis@cc.okayama-u.ac.jp [Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima, Kita-ku, Okayama 700-8530 (Japan); Hayakawa, Satoshi, E-mail: satoshi@cc.okayama-u.ac.jp [Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima, Kita-ku, Okayama 700-8530 (Japan); Osaka, Akiyoshi, E-mail: a-osaka@cc.okayama-u.ac.jp [Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima, Kita-ku, Okayama 700-8530 (Japan); Skakle, Janet M.S., E-mail: j.skakle@abdn.ac.uk [Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE (United Kingdom); Gibson, Iain R., E-mail: i.r.gibson@abdn.ac.uk [Department of Chemistry, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE (United Kingdom); School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD (United Kingdom)

    2014-01-01

    There has been a resurgence of interest in alpha-tricalcium phosphate (α-TCP), with use in cements, polymer composites and in bi- and tri-phasic calcium phosphate bone grafts. The simplest and most established method for preparing α-TCP is the solid state reaction of monetite (CaHPO{sub 4}) and calcium carbonate at high temperatures, followed by quenching. In this study, the effect of the chemical composition of reagents used in the synthesis of α-TCP on the local structure of the final product is reported and findings previously reported pertaining to the phase composition and stability are also corroborated. Chemical impurities in the monetite reagents were identified and could be correlated to the calcium phosphate products formed; magnesium impurities favoured the formation of β-TCP, whereas single phase α-TCP was favoured when magnesium levels were low. Monetite synthesised in-house exhibited a high level of chemical purity; when this source was used to produce an α-TCP sample, the α-polymorph could be obtained by both quenching and by cooling to room temperature in the furnace at rates between 1 and 10 °C/min, thereby simplifying the synthesis process. It was only when impurities were minimised that the 12 phosphorus environments in the α-TCP structure could be resolved by {sup 31}P nuclear magnetic resonance; samples containing chemical impurity showed differing degrees of line-broadening. Reagent purity should therefore be considered a priority when synthesising/characterising the α-polymorph of TCP. - Highlights: • Most commercial sources of monetite contain impurities that affect synthesis of phase pure α-TCP. • Ratio of α:β-TCP polymorphs formed by solid state reaction is dependent on reactant chemical purity. • If reagents in α-TCP synthesis are chemically pure, quenching is not required to obtain α-polymorph. • 12 unique P sites in α-TCP were only fully realised by {sup 31}P NMR when chemically pure reagents are used.

  7. Changes in soil toxicity by phosphate-aided soil washing: effect of soil characteristics, chemical forms of arsenic, and cations in washing solutions.

    Science.gov (United States)

    Jho, Eun Hea; Im, Jinwoo; Yang, Kyung; Kim, Young-Jin; Nam, Kyoungphile

    2015-01-01

    This study was set to investigate the changes in the toxicity of arsenic (As)-contaminated soils after washing with phosphate solutions. The soil samples collected from two locations (A: rice paddy and B: forest land) of a former smelter site were contaminated with a similar level of As. Soil washing (0.5 M phosphate solution for 2 h) removed 24.5% As, on average, in soil from both locations. Regardless of soil washing, Location A soil toxicities, determined using Microtox, were greater than that of Location B and this could be largely attributed to different soil particle size distribution. With soils from both locations, the changes in As chemical forms resulted in either similar or greater toxicities after washing. This emphasizes the importance of considering ecotoxicological aspects, which are likely to differ depending on soil particle size distribution and changes in As chemical forms, in addition to the total concentration based remedial goals, in producing ecotoxicologically-sound soils for reuse. In addition, calcium phosphate used as the washing solution seemed to contribute more on the toxic effects of the washed soils than potassium phosphate and ammonium phosphate. Therefore, it would be more appropriate to use potassium or ammonium phosphate than calcium phosphate for phosphate-aided soil washing of the As-contaminated soils.

  8. First principles study of the alloying effect on chemical bonding characteristics of helium in La-Ni-M tritides

    Energy Technology Data Exchange (ETDEWEB)

    Hu, C.H. [Institute of Metal Research, Chinese Academy of Science, 72 Wenhua Road, Shenyang 110016 (China); Zhang, R.J. [Institute of Metal Research, Chinese Academy of Science, 72 Wenhua Road, Shenyang 110016 (China); Shi, L.Q. [Applied Ion Bean Physics Laboratory, Fudan University, Shanghai 200433 (China); Chen, D.M. [Institute of Metal Research, Chinese Academy of Science, 72 Wenhua Road, Shenyang 110016 (China); Wang, Y.M. [Institute of Metal Research, Chinese Academy of Science, 72 Wenhua Road, Shenyang 110016 (China)]. E-mail: ymwang@imr.ac.cn; Yang, K. [Institute of Metal Research, Chinese Academy of Science, 72 Wenhua Road, Shenyang 110016 (China)

    2005-11-15

    The alloying effect on the electronic structure of La-Ni-M tritides is investigated using the first principles discrete variational X{alpha}(DV-X{alpha}) method. The calculated results show that the covalent interaction between atoms will play a much more important role in studying the alloying effect on chemical bonding characteristics in La-Ni-M tritides than ionic interaction. It is also found that in La-Ni-M tritides helium forms stronger covalent bonds with the weaker hydride forming elements than La. By analyzing the relation between the binding energy difference and bond order, our study indicates that after some alloying elements substituting for Ni locating in 3g site in tritides, the helium retention capability becomes stronger, changes as the following sequence: Al > Cr > Mn > Fe > Co > Ni, and is also very distinct for Cu although the chemical bonding between Cu atom and Ni atom is degraded drastically.

  9. Planar waveguides formed in a new chemically stable Er3+/Yb3+ co-doped phosphate glass

    Institute of Scientific and Technical Information of China (English)

    Shilong Zhao; Baoyu Chen; Junjiang Hu; Lili Hu

    2005-01-01

    @@ A new Er3+/Yb3+ co-doped phosphate glass has been prepared, which exhibits good chemical durability and spectral properties. Planar graded index waveguides have been fabricated in the glass by Ag+-Na+ ion exchange in a mixed melt of silver nitrate and potassium nitrate. Ion exchange is carried out by varying the process parameters such as temperature, diffusion time, and molten salt compositions. The diffusion parameters, diffusion coefficients, and activation energy are determined by the guidelines of fabricated waveguides, which are determined by the input prism coupling technique.

  10. Influence of chemical bonding of chlorides with aluminates in cement hidratation process on corrosion steel bars in concrete

    OpenAIRE

    2010-01-01

    The presence of chlorides in concrete is a permanent subject of research because they cause corrosion of steel bars. Chlorides added to the concrete during preparation, as accelerators of the bonding of cement minerals process, enter into reaction with aluminates, creating a phase known as chloroaluminate hydrates. In everyday conditions the product of chemical bonding between chlorides and aluminates is usually monochloridealuminate C3A·CaCl2·Hx, better known as Friedel's salt. In this paper...

  11. Chemical bonding in aqueous hexacyano cobaltate from photon- and electron-detection perspectives

    Science.gov (United States)

    Lalithambika, Sreeju Sreekantan Nair; Atak, Kaan; Seidel, Robert; Neubauer, Antje; Brandenburg, Tim; Xiao, Jie; Winter, Bernd; Aziz, Emad F.

    2017-01-01

    The electronic structure of the [Co(CN)6]3- complex dissolved in water is studied using X-ray spectroscopy techniques. By combining electron and photon detection methods from the solutions ionized or excited by soft X-rays we experimentally identify chemical bonding between the metal center and the CN ligand. Non-resonant photoelectron spectroscopy provides solute electron binding energies, and nitrogen 1 s and cobalt 2p resonant core-level photoelectron spectroscopy identifies overlap between metal and ligand orbitals. By probing resonances we are able to qualitatively determine the ligand versus metal character of the respective occupied and non-occupied orbitals, purely by experiment. For the same excitations we also detect the emitted X-rays, yielding the complementary resonant inelastic X-ray scattering spectra. For a quantitative interpretation of the spectra, we perform theoretical electronic-structure calculations. The latter provide both orbital energies and orbital character which are found to be in good agreement with experimental energies and with experimentally inferred orbital mixing. We also report calculated X-ray absorption spectra, which in conjunction with our orbital-structure analysis, enables us to quantify various bonding interactions with a particular focus on the water-solvent - ligand interaction and the strength of π-backbonding between metal and ligand.

  12. Chemical bonding and electronic-structure in MAX phases as viewed by X-ray spectroscopy and density functional theory

    Science.gov (United States)

    Magnuson, Martin; Mattesini, Maurizio

    2017-01-01

    This is a critical review of MAX-phase carbides and nitrides from an electronic-structure and chemical bonding perspective. This large group of nanolaminated materials is of great scientific and technological interest and exhibit a combination of metallic and ceramic features. These properties are related to the special crystal structure and bonding characteristics with alternating strong M-C bonds in high-density MC slabs, and relatively weak M-A bonds between the slabs. Here, we review the trend and relationship between the chemical bonding, conductivity, elastic and magnetic properties of the MAX phases in comparison to the parent binary MX compounds with the underlying electronic structure probed by polarized X-ray spectroscopy. Spectroscopic studies constitute important tests of the results of state-of-the-art electronic structure density functional theory that is extensively discussed and are generally consistent. By replacing the elements on the M, A, or X-sites in the crystal structure, the corresponding changes in the conductivity, elasticity, magnetism and other materials properties makes it possible to tailor the characteristics of this class of materials by controlling the strengths of their chemical bonds.

  13. Fabrication of a molecular-level multilayer film on organic polymer surfaces via chemical bonding assembly.

    Science.gov (United States)

    Zhao, Hongchi; Yang, Peng; Deng, Jianping; Liu, Lianying; Zhu, Jianwu; Sui, Yuan; Lu, Jiaoming; Yang, Wantai

    2007-02-13

    A fresh multilayer film was fabricated on a molecular level and successfully tethered to the surface of a hydroxylated organic substrate via chemical bonding assembly (CBA). Sulfate anion groups (SO4-) were preintroduced onto the surface of biaxially oriented polypropylene (BOPP) films via a reference method. Upon hydrolysis of the SO4- groups, hydroxyl groups (--OH) were formed that subsequently acted as initial reagents for a series of alternate reactions with terephthalyl chloride (TPC) and bisphenol A (BPA). A stable and well-defined multilayer film was thus fabricated via the CBA method. As a result of the nanoscale multilayer fresh film being abundant with reactive groups, it is believed that the film and its fabrication method should provide a fundamental platform for further surface functionalization and direct the design of advanced materials with desired properties.

  14. Intramolecular hydrogen bonding in myricetin and myricitrin. Quantum chemical calculations and vibrational spectroscopy

    Science.gov (United States)

    Vojta, Danijela; Dominković, Katarina; Miljanić, Snežana; Spanget-Larsen, Jens

    2017-03-01

    The molecular structures of myricetin (3,3‧,4‧,5,5‧,7-hexahydroxyflavone; MCE) and myricitrin (myricetin 3-O-rhamnoside; MCI) are investigated by quantum chemical calculations (B3LYP/6-311G**). Two preferred molecular rotamers of MCI are predicted, corresponding to different conformations of the O-rhamnoside subunit. The rotamers are characterized by different hydrogen bonded cross-links between the hydroxy groups of the rhamnoside substituent and the parent MCE moiety. The predicted OH stretching frequencies are compared with vibrational spectra of MCE and MCI recorded for the sake of this investigation (IR and Raman). In addition, a reassignment of the Cdbnd O stretching bands is suggested.

  15. Micro-chemical analysis of diffusion bonded W-SiC joint

    Energy Technology Data Exchange (ETDEWEB)

    Matsuo, Genichiro [Graduate Student, Graduate School of Engineering, Hokkaido University, Sapporo Hokkaido 060-8628 (Japan); Shibayama, Tamaki, E-mail: shiba@ufml.caret.hokudai.ac.jp [Center for Advanced Research of Energy Conversion Materials, Hokkaido University, Sapporo Hokkaido 060-8628 (Japan); Kishimoto, Hirotatsu [Department of Materials Science and Engineering, Muroran Institute of Technology, Muroran Hokkaido 050-8585 (Japan); Hamada, Kouichi; Watanabe, Seiichi [Center for Advanced Research of Energy Conversion Materials, Hokkaido University, Sapporo Hokkaido 060-8628 (Japan)

    2011-10-01

    W and SiC joining has an attractive feature for high-temperature energy conversion systems. However, it is unclear and that is necessary to study the microstructure of the reaction phase between W and SiC by using the thermal diffusion bonding method. This work demonstrates the strengthening mechanism of W and SiC joining through a microstructure analysis of the reaction phase by FE-TEM/EDS and the observation of the interface in W and SiC after the crack propagation in HVEM. The reaction phase was amorphous, with a gap from 500 to 600 nm between W and SiC. Fine precipitates with a diameter of several tens nanometer were formed in the reaction phase. The reaction phase and precipitates did not match the chemical composition of the equilibrium compound. It is conceivable that the reaction phase and precipitates exist as a non-equilibrium condition before they reach equilibrium condition.

  16. Chemical Bonding in Aqueous Ferrocyanide: Experimental and Theoretical X-ray Spectroscopic Study

    CERN Document Server

    Engel, Nicholas; Suljoti, Edlira; Garcia-Diez, Raul; Lange, Kathrin M; Atak, Kaan; Golnak, Ronny; Kothe, Alexander; Dantz, Marcus; Kühn, Oliver; Aziz, Emad F

    2013-01-01

    Resonant inelastic X-ray scattering (RIXS) and X-ray absorption (XA) experiments at the iron L- and nitrogen K-edge are combined with high-level first principles restricted active space self-consistent field (RASSCF) calculations for a systematic investigation of the nature of the chemical bond in potassium ferrocyanide in aqueous solution. The atom- and site-specific RIXS excitations allow for direct observation of ligand-to-metal (Fe L-edge) and metal-to-ligand (N K-edge) charge transfer bands and thereby evidence for strong {\\sigma}-donation and {\\pi}-back-donation. The effects are identified by comparing experimental and simulated spectra related to both the unoccupied and occupied molecular orbitals in solution.

  17. Effect of cross-linking with riboflavin and ultraviolet A on the chemical bonds and ultrastructure of human sclera

    Science.gov (United States)

    Jung, Gyeong-Bok; Lee, Hui-Jae; Kim, Ji-Hye; Lim, Jin Ik; Choi, Samjin; Jin, Kyung-Hyun; Park, Hun-Kuk

    2011-12-01

    This study examined the effect of the cross-linking with riboflavin-ultraviolet A (UVA) irradiation on the chemical bonds and ultrastructural changes of human sclera tissues using Raman spectroscopy and atomic force microscopy (AFM). Raman spectroscopy of the normal and cross-linked human sclera tissue revealed different types of the riboflavin-UVA and collagen interactions, which could be identified from their unique peaks, intensity, and shape. Raman spectroscopy can prove to be a powerful tool for examining the chemical bond of collagenous tissues at the molecular level. After riboflavin-UVA treatment, unlike a regular parallel arrangement of normal collagen fibrils, the AFM image revealed interlocking arrangements of collagen fibrils. The observed changes in the surface topography of the collagen fibrils, as well as in their chemical bonds in the sclera tissue, support the formation of interfibrilar cross-links in sclera tissues.

  18. Mechanical properties of chemically bonded sand core materials dipped in sol-gel coating impregnated with filter

    DEFF Research Database (Denmark)

    Nwaogu, Ugochukwu Chibuzoh; Tiedje, Niels Skat

    2012-01-01

    -displacement curve from which the mechanical properties of the materials are deduced. The fracture surfaces were examined using a stereomicroscope and a scanning electron microscope. From the results, the strengths of the core materials were slightly reduced by the coating in tensile and flexural modes, while...... the strengths were increased under compression. The mode of fracture of the chemically bonded sand core materials was observed to be intergranular through the binder. The stiffness of the chemically bonded sand core materials was determined. For better understanding of the mechanical properties......A novel sol-gel coating impregnated with filter dust was applied on chemically bonded sand core materials by dipping. After curing, the strengths of the core materials were measured under uniaxial loading using a new strength testing machine (STM). The STM presents the loading history as a force...

  19. Effect of several additives and their admixtures on the physico-chemical properties of a calcium phosphate cement.

    Science.gov (United States)

    Bohner, M; Merkle, H P; Landuyt, P V; Trophardy, G; Lemaitre, J

    2000-02-01

    Combinations of citrate (C6H5O(7)3-), pyrophosphate (P2O(7)4-) and sulfate (SO(4)2-) ions were used to modify the physico-chemical properties of a calcium phosphate cement (CPC) composed of beta-tricalcium phosphate (beta-TCP) and phosphoric acid (PA) solution. The results obtained with only one additive at a time are similar to those previously published. New facts are: the positive effect of C6H5O(7)3- ions on cement failure strain and their negative effect on cement pH. The position of the setting time maximum measured at an SO(4)2- concentration of 0.09 M was not displaced by the addition of C6H5O(7)3- and P2O(7)4- ions. However, the effect of SO(4)2- ions on the setting time was depressed by C6H5O(7)3- ions. Moreover, no increase in tensile strength was observed when increasing amounts of SO(4)2- were added into a C6H5O(7)3--containing cement. The latter results suggest a competitive effect of C6H5O(7)3- and SO(4)2- on setting time and tensile strength. Anhydrous dicalcium phosphate (DCP; CaHPO4) appeared in cement samples dried just after setting, but not in cement samples incubated for 24 h in deionized water before the drying step. It is believed that the setting reaction is stopped by the drying step, leaving a low internal pH in the sample, hence providing favorable conditions for the transformation of dicalcium phosphate dihydrate (DCPD) into DCP. Interestingly, even though C6H5O(7)3- ions dramatically lowered the equilibrium pH of the cement with 5 ml of deionized water, they still prevented the occurrence of the transformation of DCPD into DCP.

  20. Layer-by-layer fabrication of chemical-bonded graphene coating for solid-phase microextraction.

    Science.gov (United States)

    Zhang, Suling; Du, Zhuo; Li, Gongke

    2011-10-01

    A new fabrication strategy of the graphene-coated solid-phase microextraction (SPME) fiber is developed. Graphite oxide was first used as starting coating material that covalently bonded to the fused-silica substrate using 3-aminopropyltriethoxysilane (APTES) as cross-linking agent and subsequently deoxidized by hydrazine to give the graphene coating in situ. The chemical bonding between graphene and the silica fiber improve its chemical stability, and the obtained fiber was stable enough for more than 150 replicate extraction cycles. The graphene coating was wrinkled and folded, like the morphology of the rough tree bark. Its performance is tested by headspace (HS) SPME of polycyclic aromatic hydrocarbons (PAHs) followed by GC/MS analysis. The results showed that the graphene-coated fiber exhibited higher enrichment factors (EFs) from 2-fold for naphthalene to 17-fold for B(b)FL as compared to the commercial polydimethylsioxane (PDMS) fiber, and the EFs increased with the number of condensed rings of PAHs. The strong adsorption affinity was believed to be mostly due to the dominant role of π-π stacking interaction and hydrophobic effect, according to the results of selectivity study for a variety of organic compounds including PAHs, the aromatic compounds with different substituent groups, and some aliphatic hydrocarbons. For PAHs analysis, the graphene-coated fiber showed good precision (<11%), low detection limits (1.52-2.72 ng/L), and wide linearity (5-500 ng/L) under the optimized conditions. The repeatability of fiber-to-fiber was 4.0-10.8%. The method was applied to simultaneous analysis of eight PAHs with satisfactory recoveries, which were 84-102% for water samples and 72-95% for soil samples, respectively.

  1. X-ray photoelectron spectra structure and chemical bonding in AmO2

    Directory of Open Access Journals (Sweden)

    Teterin Yury A.

    2015-01-01

    Full Text Available Quantitative analysis was done of the X-ray photoelectron spectra structure in the binding energy range of 0 eV to ~35 eV for americium dioxide (AmO2 valence electrons. The binding energies and structure of the core electronic shells (~35 eV-1250 eV, as well as the relativistic discrete variation calculation results for the Am63O216 and AmO8 (D4h cluster reflecting Am close environment in AmO2 were taken into account. The experimental data show that the many-body effects and the multiplet splitting contribute to the spectral structure much less than the effects of formation of the outer (0-~15 eV binding energy and the inner (~15 eV-~35 eV binding energy valence molecular orbitals. The filled Am 5f electronic states were shown to form in the AmO2 valence band. The Am 6p electrons participate in formation of both the inner and the outer valence molecular orbitals (bands. The filled Am 6p3/2 and the O 2s electronic shells were found to make the largest contributions to the formation of the inner valence molecular orbitals. Contributions of electrons from different molecular orbitals to the chemical bond in the AmO8 cluster were evaluated. Composition and sequence order of molecular orbitals in the binding energy range 0-~35 eV in AmO2 were established. The experimental and theoretical data allowed a quantitative scheme of molecular orbitals for AmO2, which is fundamental for both understanding the chemical bond nature in americium dioxide and the interpretation of other X-ray spectra of AmO2.

  2. Anatomy of bond formation. Bond length dependence of the extent of electron sharing in chemical bonds from the analysis of domain-averaged Fermi holes.

    Science.gov (United States)

    Ponec, Robert; Cooper, David L

    2007-01-01

    We demonstrate that domain-average Fermi hole (DAFH) analysis, which has previously been used at the Hartree-Fock level, remains useful after the proper introduction of electron correlation. We perform a systematic investigation of the variation of the picture of bonding with increasing bond length in simple diatomic molecules such as N2 and LiH. Alongside values of a shared-electron distribution index (SEDI), this analysis provides further insight into the geometry dependence of the extent of electron sharing in polar and non-polar systems. We also use DAFH analysis, with correlated wave functions, to evaluate the (potential) multicentre bonding in the electron-deficient and electron-rich molecules CH2Li2 and CH2N2, respectively.

  3. Preparation, physical-chemical characterization, and cytocompatibility of polymeric calcium phosphate cements.

    Science.gov (United States)

    Khashaba, Rania M; Moussa, Mervet; Koch, Christopher; Jurgensen, Arthur R; Missimer, David M; Rutherford, Ronny L; Chutkan, Norman B; Borke, James L

    2011-01-01

    Aim. Physicochemical mechanical and in vitro biological properties of novel formulations of polymeric calcium phosphate cements (CPCs) were investigated. Methods. Monocalcium phosphate, calcium oxide, and synthetic hydroxyapatite were combined with either modified polyacrylic acid, light activated polyalkenoic acid, or polymethyl vinyl ether maleic acid to obtain Types I, II, and III CPCs. Setting time, compressive and diametral strength of CPCs was compared with zinc polycarboxylate cement (control). Specimens were characterized using X-ray diffraction, scanning electron microscopy, and infrared spectroscopy. In vitro cytotoxicity of CPCs and control was assessed. Results. X-ray diffraction analysis showed hydroxyapatite, monetite, and brushite. Acid-base reaction was confirmed by the appearance of stretching peaks in IR spectra of set cements. SEM revealed rod-like crystals and platy crystals. Setting time of cements was 5-12 min. Type III showed significantly higher strength values compared to control. Type III yielded high biocompatibility. Conclusions. Type III CPCs show promise for dental applications.

  4. Electronic properties and chemical bonding in quaternary arsenide oxides LaZnAsO and YZnAsO

    Energy Technology Data Exchange (ETDEWEB)

    Bannikov, V.V.; Shein, I.R. [Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, Pervomaiskaya, 91, 620041, Ekaterinburg (Russian Federation); Ivanovskii, A.L., E-mail: ivanovskii@ihim.uran.ru [Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, Pervomaiskaya, 91, 620041, Ekaterinburg (Russian Federation)

    2009-07-15

    First principles FLAPW-GGA band structure calculations are employed to obtain the structural, electronic properties and chemical bonding picture for two related phases, namely, quaternary arsenide oxides LaZnAsO and YZnAsO. These compounds are found to be direct-transition type semiconductors with the GGA gaps of about 0.65-1.30 eV. The peculiarities of chemical bonding in these phases are investigated and discussed in comparison with quaternary arsenide oxide LaFeAsO-a basic phase for the newly discovered 26-55 K superconductors.

  5. Synthesis of advanced chemically bonded ceramics for solidification of radioactive wastes

    Energy Technology Data Exchange (ETDEWEB)

    Seneda, Jose A.; Dellamano, Jose C.; Queiroz, Carlos A.S.; Genova, Luis A.; Rocha, Soraya M.R. da; Vicente, Roberto, E-mail: jaseneda@ipen.b, E-mail: jcdellam@ipen.b, E-mail: cqueiroz@ipen.b, E-mail: lgenova@ipen.b, E-mail: smrrocha@ipen.b, E-mail: rvicente@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    This paper presents the results of a preliminary study on the synthesis of advanced chemically bounded ceramics for use to immobilize radioactive wastes. A monolithic, crystalline, ceramic-like material, in the form of MgKPO{sub 4}.6H{sub 2}O, is obtained by reaction of magnesium oxide with potassium monophosphate, at room temperature. The thermodynamics of the reaction indicates the need of a previous treatment of the MgO above 1200 deg C to avoid the formation of magnesium phosphate salts, as revealed by thermogravimetric analysis and X-ray diffraction. The different crystalline phases and microstructure of reaction products are analyzed by X-ray diffraction and scanning electron microscopy, indicating that the material has the characteristics of a matrix for immobilization of radioactive waste. Results obtained thus far indicate the possibility of using this material to replace Portland cement in waste immobilization, offsetting the higher cost of raw material input with a larger fraction of waste in the waste form. More research on characterization of the waste form with mechanical strength tests of specimens incorporating varying waste compositions, and on the leaching potential of the material for a series of radioactive as well hazardous industrial wastes is being planned. (author)

  6. The nature of chemical bond in trioxide Mi-UO3

    Directory of Open Access Journals (Sweden)

    Teterin Yury A.

    2002-01-01

    Full Text Available Low-energy X-ray photoelectron and conversion electron spectra from uranium trioxide were measured, and calculations were done for the [UO2O4]-6 (D4b cluster which reflects the structure of uranium close environment in MI-UO3 in the non-relativistic and relativistic Xa-DVM approximation. This enabled a satisfactory qualitative and in some cases quantitative agreement between the experimental and theoretical data, and interpretation of such spectra. Despite the traditional opinion that before participation in the chemical binding, the U5f electrons could be promoted to the higher (for example - U6d levels, it was theoretically proved and experimentally confirmed that the U5f electrons (about two U5f electrons are able to participate directly in the chemical bond formation in uranium trioxide. The filled U5f states proved to be localized in the outer valence molecular orbitals energy range 4-9 eV, while the vacant U5f states were generally localized in the low-energy range (0-6 eV above zero. It was experimentally shown that U6p electrons not only participate effectively in the inner valence molecular orbital formation but also participate strongly (more than 1 U6p electron in the formation of die filled outer valence molecular orbitals.

  7. CHEMICAL ACTIVATION OF MOLECULES BY METALS: EXPERIMENTAL STUDIES OF ELECTRON DISTRIBUTIONS AND BONDING

    Energy Technology Data Exchange (ETDEWEB)

    LICHTENBERGER, DENNIS L.

    2002-03-26

    This research program is directed at obtaining detailed experimental information on the electronic interactions between metals and organic molecules. These interactions provide low energy pathways for many important chemical and catalytic processes. A major feature of the program is the continued development and application of our special high-resolution valence photoelectron spectroscopy (UPS), and high-precision X-ray core photoelectron spectroscopy (XPS) instrumentation for study of organometallic molecules in the gas phase. The study involves a systematic approach towards understanding the interactions and activation of bound carbonyls, C-H bonds, methylenes, vinylidenes, acetylides, alkenes, alkynes, carbenes, carbynes, alkylidenes, alkylidynes, and others with various monometal, dimetal, and cluster metal species. Supporting ligands include -aryls, alkoxides, oxides, and phosphines. We are expanding our studies of both early and late transition metal species and electron-rich and electron-poor environments in order to more completely understand the electronic factors that serve to stabilize particular organic fragments and intermediates on metals. Additional new directions for this program are being taken in ultra-high vacuum surface UPS, XPS, scanning tunneling microscopy (STM) and atomic force microscopy (AFM) experiments on both physisorbed and chemisorbed organometallic thin films. The combination of these methods provides additional electronic structure information on surface-molecule and molecule-molecule interactions. A very important general result emerging from this program is the identification of a close relationship between the ionization energies of the species and the thermodynamics of the chemical and catalytic reactions of these systems.

  8. Valence XPS structure and chemical bond in Cs2UO2Cl4

    Directory of Open Access Journals (Sweden)

    Teterin Yury A.

    2016-01-01

    Full Text Available Quantitative analysis was done of the valence electrons X-ray photoelectron spectra structure in the binding energy (BE range of 0 eV to ~35 eV for crystalline dicaesium tetrachloro-dioxouranium (VI (Cs2UO2Cl4. This compound contains the uranyl group UO2. The BE and structure of the core electronic shells (~35 eV-1250 eV, as well as the relativistic discrete variation calculation results for the UO2Cl4(D4h cluster reflecting U close environment in Cs2UO2Cl4 were taken into account. The experimental data show that many-body effects due to the presence of cesium and chlorine contribute to the outer valence (0-~15 eV BE spectral structure much less than to the inner valence (~15 eV-~35 eV BE one. The filled U5f electronic states were theoretically calculated and experimentally confirmed to be present in the valence band of Cs2UO2Cl4. It corroborates the suggestion on the direct participation of the U5f electrons in the chemical bond. Electrons of the U6p atomic orbitals participate in formation of both the inner (IVMO and the outer (OVMO valence molecular orbitals (bands. The filled U6p and the O2s, Cl3s electronic shells were found to make the largest contributions to the IVMO formation. The molecular orbitals composition and the sequence order in the binding energy range 0 eV-~35 eV in the UO2Cl4 cluster were established. The experimental and theoretical data allowed a quantitative molecular orbitals scheme for the UO2Cl4 cluster in the BE range 0-~35 eV, which is fundamental for both understanding the chemical bond nature in Cs2UO2Cl4 and the interpretation of other X-ray spectra of Cs2UO2Cl4. The contributions to the chemical binding for the UO2Cl4 cluster were evaluated to be: the OVMO contribution - 76%, and the IVMO contribution - 24 %.

  9. Electronic structure and chemical bond nature in Cs2PuO2Cl4

    Directory of Open Access Journals (Sweden)

    Teterin Yury A.

    2015-01-01

    Full Text Available X-ray photoelectron spectral analysis of dicaesiumtetrachlorodioxoplutonate (Cs2PuO2Cl4 single crystal was done in the binding energy range 0-~35 eV on the basis of binding energies and structure of the core electronic shells (~35 eV-1250 eV, as well as the relativistic discrete variation calculation results for the PuO2Cl4 (D4h. This cluster reflects Pu close environment in Cs2PuO2Cl4 containing the plutonyl group PuO2. The many-body effects due to the presence of cesium and chlorine were shown to contribute to the outer valence (0-~15 eV binding energy spectral structure much less than to the inner valence (~15 eV- ~35 eV binding energy one. The filled Pu 5f electronic states were theoretically calculated and experimentally con- firmed to present in the valence band of Cs2PuO2Cl4. It corroborates the suggestion on the direct participation of the Pu 5f electrons in the chemical bond. The Pu 6p atomic orbitals were shown to participate in formation of both the inner and the outer valence molecular orbitals (bands, while the filled Pu 6p and O 2s, Cl 3s electronic shells were found to take the largest part in formation of the inner valence molecular orbitals. The composition of molecular orbitals and the sequence order in the binding energy range 0-~35 eV in Cs2PuO2Cl4 were established. The quantitative scheme of molecular orbitals for Cs2PuO2Cl4 in the binding energy range 0-~15 eV was built on the basis of the experimental and theoretical data. It is fundamental for both understanding the chemical bond nature in Cs2PuO2Cl4 and the interpretation of other X-ray spectra of Cs2PuO2Cl4. The contributions to the chemical binding for the PuO2Cl4 cluster were evaluated to be: the contribution of the outer valence molecular orbitals -66 %, the contribution of the inner valence molecular orbitals -34 %.

  10. Understanding boron through size-selected clusters: structure, chemical bonding, and fluxionality.

    Science.gov (United States)

    Sergeeva, Alina P; Popov, Ivan A; Piazza, Zachary A; Li, Wei-Li; Romanescu, Constantin; Wang, Lai-Sheng; Boldyrev, Alexander I

    2014-04-15

    Boron is an interesting element with unusual polymorphism. While three-dimensional (3D) structural motifs are prevalent in bulk boron, atomic boron clusters are found to have planar or quasi-planar structures, stabilized by localized two-center-two-electron (2c-2e) σ bonds on the periphery and delocalized multicenter-two-electron (nc-2e) bonds in both σ and π frameworks. Electron delocalization is a result of boron's electron deficiency and leads to fluxional behavior, which has been observed in B13(+) and B19(-). A unique capability of the in-plane rotation of the inner atoms against the periphery of the cluster in a chosen direction by employing circularly polarized infrared radiation has been suggested. Such fluxional behaviors in boron clusters are interesting and have been proposed as molecular Wankel motors. The concepts of aromaticity and antiaromaticity have been extended beyond organic chemistry to planar boron clusters. The validity of these concepts in understanding the electronic structures of boron clusters is evident in the striking similarities of the π-systems of planar boron clusters to those of polycyclic aromatic hydrocarbons, such as benzene, naphthalene, coronene, anthracene, or phenanthrene. Chemical bonding models developed for boron clusters not only allowed the rationalization of the stability of boron clusters but also lead to the design of novel metal-centered boron wheels with a record-setting planar coordination number of 10. The unprecedented highly coordinated borometallic molecular wheels provide insights into the interactions between transition metals and boron and expand the frontier of boron chemistry. Another interesting feature discovered through cluster studies is boron transmutation. Even though it is well-known that B(-), formed by adding one electron to boron, is isoelectronic to carbon, cluster studies have considerably expanded the possibilities of new structures and new materials using the B(-)/C analogy. It is

  11. Understanding Boron through Size-Selected Clusters: Structure, Chemical Bonding, and Fluxionality

    Energy Technology Data Exchange (ETDEWEB)

    Sergeeva, Alina P.; Popov, Ivan A.; Piazza, Zachary A.; Li, Wei-Li; Romanescu, Constantin; Wang, Lai S.; Boldyrev, Alexander I.

    2014-04-15

    Conspectus Boron is an interesting element with unusual polymorphism. While three-dimensional (3D) structural motifs are prevalent in bulk boron, atomic boron clusters are found to have planar or quasi-planar structures, stabilized by localized two-center–two-electron (2c–2e) σ bonds on the periphery and delocalized multicenter–two-electron (nc–2e) bonds in both σ and π frameworks. Electron delocalization is a result of boron’s electron deficiency and leads to fluxional behavior, which has been observed in B13+ and B19–. A unique capability of the in-plane rotation of the inner atoms against the periphery of the cluster in a chosen direction by employing circularly polarized infrared radiation has been suggested. Such fluxional behaviors in boron clusters are interesting and have been proposed as molecular Wankel motors. The concepts of aromaticity and antiaromaticity have been extended beyond organic chemistry to planar boron clusters. The validity of these concepts in understanding the electronic structures of boron clusters is evident in the striking similarities of the π-systems of planar boron clusters to those of polycyclic aromatic hydrocarbons, such as benzene, naphthalene, coronene, anthracene, or phenanthrene. Chemical bonding models developed for boron clusters not only allowed the rationalization of the stability of boron clusters but also lead to the design of novel metal-centered boron wheels with a record-setting planar coordination number of 10. The unprecedented highly coordinated borometallic molecular wheels provide insights into the interactions between transition metals and boron and expand the frontier of boron chemistry. Another interesting feature discovered through cluster studies is boron transmutation. Even though it is well-known that B–, formed by adding one electron to boron, is isoelectronic to carbon, cluster studies have considerably expanded the possibilities of new structures and new materials using the B

  12. Characterization and intramolecular bonding patterns of busulfan: Experimental and quantum chemical approach

    Science.gov (United States)

    Karthick, T.; Tandon, Poonam; Singh, Swapnil; Agarwal, Parag; Srivastava, Anubha

    2017-02-01

    The investigations of structural conformers, molecular interactions and vibrational characterization of pharmaceutical drug are helpful to understand their behaviour. In the present work, the 2D potential energy surface (PES) scan has been performed on the dihedral angles C6sbnd O4sbnd S1sbnd C5 and C25sbnd S22sbnd O19sbnd C16 to find the stable conformers of busulfan. In order to show the effects of long range interactions, the structures on the global minima of PES scan have been further optimized by B3LYP/6-311 ++G(d,p) method with and without empirical dispersion functional in Gaussian 09W package. The presence of n → σ* and σ → σ* interactions which lead to stability of the molecule have been predicted by natural bond orbital analysis. The strong and weak hydrogen bonds between the functional groups of busulfan were analyzed using quantum topological atoms in molecules analysis. In order to study the long-range forces, such as van der Waals interactions, steric effect in busulfan, the reduced density gradient as well as isosurface defining these interactions has been plotted using Multiwfn software. The spectroscopic characterization on the solid phase of busulfan has been studied by experimental FT-IR and FT-Raman spectra. From the 13C and 1H NMR spectra, the chemical shifts of individual C and H atoms of busulfan have been predicted. The maximum absorption wavelengths corresponding to the electronic transitions between the highest occupied molecular orbital and the lowest unoccupied molecular orbital of busulfan have been found by UV-vis spectrum.

  13. Organometallic Bonding in an Ullmann-Type On-Surface Chemical Reaction Studied by High-Resolution Atomic Force Microscopy.

    Science.gov (United States)

    Kawai, Shigeki; Sadeghi, Ali; Okamoto, Toshihiro; Mitsui, Chikahiko; Pawlak, Rémy; Meier, Tobias; Takeya, Jun; Goedecker, Stefan; Meyer, Ernst

    2016-10-01

    The on-surface Ullmann-type chemical reaction synthesizes polymers by linking carbons of adjacent molecules on solid surfaces. Although an organometallic compound is recently identified as the reaction intermediate, little is known about the detailed structure of the bonded organometallic species and its influence on the molecule and the reaction. Herein atomic force microscopy at low temperature is used to study the reaction with 3,9-diiododinaphtho[2,3-b:2',3'-d]thiophene (I-DNT-VW), which is polymerized on Ag(111) in vacuum. Thermally sublimated I-DNT-VW picks up a Ag surface atom, forming a CAg bond at one end after removing an iodine. The CAg bond is usually short-lived, and a CAgC organometallic bond immediately forms with an adjacent molecule. The existence of the bonded Ag atoms strongly affects the bending angle and adsorption height of the molecular unit. Density functional theory calculations reveal the bending mechanism, which reveals that charge from the terminus of the molecule is transferred via the Ag atom into the organometallic bond and strengths the local adsorption to the substrate. Such deformations vanish when the Ag atoms are removed by annealing and CC bonds are established.

  14. The adsorption of acrolein on a Pt (1 1 1): A study of chemical bonding and electronic structure

    Science.gov (United States)

    Pirillo, S.; López-Corral, I.; Germán, E.; Juan, A.

    2012-12-01

    The adsorption of acrolein on a Pt (1 1 1) surface was studied using ab-initio and semiempirical calculations. Geometry optimization and densities of states (DOS) curves were carried out using the Vienna Ab-initio Simulation Package (VASP) code. We started our study with the preferential geometries corresponding to the different acrolein/Pt (1 1 1) adsorption modes previously reported. Then, we examined the evolution of the chemical bonding in these geometries, using the crystal orbital overlap population (COOP) and overlap population (OP) analysis of selected pairs of atoms. We analyzed the acrolein intramolecular bonds, Pt (1 1 1) superficial bonds and new moleculesbnd surface formed bonds after adsorption. We found that Ptsbnd Pt bonds interacting with the molecule and acrolein Cdbnd O and Cdbnd C bonds are weakened after adsorption; this last bond is significantly linked to the surface. The obtained Csbnd Pt and Osbnd Pt OP values suggest that the most stable adsorption modes are η3-cis and η4-trans, while the η1-trans is the less favored configuration. We also found that C pz orbital and Pt pz and d orbitals participate strongly in the adsorption process.

  15. Preparation, Physical-Chemical Characterization, and Cytocompatibility of Polymeric Calcium Phosphate Cements

    Science.gov (United States)

    Khashaba, Rania M.; Moussa, Mervet; Koch, Christopher; Jurgensen, Arthur R.; Missimer, David M.; Rutherford, Ronny L.; Chutkan, Norman B.; Borke, James L.

    2011-01-01

    Aim. Physicochemical mechanical and in vitro biological properties of novel formulations of polymeric calcium phosphate cements (CPCs) were investigated. Methods. Monocalcium phosphate, calcium oxide, and synthetic hydroxyapatite were combined with either modified polyacrylic acid, light activated polyalkenoic acid, or polymethyl vinyl ether maleic acid to obtain Types I, II, and III CPCs. Setting time, compressive and diametral strength of CPCs was compared with zinc polycarboxylate cement (control). Specimens were characterized using X-ray diffraction, scanning electron microscopy, and infrared spectroscopy. In vitro cytotoxicity of CPCs and control was assessed. Results. X-ray diffraction analysis showed hydroxyapatite, monetite, and brushite. Acid-base reaction was confirmed by the appearance of stretching peaks in IR spectra of set cements. SEM revealed rod-like crystals and platy crystals. Setting time of cements was 5–12 min. Type III showed significantly higher strength values compared to control. Type III yielded high biocompatibility. Conclusions. Type III CPCs show promise for dental applications. PMID:21941551

  16. Preparation, Physical-Chemical Characterization, and Cytocompatibility of Polymeric Calcium Phosphate Cements

    Directory of Open Access Journals (Sweden)

    Rania M. Khashaba

    2011-01-01

    Full Text Available Aim. Physicochemical mechanical and in vitro biological properties of novel formulations of polymeric calcium phosphate cements (CPCs were investigated. Methods. Monocalcium phosphate, calcium oxide, and synthetic hydroxyapatite were combined with either modified polyacrylic acid, light activated polyalkenoic acid, or polymethyl vinyl ether maleic acid to obtain Types I, II, and III CPCs. Setting time, compressive and diametral strength of CPCs was compared with zinc polycarboxylate cement (control. Specimens were characterized using X-ray diffraction, scanning electron microscopy, and infrared spectroscopy. In vitro cytotoxicity of CPCs and control was assessed. Results. X-ray diffraction analysis showed hydroxyapatite, monetite, and brushite. Acid-base reaction was confirmed by the appearance of stretching peaks in IR spectra of set cements. SEM revealed rod-like crystals and platy crystals. Setting time of cements was 5–12 min. Type III showed significantly higher strength values compared to control. Type III yielded high biocompatibility. Conclusions. Type III CPCs show promise for dental applications.

  17. Production of cellulose phosphate from oil palm empty fruit bunch: Effect of chemical ratio

    Science.gov (United States)

    Rohaizu, R.; Wanrosli, W. D.

    2015-06-01

    Cellulose phosphate was synthesized from oil palm biomass residue that has the potential to represent a considerable added value product for the oil palm biomass utilization. Cellulose phosphate (CP) is prepared viaa phosphorylation process using the H3PO4/P2O5/Et3PO4/hexanol sequence using oil palm empty fruit bunch microcrystalline cellulose (OPEFB-MCC) as the starting material. Various factors affect its synthesis; one of them which is the subject of this investigation is the orthophosphoric acid (H3PO4) to triethylphosphate(Et3PO4) ratio which have the capability to increase the phosphorus content of CP. It is believed that during this reaction, the esterification of the free hydroxyl groups of the cellulose occurred. The H3PO4/Et3PO4 ratios applied were 0.16, 1.00, and 1.84. The effect of the H3PO4/Et3PO4 ratio on phosphorus content, yield, water swelling and molecular structure of CP are discussed.

  18. Nanoscale metals and semiconductors for the storage of solar energy in chemical bonds

    Science.gov (United States)

    Manthiram, Karthish

    The transduction of electrical energy into chemical bonds represents one potential strategy for storing energy derived from intermittent sources such as solar and wind. Driving the electrochemical reduction of carbon dioxide using light requires (1) developing light absorbers which convert photons into electron-hole pairs and (2) catalysts which utilize these electrons and holes to reduce carbon dioxide and oxidize water, respectively. For both the light absorbers and catalysts, the use of nanoscale particles is advantageous, as charge transport length scales are minimized in the case of nanoscale light absorbers and catalytic surface-area-to-volume ratio is maximized for nanoscale catalysts. In many cases, although semiconductors and metals in the form of thin films and foils are increasingly well-characterized as photoabsorbers and electrocatalysts for carbon dioxide reduction, respectively, the properties of their nanoscale counterparts remain poorly understood. This dissertation explores the nature of the light absorption mode of non-stoichiometric semiconductors which are utilized as light absorbers and the development of catalysts with enhanced stability, activity, and selectivity for carbon dioxide reduction. Chapter 1 provides an overview of the state of development of methods of transducing the energy of photons into chemical bonds. Chapters 2 and 3 investigate the development of stable, active, and selective catalysts for the electrochemical reduction of carbon dioxide. Chapter 2 examines how copper nanoparticles have enhanced activities and selectivities for methanation compared to copper foils. Chapter 3 focuses on the development of strategies to stabilize high-surface-area catalysts to prevent surface area loss during electrochemical carbon dioxide reduction. Chapters 4 and 5 entail a fundamental understanding of the light absorption mode of nanoscale photoabsorbers used in both photoelectrochemical cells and in photovoltaics. Chapter 4 focuses on the

  19. Immobilization of fission products in phosphate ceramic waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Singh, D. [Argonne National Lab., IL (United States)

    1996-10-01

    The goal of this project is to develop and demonstrate the feasibility of a novel low-temperature solidification/stabilization (S/S) technology for immobilizing waste streams containing fission products such as cesium, strontium, and technetium in a chemically bonded phosphate ceramic. This technology can immobilize partitioned tank wastes and decontaminate waste streams containing volatile fission products.

  20. Influence of chemical bonding of chlorides with aluminates in cement hidratation process on corrosion steel bars in concrete

    Directory of Open Access Journals (Sweden)

    Bikić Farzet H.

    2010-01-01

    Full Text Available The presence of chlorides in concrete is a permanent subject of research because they cause corrosion of steel bars. Chlorides added to the concrete during preparation, as accelerators of the bonding of cement minerals process, enter into reaction with aluminates, creating a phase known as chloroaluminate hydrates. In everyday conditions the product of chemical bonding between chlorides and aluminates is usually monochloridealuminate C3A·CaCl2·Hx, better known as Friedel's salt. In this paper, the influence of chemical bonding of chlorides with aluminates during the process of cement hydration on corrosion of steel bars in concrete was investigated. The process of chlorides bonding with aluminates yielding monochloride aluminate is monitored by XRD analyses. It was found that the amount of chlorides bonding with aluminates increases with an increase of temperature, and as a result, reduces the amount of 'free' chlorides in concrete. Potentiodynamic measurements have shown that increase in temperature of the heat treatment of working electrodes by chlorides leads to a reduction of steel bars corrosion as a result of either the increase of the monochloride-aluminate content or the decrease of free chlorides amount. Chlorides bound in chloroaluminate hydrates do not cause activation of steel bars corrosion in concrete. It was also proven that the increase of free chlorides concentration in the concrete leads to intensification of steel bars corrosion. This additionally approves that free chlorides are only the activators of process of steel bars corrosion in the concrete.

  1. Chemical Bonding States of TiC Films before and after Hydrogen Ion Irradiation

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    TiC films deposited by rf magnetron sputtering followed by Ar+ ion bombardment were irradiated with a hydrogen ion beam. X-ray photoelectron spectroscopy (XPS) was used for characterization of the chemical bonding states of C and Ti elements of the TiC films before and after hydrogen ion irradiation, in order to understand the effect of hydrogen ion irradiation on the films and to study the mechanism of hydrogen resistance of TiC films. Conclusions can be drawn that ion bombardment at moderate energy can cause preferential physical sputtering of carbon atoms from the surface of low atomic number (Z) material. This means that ion beam bombardment leads to the formation of a non-stoichiometric composition of TiC on the surface.TiC films prepared by ion beam mixing have the more excellent characteristic of hydrogen resistance. One important cause, in addition to TiC itself, is that there are many vacant sites in TiC created by ion beam mixing.These defects can easily trap hydrogen and effectively enhance the effect of hydrogen resistance.

  2. Microstructure and chemical bond evolution of diamond-like carbon films machined by femtosecond laser

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jing; Wang, Chunhui [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Liu, Yongsheng, E-mail: yongshengliu@nwpu.edu.cn [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Cheng, Laifei [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Li, Weinan [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 10068 (China); Zhang, Qing [Science and Technology on Thermostructure Composite Materials Laboratory, Northwestern Polytechnical University, Xi’an 710072 (China); Yang, Xiaojun [State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an 10068 (China)

    2015-06-15

    Highlights: • The machining depth was essentially proportional to the laser power. • The well patterned microgrooves and ripple structures with nanoparticles were formed distinctly in the channels. And the number of nanoparticles increased with the processing power as well. • It revealed a conversion from amorphous carbon to nanocrystalline graphite after laser treated with increasing laser power. • It showed that a great decrease of sp{sup 3}/sp{sup 2} after laser treatment. - Abstract: Femtosecond laser is of great interest for machining high melting point and hardness materials such as diamond-like carbon, SiC ceramic, et al. In present work, the microstructural and chemical bond evolution of diamond-like carbon films were investigated using electron microscopy and spectroscopy techniques after machined by diverse femtosecond laser power in air. The results showed the machining depth was essentially proportional to the laser power. The well patterned microgrooves and ripple structures with nanoparticles were formed distinctly in the channels. Considering the D and G Raman band parameters on the laser irradiation, it revealed a conversion from amorphous carbon to nanocrystalline graphite after laser treated with increasing laser power. X-ray photoelectron spectroscopy analysis showed a great decrease of sp{sup 3}/sp{sup 2} after laser treatment.

  3. Chemical Bonding of Transition-Metal Co13 Clusters with Graphene.

    Science.gov (United States)

    Alonso-Lanza, Tomás; Ayuela, Andrés; Aguilera-Granja, Faustino

    2015-12-01

    We carried out density functional calculations to study the adsorption of Co13 clusters on graphene. Several free isomers were deposited at different positions with respect to the hexagonal lattice nodes, allowing us to study even the hcp 2d isomer, which was recently obtained as the most stable one. Surprisingly, the Co13 clusters attached to graphene prefer icosahedron-like structures in which the low-lying isomer is much distorted; in such structures, they are linked with more bonds than those reported in previous works. For any isomer, the most stable position binds to graphene by the Co atoms that can lose electrons. We find that the charge transfer between graphene and the clusters is small enough to conclude that the Co-graphene binding is not ionic-like but chemical. Besides, the same order of stability among the different isomers on doped graphene is kept. These findings could also be of interest for magnetic clusters on graphenic nanostructures such as ribbons and nanotubes.

  4. Novel Chemically Stable Er3+-Yb3+ Codopded Phosphate Glass for Ion-Exchanged Active Waveguide Devices

    Institute of Scientific and Technical Information of China (English)

    陈宝玉; 赵士龙; 胡丽丽

    2003-01-01

    A novel Er3+-Yb3+ codoped phosphate glass,which combines good chemical durability with good spectroscopic properties,is developed for the ion-exchange process.The relevant properties of this glass are presented for reference in the design and modelling of ion-exchanged active waveguide devices.The weight-loss rate of this glass is 1.45 × 10-5 g.cm-2.h-1 in boiling water,which is comparable to that of Kigre's Q-246 silicate glass.The emission cross section of Er3+ in this glass is calculated to be 0.72 × 10-20 cm2 using the McCumber theory.It is found that a planar waveguide with three modes at 632.8 nm is readily realized in this glass from our primary ion-exchange experiments.

  5. The influenza fusion peptide promotes lipid polar head intrusion through hydrogen bonding with phosphates and N-terminal membrane insertion depth.

    Science.gov (United States)

    Légaré, Sébastien; Lagüe, Patrick

    2014-09-01

    Influenza infection requires fusion between the virus envelope and a host cell endosomal membrane. The influenza hemagglutinin fusion peptide (FP) is essential to viral membrane fusion. It was recently proposed that FPs would fuse membranes by increasing lipid tail protrusion, a membrane fusion transition state. The details of how FPs induce lipid tail protrusion, however, remain to be elucidated. To decipher the molecular mechanism by which FPs promote lipid tail protrusion, we performed molecular dynamics simulations of the wild-type (WT) FP, fusogenic mutant F9A, and nonfusogenic mutant W14A in model bilayers. This article presents the peptide-lipid interaction responsible for lipid tail protrusion and a related lipid perturbation, polar head intrusion, where polar heads are sunk under the membrane surface. The backbone amides from the four N-terminal peptide residues, deeply inserted in the membrane, promoted both perturbations through H bonding with lipid phosphates. Polar head intrusion correlated with peptides N-terminal insertion depth and activity: the N-termini of WT and F9A were inserted deeper into the membrane than nonfusogenic W14A. Based on these results, we propose that FP-induced polar head intrusion would complement lipid tail protrusion in catalyzing membrane fusion by reducing repulsions between juxtaposed membranes headgroups. The presented model provides a framework for further research on membrane fusion and influenza antivirals.

  6. Role of the chemical bonding for the time-dependent electron transport through an interacting quantum dot

    KAUST Repository

    Goker, Ali

    2011-06-01

    A combination of ab initio and many-body calculations is utilized to determine the effects of the bonding in Au electrodes on the time dependent current through a quantum dot suddenly shifted into the Kondo regime by a gate voltage. For an asymmetrically coupled system the instantaneous conductance exhibits fluctuations. The frequencies of the fluctuations turn out to be proportional to the energetic separation between the dominating peaks in the density of states and the Fermi level. The chemical bonding in the electrodes, thus, drastically alters the transient current, which can be accessed by ultrafast pump-probe techniques. © 2011 Elsevier B.V. All rights reserved.

  7. Chemical origin of blue- and redshifted hydrogen bonds: intramolecular hyperconjugation and its coupling with intermolecular hyperconjugation.

    Science.gov (United States)

    Li, An Yong

    2007-04-21

    Upon formation of a H bond Y...H-XZ, intramolecular hyperconjugation n(Z)-->sigma*(X-H) of the proton donor plays a key role in red- and blueshift characters of H bonds and must be introduced in the concepts of hyperconjugation and rehybridization. Intermolecular hyperconjugation transfers electron density from Y to sigma*(X-H) and causes elongation and stretch frequency redshift of the X-H bond; intramolecular hyperconjugation couples with intermolecular hyperconjugation and can adjust electron density in sigma*(X-H); rehybridization causes contraction and stretch frequency blueshift of the X-H bond on complexation. The three factors--intra- and intermolecular hyperconjugations and rehybridization--determine commonly red- or blueshift of the formed H bond. A proton donor that has strong intramolecular hyperconjugation often forms blueshifted H bonds.

  8. A Simple Visualization of Double Bond Properties: Chemical Reactivity and UV Fluorescence

    Science.gov (United States)

    Grayson, Scott M.

    2012-01-01

    A simple, easily visualized thin-layer chromatography (TLC) staining experiment is presented that highlights the difference in reactivity between aromatic double bonds and nonaromatic double bonds. Although the stability of aromatic systems is a major theme in organic chemistry, the concept is rarely reinforced "visually" in the undergraduate…

  9. Chemical bonding and the incorporation of potassium into the Earth's core

    Energy Technology Data Exchange (ETDEWEB)

    Sherman, D.M. (Geological Survey, Denver, CO (USA))

    1990-05-01

    It has been argued that most of the Earth's potassium was segregated into the outer core and that the radioactive decay of {sup 40}K provided the heat source for the geodynamo. This idea rests on the assumption that the affinity of potassium for sulfur or metallic iron is enhanced at high pressure. In this paper, the high pressure electronic structures of K in sulfide, iron sulfide and metallic iron coordination environments were determined from molecular orbital (SCF-X{alpha}-SW) calculations on (KS{sub 8}){sup 15{minus}}, (KS{sub 8}Fe{sub 6}){sup 3{minus}} and KFe{sub 14} clusters. It is shown that, even at high pressure, potassium cannot alloy with metallic iron. Although a high-pressure electronic transition may enhance the potassium-sulfur chemical bond, the electronic structure of the KS{sub 8}Fe{sub 6} cluster shows that this electronic transition cannot happen in an iron sulfide melt. Consequently, potassium will not have an enhanced affinity for sulfur in planetary interiors. If the lower mantle were more reducing, potassium might be excluded from the silicate phases by more strongly lithophile elements and segregated into a metal sulfide phase in the outer core (cf. the phase assemblages in enstatite chondrites). Given the oxidation state of the Earth, however, it is unlikely that significant quantities of potassium have been incorporated into the outer core. The Earth, like the moon and the eucrite parent body, is depleted in potassium. An alternative heat source (e.g., the radioactive decay of U and Th) must be invoked to explain the geodynamo.

  10. Principles and applications of halogen bonding in medicinal chemistry and chemical biology.

    Science.gov (United States)

    Wilcken, Rainer; Zimmermann, Markus O; Lange, Andreas; Joerger, Andreas C; Boeckler, Frank M

    2013-02-28

    Halogen bonding has been known in material science for decades, but until recently, halogen bonds in protein-ligand interactions were largely the result of serendipitous discovery rather than rational design. In this Perspective, we provide insights into the phenomenon of halogen bonding, with special focus on its role in drug discovery. We summarize the theoretical background defining its strength and directionality, provide a systematic analysis of its occurrence and interaction geometries in protein-ligand complexes, and give recent examples where halogen bonding has been successfully harnessed for lead identification and optimization. In light of these data, we discuss the potential and limitations of exploiting halogen bonds for molecular recognition and rational drug design.

  11. Chemically bonded cements formulated with by-products of magnesium oxide

    OpenAIRE

    2008-01-01

    The casting of magnesium and potassium phosphate (KMgPO4•6H2O; K-struvite) cements becomes possible after the aqueous reaction between magnesium oxide and potassium dihydrogen phosphate. This reaction is quite exothermic and allows the resulting paste setting in just few minutes. Those cements, when are cast with magnesium oxides of high purity, are used to retain and encapsulate special residues and as repairing concrete mortar, as it is described in the bibliography. However, it is also pos...

  12. Research on the Interaction of Hydrogen-Bond Acidic Polymer Sensitive Sensor Materials with Chemical Warfare Agents Simulants by Inverse Gas Chromatography

    OpenAIRE

    Liu Yang; Qiang Han; Shuya Cao; Feng Huang; Molin Qin; Chenghai Guo; Mingyu Ding

    2015-01-01

    Hydrogen-bond acidic polymers are important high affinity materials sensitive to organophosphates in the chemical warfare agent sensor detection process. Interactions between the sensor sensitive materials and chemical warfare agent simulants were studied by inverse gas chromatography. Hydrogen bonded acidic polymers, i.e., BSP3, were prepared for micro-packed columns to examine the interaction. DMMP (a nerve gas simulant) and 2-CEES (a blister agent simulant) were used as probes. Chemical an...

  13. The Load and Time Dependence of Chemical Bonding-Induced Frictional Ageing of Silica at the Nanoscale

    Science.gov (United States)

    Tian, K.; Gosvami, N. N.; Goldsby, D. L.; Carpick, R. W.

    2015-12-01

    Rate and state friction (RSF) laws are empirical relationships that describe the frictional behavior of rocks and other materials in experiments, and reproduce a variety of observed natural behavior when employed in earthquake models. A pervasive observation from rock friction experiments is the linear increase of static friction with the log of contact time, or 'ageing'. Ageing is usually attributed to an increase in real area of contact associated with asperity creep. However, recent atomic force microscopy (AFM) experiments demonstrate that ageing of nanoscale silica-silica contacts is due to progressive formation of interfacial chemical bonds in the absence of plastic deformation, in a manner consistent with the multi-contact ageing behavior of rocks [Li et al., 2011]. To further investigate chemical bonding-induced ageing, we explored the influence of normal load (and thus contact normal stress) and contact time on ageing. Experiments that mimic slide-hold-slide rock friction experiments were conducted in the AFM for contact loads and hold times ranging from 23 to 393 nN and 0.1 to 100 s, respectively, all in humid air (~50% RH) at room temperature. Experiments were conducted by sequentially sliding the AFM tip on the sample at a velocity V of 0.5 μm/s, setting V to zero and holding the tip stationary for a given time, and finally resuming sliding at 0.5 μm/s to yield a peak value of friction followed by a drop to the sliding friction value. Chemical bonding-induced ageing, as measured by the peak friction minus the sliding friction, increases approximately linearly with the product of normal load and the log of the hold time. Theoretical studies of the roles of reaction energy barriers in nanoscale ageing indicate that frictional ageing depends on the total number of reaction sites and the hold time [Liu & Szlufarska, 2012]. We combine chemical kinetics analyses with contact mechanics models to explain our results, and develop a new approach for curve

  14. Determining Chemical Reactivity Driving Biological Activity from SMILES Transformations: The Bonding Mechanism of Anti-HIV Pyrimidines

    Directory of Open Access Journals (Sweden)

    Mihai V. Putz

    2013-07-01

    Full Text Available Assessing the molecular mechanism of a chemical-biological interaction and bonding stands as the ultimate goal of any modern quantitative structure-activity relationship (QSAR study. To this end the present work employs the main chemical reactivity structural descriptors (electronegativity, chemical hardness, chemical power, electrophilicity to unfold the variational QSAR though their min-max correspondence principles as applied to the Simplified Molecular Input Line Entry System (SMILES transformation of selected uracil derivatives with anti-HIV potential with the aim of establishing the main stages whereby the given compounds may inhibit HIV infection. The bonding can be completely described by explicitly considering by means of basic indices and chemical reactivity principles two forms of SMILES structures of the pyrimidines, the Longest SMILES Molecular Chain (LoSMoC and the Branching SMILES (BraS, respectively, as the effective forms involved in the anti-HIV activity mechanism and according to the present work, also necessary intermediates in molecular pathways targeting/docking biological sites of interest.

  15. Indications of chemical bond contrast in AFM images of a hydrogen-terminated silicon surface

    Science.gov (United States)

    Labidi, Hatem; Koleini, Mohammad; Huff, Taleana; Salomons, Mark; Cloutier, Martin; Pitters, Jason; Wolkow, Robert A.

    2017-01-01

    The origin of bond-resolved atomic force microscope images remains controversial. Moreover, most work to date has involved planar, conjugated hydrocarbon molecules on a metal substrate thereby limiting knowledge of the generality of findings made about the imaging mechanism. Here we report the study of a very different sample; a hydrogen-terminated silicon surface. A procedure to obtain a passivated hydrogen-functionalized tip is defined and evolution of atomic force microscopy images at different tip elevations are shown. At relatively large tip-sample distances, the topmost atoms appear as distinct protrusions. However, on decreasing the tip-sample distance, features consistent with the silicon covalent bonds of the surface emerge. Using a density functional tight-binding-based method to simulate atomic force microscopy images, we reproduce the experimental results. The role of the tip flexibility and the nature of bonds and false bond-like features are discussed. PMID:28194036

  16. Bader’s Theory of Atoms in Molecules (AIM) and its Applications to Chemical Bonding

    Indian Academy of Sciences (India)

    P SHYAM VINOD KUMAR; V RAGHAVENDRA; V SUBRAMANIAN

    2016-10-01

    In this perspective article, the basic theory and applications of the “Quantum Theory of Atoms in Molecules” have been presented with examples from different categories of weak and hydrogen bonded molecular systems.

  17. Indications of chemical bond contrast in AFM images of a hydrogen-terminated silicon surface

    Science.gov (United States)

    Labidi, Hatem; Koleini, Mohammad; Huff, Taleana; Salomons, Mark; Cloutier, Martin; Pitters, Jason; Wolkow, Robert A.

    2017-02-01

    The origin of bond-resolved atomic force microscope images remains controversial. Moreover, most work to date has involved planar, conjugated hydrocarbon molecules on a metal substrate thereby limiting knowledge of the generality of findings made about the imaging mechanism. Here we report the study of a very different sample; a hydrogen-terminated silicon surface. A procedure to obtain a passivated hydrogen-functionalized tip is defined and evolution of atomic force microscopy images at different tip elevations are shown. At relatively large tip-sample distances, the topmost atoms appear as distinct protrusions. However, on decreasing the tip-sample distance, features consistent with the silicon covalent bonds of the surface emerge. Using a density functional tight-binding-based method to simulate atomic force microscopy images, we reproduce the experimental results. The role of the tip flexibility and the nature of bonds and false bond-like features are discussed.

  18. Chemical Reactions of Metal-Metal Bonded Compounds of the Transition Elements.

    Science.gov (United States)

    1981-05-18

    methanol, has led to the isolation ot solvento complexes , e.g. Mo2 Cl4 (PPh3 )2 (MeOH)2, in which onc ot the ligands L in XLI is replaced by a solvent...Hexa- and Other Polynuclear Complexes .... 8 2. Formation of Metal-Metal Bonds.................... .................... 11 2.1. From Mononuclear...17 2.3. By Addition of a Metal Complex or Fragment Across an M-X Multiple Bond

  19. Chemical-assisted bonding of thermoplastics/elastomer for fabricating microfluidic valves.

    Science.gov (United States)

    Gu, Pan; Liu, Ke; Chen, Hong; Nishida, Toshikazu; Fan, Z Hugh

    2011-01-01

    Thermoplastics such as cyclic olefin copolymer (COC) and polymethylmethacrylate (PMMA) have been increasingly used in fabricating microfluidic devices. However, the state-of-the-art microvalve technology is a polydimethylsiloxane (PDMS)-based three-layer structure. In order to integrate such a valve with a thermoplastics-based microfluidic device, a bonding method for thermoplastics/PDMS must be developed. We report here a method to bond COC with PDMS through surface activation by corona discharge, surface modification using 3-(trimethoxysilyl)propyl methacrylate (TMSPMA), and thermal annealing. The method is also applicable to PMMA. The bonding strength between thermoplastics and PDMS was represented by the peeling force, which was measured using a method established by the International Organization for Standardization (ISO). The bonding strength measurement offered an objective and quantitative indicator for protocol optimization, as well as comparison with other PDMS-associated bonding methods. Using optimized bonding conditions, two valve arrays were fabricated in a COC/PDMS/COC device and cyclic operations of valve closing/opening were successfully demonstrated. The valve-containing devices withstood 100 psi (∼689 KPa) without delamination. Further, we integrated such valve arrays in a device for protein separation and demonstrated isoelectric focusing in the presence of valves.

  20. Chemical bonding and magnetic properties of gadolinium (Gd) substituted cobalt ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Puli, Venkata Sreenivas, E-mail: vspuli@utep.edu [Department of Mechanical Engineering, University of Texas, El Paso, TX 79968 (United States); Adireddy, Shiva [Department of Physics and Engineering Physics, Tulane University, New Orleans, LA 70118 (United States); Ramana, C.V. [Department of Mechanical Engineering, University of Texas, El Paso, TX 79968 (United States)

    2015-09-25

    Graphical abstract: Room temperature Raman spectra of CoFe{sub 2−x}Gd{sub x}O{sub 4} (CFGO, x = 0.0–0.3) compounds as a function of wavenumber (cm{sup −1}). - Highlights: • Gd substituted ferrites were synthesized under controlled concentration. • Gd ion induced lattice dynamical changes are significant. • Enhanced magnetization is observed upon Gd-incorporation in cobalt ferrite. • A correlation between lattice dynamics and magnetic properties is established. - Abstract: Polycrystalline gadolinium (Gd) substituted cobalt ferrites (CoFe{sub 2−x}Gd{sub x}O{sub 4}; x = 0–0.3, referred to CFGO) ceramics have been synthesized by solid state reaction method. Chemical bonding, crystal structure and magnetic properties of CFGO compounds have been evaluated as a function of Gd-content. X-ray diffraction (XRD) and Raman spectroscopic analyses confirmed the formation of inverse spinel cubic structure. However, a secondary ortho-ferrite phase (GdFeO{sub 3}) nucleates for higher values of Gd-content. A considerable increase in the saturation magnetization has been observed upon the initial substitution of Gd (x = 0.1). The saturation magnetization drastically decreases at higher Gd content (x ⩾ 0.3). No contribution from ortho-ferrite GdFeO{sub 3} phase is noted to the magnetic properties. The increase in the magnetic saturation magnetization is attributed to the higher magnetic moment of Gd{sup 3+} (4f{sup 7}) residing in octahedral sites is higher when compared to that of Fe{sup 3+} (3d{sup 5}) and as well due to the migration of Co{sup 2+} (3d{sup 7}) ions from the octahedral to the tetrahedral sites with a magnetic moment aligned anti-parallel to those of rare earth (RE{sup 3+}) ions in the spinel lattice. Increase in coercivity with increase in Gd{sup 3+} is content is attributed to magnetic anisotropy in the ceramics.

  1. What a difference a bond makes: the structural, chemical, and physical properties of methyl-terminated Si(111) surfaces.

    Science.gov (United States)

    Wong, Keith T; Lewis, Nathan S

    2014-10-21

    The chemical, electronic, and structural properties of surfaces are affected by the chemical termination of the surface. Two-step halogenation/alkylation of silicon provides a scalable, wet-chemical method for grafting molecules onto the silicon surface. Unlike other commonly studied wet-chemical methods of surface modification, such as self-assembly of monolayers on metals or hydrosilylation on silicon, the two-step method enables attachment of small alkyl chains, even methyl groups, to a silicon surface with high surface coverage and homogeneity. The methyl-terminated Si(111) surface, by comparison to hydrogen-terminated Si(111), offers a unique opportunity to study the effects of the first surface bond connecting the overlayer to the surface. This Account describes studies of methyl-terminated Si(111), which have shown that the H-Si(111) and CH3-Si(111) surfaces are structurally nearly identical, yet impart significantly different chemical and electronic properties to the resulting Si surface. The structure of methyl-terminated Si(111) formed by a two-step halogenation/methylation process has been studied by a variety of spectroscopic methods. A covalent Si-C bond is oriented normal to the surface, with the methyl group situated directly atop a surface Si atom. Multiple spectroscopic methods have shown that methyl groups achieve essentially complete coverage of the surface atoms while maintaining the atomically flat, terraced structure of the original H-Si(111) surface. Thus, the H-Si(111) and CH3-Si(111) surface share essentially identical structures aside from the replacement of a Si-H bond with a Si-C bond. Despite their structural similarity, hydrogen and methyl termination exhibit markedly different chemical passivation. Specifically, CH3-Si(111) exhibits significantly greater oxidation resistance than H-Si(111) in air and in aqueous electrolyte under photoanodic current flow. Both surfaces exhibit similar thermal stability in vacuum, and the Si-H and Si

  2. CHEMICALLY BONDED CEMENTS FROM BOILER ASH AND SLUDGE WASTES. PHASE I REPORT AUGUST 1997 - JULY 1998

    Energy Technology Data Exchange (ETDEWEB)

    SUGAMA,T.; YAGER,K.A.

    2002-08-05

    In exploring methods to recycle boiler ash (BA) and waste water treatment sludge (WWTS), by-products generated from Keyspan's power plants, into commercially viable materials, we synthesized chemically bonded cements (CBC) offering the following three specific characteristics; (1) immobilization of hazardous heavy metals, such as Pb, Ni, and V, (2) rapid hardening and setting properties, and (3) development of high mechanical strength. The CBCs were prepared through an acid-base reaction between these by-products acting as the solid base reactants and the sodium polyphosphate solution as the cement-forming acid reactant, followed by a hydrating reaction. Furthermore, two additives, the calcium aluminate cements (CAC) and the calcium silicate cements (CSC) were incorporated into the CBC systems to improve their properties. Using a CBC formulation consisting of 53.8 wt% WWTS, 23.1 wt% CSC, and 23.1 wt% [40 wt% -(-NaPO{sub 3}-)-{sub n}]{sub 2} the Toxicity Characteristics Leaching Procedure (TCLP) tests showed that the concentrations of Pb, Ni, and V metals leached out from the specimens were minimal. This formulation originally contained {approx} 28800 mg/kg of Pb, {approx} 6300 mg/kg of Ni, and {approx} 11130 mg/kg of V; the amounts leaching into the acid extraction fluid were only 0.15 mg/L of Pb, 0.15 mg/L of Ni, and 4.63 mgiL of V. On the other hand, CBC specimens derived from a formulation consisting of 42 wt% BA, 18 wt% CAC and 40 wt% [40 wt% -(-NaPO{sub 3}-)-{sub n}] displayed an excellent compressive strength of 10.8 MPa at an early curing age of 2 hours after mixing at room temperature. The reason for its rapid hardening was due to a high exothermic energy evolved by the acid-base reaction. Furthermore, when these specimens were immersed for 28 days in water at 25 C, and exposed for 20 hours to steam at 80 C, a very high compressive strength of 3.32 MPa developed. Two physico-chemical factors played an important role in improving the mechanical strength

  3. Chemical degradation of trimethyl phosphate as surrogate for organo-phosporus pesticides on nanostructured metal oxides

    Energy Technology Data Exchange (ETDEWEB)

    Štengl, Václav, E-mail: stengl@iic.cas.cz; Henych, Jiří; Grygar, Tomáš; Pérez, Raúl

    2015-01-15

    Nanostructured TiO{sub 2} and mixed oxides of Ti and Fe, Hf, In, Mn or Zr -were prepared by homogeneous hydrolysis of aqueous solution of metal sulphates with urea. The oxides were characterised by X-ray powder diffraction (XRD), scanning electron microscopy, particle size distribution, surface area and porosity. The oxide materials consists of a few nanometre primary crystals (mainly anatase) arranged in a few micrometre regular spherical agglomerates with specific surface area 133–511 m{sup 2} g{sup −1}. The FTIR diffuse spectroscopy was used for monitoring chemical degradation of trimethylphosphate (TMP) as a surrogate for organo-phosphorus pesticides under ambient and higher temperatures. Undoped TiO{sub 2} and Ti,Mn-mixed oxide were most active in cleavage (hydrolysis) of CH{sub 3}O from TMP at room temperature and 100 °C. Cleavage of CH{sub 3}O in the other studied mixed oxides was not complete until temperature exceeds the boiling point of TMP.

  4. Comparison of shear bond strength of resin reinforced chemical cure glass ionomer, conventional chemical cure glass ionomer and chemical cure composite resin in direct bonding systems: an in vitro study.

    Science.gov (United States)

    Rao, Kolasani Srinivasa; Reddy, T Praveen Kumar; Yugandhar, Garlapati; Kumar, B Sunil; Reddy, S N Chandrasekhar; Babu, Devatha Ashok

    2013-01-01

    The acid pretreatment and use of composite resins as the bonding medium has disadvantages like scratching and loss of surface enamel, decalcification, etc. To overcome disadvantages of composite resins, glass ionomers and its modifications are being used for bonding. The study was conducted to evaluate the efficiency of resin reinforced glass ionomer as a direct bonding system with conventional glass ionomer cement and composite resin. The study showed that shear bond strength of composite resin has the higher value than both resin reinforced glass ionomer and conventional glass ionomer cement in both 1 and 24 hours duration and it increased from 1 to 24 hours in all groups. The shear bond strength of resin reinforced glass ionomer cement was higher than the conventional glass ionomer cement in both 1 and 24 hours duration. Conditioning with polyacrylic acid improved the bond strength of resin reinforced glass ionomer cement significantly but not statistically significant in the case of conventional glass ionomer cement.

  5. Influence of moderate pre-oxidation treatment on the physical, chemical and phosphate adsorption properties of iron-containing activated carbon.

    Science.gov (United States)

    Wang, Zhengfang; Shi, Mo; Li, Jihua; Zheng, Zheng

    2014-03-01

    A novel adsorbent based on iron oxide dispersed over activated carbon (AC) were prepared, and used for phosphate removal from aqueous solutions. The influence of pre-oxidation treatment on the physical, chemical and phosphate adsorption properties of iron-containing AC were determined. Two series of ACs, non-oxidized and oxidized carbon modified by iron (denoted as AC-Fe and AC/O-Fe), resulted in a maximum impregnated iron of 4.03% and 7.56%, respectively. AC/O-Fe showed 34.0%-46.6% higher phosphate removal efficiency than the AC-Fe did. This was first attributed to the moderate pre-oxidation of raw AC by nitric acid, achieved by dosing Fe(II) after a pre-oxidation, to obtain higher iron loading, which is favorable for phosphate adsorption. Additionally, the in-situ formed active site on the surface of carbon, which was derived from the oxidation of Fe(II) by nitric acid dominated the remarkably high efficiency with respect to the removal of phosphate. The activation energy for adsorption was calculated to be 10.53 and 18.88 kJ/mol for AC-Fe and AC/O-Fe, respectively. The results showed that the surface mass transfer and intra-particle diffusion were simultaneously occurring during the process and contribute to the adsorption mechanism.

  6. A periodic energy decomposition analysis method for the investigation of chemical bonding in extended systems

    Energy Technology Data Exchange (ETDEWEB)

    Raupach, Marc; Tonner, Ralf, E-mail: tonner@chemie.uni-marburg.de [Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Straße, 35032 Marburg (Germany)

    2015-05-21

    The development and first applications of a new periodic energy decomposition analysis (pEDA) scheme for extended systems based on the Kohn-Sham approach to density functional theory are described. The pEDA decomposes the bonding energy between two fragments (e.g., the adsorption energy of a molecule on a surface) into several well-defined terms: preparation, electrostatic, Pauli repulsion, and orbital relaxation energies. This is complemented by consideration of dispersion interactions via a pairwise scheme. One major extension toward a previous implementation [Philipsen and Baerends, J. Phys. Chem. B 110, 12470 (2006)] lies in the separate discussion of electrostatic and Pauli and the addition of a dispersion term. The pEDA presented here for an implementation based on atomic orbitals can handle restricted and unrestricted fragments for 0D to 3D systems considering periodic boundary conditions with and without the determination of fragment occupations. For the latter case, reciprocal space sampling is enabled. The new method gives comparable results to established schemes for molecular systems and shows good convergence with respect to the basis set (TZ2P), the integration accuracy, and k-space sampling. Four typical bonding scenarios for surface-adsorbate complexes were chosen to highlight the performance of the method representing insulating (CO on MgO(001)), metallic (H{sub 2} on M(001), M = Pd, Cu), and semiconducting (CO and C{sub 2}H{sub 2} on Si(001)) substrates. These examples cover diverse substrates as well as bonding scenarios ranging from weakly interacting to covalent (shared electron and donor acceptor) bonding. The results presented lend confidence that the pEDA will be a powerful tool for the analysis of surface-adsorbate bonding in the future, enabling the transfer of concepts like ionic and covalent bonding, donor-acceptor interaction, steric repulsion, and others to extended systems.

  7. Reactive calcium-phosphate-containing poly(ester-co-ether) methacrylate bone adhesives: chemical, mechanical and biological considerations.

    Science.gov (United States)

    Zhao, Xin; Olsen, Irwin; Li, Haoying; Gellynck, Kris; Buxton, Paul G; Knowles, Jonathan C; Salih, Vehid; Young, Anne M

    2010-03-01

    A poly(propylene glycol-co-lactide) dimethacrylate adhesive with monocalcium phosphate monohydrate (MCPM)/beta-tricalcium phosphate (beta-TCP) fillers in various levels has been investigated. Water sorption by the photo-polymerized materials catalyzed varying filler conversion to dicalcium phosphate (DCP). Polymer modulus was found to be enhanced upon raising total calcium phosphate content. With greater DCP levels, faster release of phosphate and calcium ions and improved buffering of polymer degradation products were observed. This could reduce the likelihood of pH-catalyzed bulk degradation and localized acid production and thereby may prevent adverse biological responses. Bone-like MG-63 cells were found to attach, spread and have normal morphology on both the polymer and composite surfaces. Moreover, composites implanted into chick embryo femurs became closely apposed to the host tissue and did not appear to induce adverse immunological reaction. The above results suggest that the new composite materials hold promise as clinical effective bone adhesives.

  8. CHEMICALLY BONDED CEMENTS FROM BOILER ASH AND SLUDGE WASTES. PHASE II REPORT, SEPT.1998-JULY 1999.

    Energy Technology Data Exchange (ETDEWEB)

    SUGAMA,T.YAGER,K.A.BLANKENHORN,D.(KEYSPAN R AND D INITIATIVE)

    1999-08-01

    Based upon the previous Phase I research program aimed at looking for ways of recycling the KeySpan-generated wastes, such as waste water treatment sludge (WWTS) and bottom ash (BA), into the potentially useful cementitious materials called chemically bonded cement (CBC) materials, the emphasis of this Phase II program done at Brookhaven National Laboratory, in a period of September 1998 through July 1999, was directed towards the two major subjects: One was to assess the technical feasibility of WWTS-based CBC material for use as Pb-exchange adsorbent (PEA) which remediates Pb-contaminated soils in the field; and the other was related to the establishment of the optimum-packaging storage system of dry BA-based CBC components that make it a promising matrix material for the steam-cured concrete products containing sand and coarse aggregate. To achieve the goal of the first subject, a small-scale field demonstration test was carried out. Using the PEA material consisting of 30 wt% WWTS, 13 wt% Type I cement and 57 wt% water, the PES slurry was prepared using a rotary shear concrete mixer, and then poured on the Pb-contaminated soil. The PEA-to-soil ratio by weight was a factor of 2.0. The placed PEA slurry was blended with soil using hand mixing tools such as claws and shovels. The wettability of soils with the PEA was very good, thereby facilitating the soil-PEA mix procedures. A very promising result was obtained from this field test; in fact, the mount of Pb leached out from the 25-day-aged PEA-treated soil specimen was only 0.74 mg/l, meeting the requirement for EPA safe regulation of < 5 mg/l. In contrast, a large amount (26.4 mg/l) of Pb was detected from the untreated soil of the same age. Thus, this finding demonstrated that the WWTS-based CBC has a potential for use as PEA material. Regarding the second subject, the dry-packed storage system consisting of 68.7 wt% BA, 13.0 wt% calcium aluminate cement (CAC), 13.0 wt% Type I portland cement and 5.3 wt

  9. The electron density distribution in the hydrogen bond. A quantum chemical and crystallographic study

    NARCIS (Netherlands)

    Feil, Dirk

    1990-01-01

    With the help of Hartree—Fock—Slater calculations in which very large basis sets are employed, the polarisation of the water molecule by an electric field is explored. The various features in the electron density distribution are encountered again in the long hydrogen bond in the water dimer, showin

  10. Physico-Chemical Factors Affecting Hydrothermal Resistance and Bonding of Polymeric Composites to Steel Surfaces

    Science.gov (United States)

    1985-11-01

    7 , I 71iil 7 7 771111011111111111171111 Type A consists of a strong ionic interaction associated with charge transfer bonding mechanisms which...the ionic interaction regions and the density of entangleicnt macromol- ecules at interfaces are not evident from the limited data. Nevertheless

  11. Progress of removing magnesium impurity from phosphate rock with chemical method%化学法脱除磷矿中镁杂质的研究进展

    Institute of Scientific and Technical Information of China (English)

    刘荣; 郑之银; 陈宇; 许昕; 沈浩

    2012-01-01

    Because flotation is only applicable to individual types of phosphate rock for impurity removal, it can not meet the actual requirements of medium and low grade phosphate rock. The influence of the existence of magnesium impurities in the phosphate rock on phosphoric acid and its downstream products is analyzed. The principle, process and effect of magnesium impurity removal from phosphate rock with chemical methods are introduced. The application about various chemical drugs to the magnesium impurity removal by chemical leaching field and their effects are summarized including organic acid, inorganic acid and acidic gas. The view is proposed that chemical method has the good effect because of its strong selectivity.%浮选法只适用于个别种类的磷矿除杂,不能满足中低品住磷矿脱镁的要求。分析磷矿中镁杂质对磷酸及其下游磷化工产品生产的影响;阐述化学法脱除磷矿中镁杂质的原理、工艺方法及脱镁效果。特别对有机酸、无机酸、酸性气体等化学浸提剂在化学浸提法脱镁研究中的应用和脱镁效果进行了总结,认为化学法脱镁,由于其选择性强,脱镁效果相对较好。

  12. Effect of Catchment Area Activities on the Physico – Chemical Characteristics of Water of Upper Lake, Bhopal with Special Reference to Nitrate and Phosphate Concentration

    Directory of Open Access Journals (Sweden)

    Ranjana Talwar

    2014-04-01

    Full Text Available With the tremendous influx of people and consequent urban development, increased anthropogenic activities in the catchment, inflow of untreated sewage, nutrients and pesticides from urban and rural areas, the water quality of Upper Lake, Bhopal has deteriorated significantly. An attempt has been made to study various physico – chemical parameters, specifically nitrates and phosphates of five different sampling sites of Upper Lake and to study the effect of catchment area activities on these sites.

  13. Extraordinarily Long 2-Electron - 4-Center (2e-/4c) 2.9-Å Carbon-Carbon Bonds - What is a Chemical Bond?

    OpenAIRE

    Miller, Joel S.

    2014-01-01

    Carbon-carbon (CC) bonding is a key essence of organic and biochemistry. The length of a CC bond, i.e. 1.54 Å found in the diamond allotrope of carbon and ethane, is among the essential information learned by all chemistry students. This is the length of a single bond () between sp3-hybridized carbons and is the longest of all common CC bonds. Our studies of the [TCNE]22- (TCNE = tetracyanoethylene) dimers reveal that 2.89 ± 0.05 Å 2 electron/4 center (2e-/4c) CC bonds are present. Struc...

  14. Chemical synthesis of La1 isolated from the venom of the scorpion Liocheles australasiae and determination of its disulfide bonding pattern.

    Science.gov (United States)

    Nagao, Junya; Miyashita, Masahiro; Nakagawa, Yoshiaki; Miyagawa, Hisashi

    2015-08-01

    La1 is a 73-residue cysteine-rich peptide isolated from the scorpion Liocheles australasiae venom. Although La1 is the most abundant peptide in the venom, its biological function remains unknown. Here, we describe a method for efficient chemical synthesis of La1 using the native chemical ligation (NCL) strategy, in which three peptide components of less than 40 residues were sequentially ligated. The peptide thioester necessary for NCL was synthesized using an aromatic N-acylurea approach with Fmoc-SPPS. After completion of sequential NCL, disulfide bond formation was carried out using a dialysis method, in which the linear peptide dissolved in an acidic solution was dialyzed against a slightly alkaline buffer to obtain correctly folded La1. Next, we determined the disulfide bonding pattern of La1. Enzymatic and chemical digests of La1 without reduction of disulfide bonds were analyzed by liquid chromatography/mass spectrometry (LC/MS), which revealed two of four disulfide bond linkages. The remaining two linkages were assigned based on MS/MS analysis of a peptide fragment containing two disulfide bonds. Consequently, the disulfide bonding pattern of La1 was found to be similar to that of a von Willebrand factor type C (VWC) domain. To our knowledge, this is the first report of the experimental determination of the disulfide bonding pattern of peptides having a single VWC domain as well as their chemical synthesis. La1 synthesized in this study will be useful for investigation of its biological role in the venom.

  15. First-Principles Calculations on Electronic, Chemical Bonding and Optical Properties of Cubic Hf3N4

    Institute of Scientific and Technical Information of China (English)

    FENG Li-Ping; WANG Zhi-Qiang; LIU Zheng-Tang

    2013-01-01

    Electronic,chemical bonding and optical properties of cubic Hf3N4(c-Hf3N4) are calculated using the firstprinciples based on the density functional theory (DFT).The optimized lattice parameter is in good agreement with the available experimental and calculational values.Band structure shows that c-Hf3N4 has direct band gap.Densities of states (DOS) and charge densities indicate that the bonding between Hf and N is ionic.The optical properties including complex dielectric function,refractive index,extinction coefficient,absorption coefficient,and reflectivity are predicted.From the theory of crystal-field and molecudar-orbital bonding,the optical transitions of c-Hf3N4 affected by the electronic structure and molecular orbital are studied.It is found that the absorptive transitions of c-Hf3N4 compound are predominantly composed of the transitions from N T22p valence bands to HfT2 (dxy,dxz,dyz) conduction bands.

  16. Evaluation of molecular assembly, spectroscopic interpretation, intra-/inter molecular hydrogen bonding and chemical reactivity of two pyrrole precursors

    Science.gov (United States)

    Rawat, Poonam; Singh, R. N.

    2014-10-01

    This paper describes the evaluation of conformational, spectroscopic, hydrogen bonding and chemical reactivity of pyrrole precursor: ethyl 3,5 dimethyl-1H-pyrrole-2-carboxylate (EDPC) and ethyl 3,4-dimethyl-4-acetyl-1H-pyrrole-2-carboxylate (EDAPC) for the convenient characterization, synthetic usefulness and comparative evaluations. All experimental spectral values of 1H NMR, UV-Vis and FT-IR spectra coincide well with calculated values by DFT. The orbital interactions in EDPC and EDAPC are found to lengthen their Nsbnd H and Cdbnd O bonds and lowers their vibrational frequencies (red shift) resulting to dimer formation. The QTAIM and NBO analyses provide the strength of interactions and charge transfer in the hydrogen bonding unit and stability of dimers. The binding energy of EDPC and EDPAC dimer are found to be 9.92, 10.22 kcal/mol, respectively. In EDPAC and EDPC dimer, hyperconjugative interactions between monomer units is due to n1(O) → σ*(Nsbnd H) that stabilize the molecule up to 9.7 and 9.3 kcal/mol, respectively. On evaluation of molecular electrostatic potential (MEP) and electronic descriptors for EDPC it has been found that it is a good precursor for synthesis of formyl and acetyl derivatives whereas EDAPC has been found to be a good precursor for synthesis of schiff base, hydrazones, hydrazide-hydrazones and chalcones.

  17. Significantly Dense Two-Dimensional Hydrogen-Bond Network in a Layered Zirconium Phosphate Leading to High Proton Conductivities in Both Water-Assisted Low-Temperature and Anhydrous Intermediate-Temperature Regions.

    Science.gov (United States)

    Gui, Daxiang; Zheng, Tao; Xie, Jian; Cai, Yawen; Wang, Yaxing; Chen, Lanhua; Diwu, Juan; Chai, Zhifang; Wang, Shuao

    2016-12-19

    A highly stable layered zirconium phosphate, (NH4)2[ZrF2(HPO4)2] (ZrP-1), was synthesized by an ionothermal method and contains an extremely dense two-dimensional hydrogen-bond network that is thermally stable up to 573 K, leading to combined ultrahigh water-assisted proton conductivities of 1.45 × 10(-2) S cm(-1) at 363 K/95% relative humidity and sustainable anhydrous proton conductivity of 1.1 × 10(-5) S cm(-1) at 503 K.

  18. Adsorption of 2-mercaptobenzothiazole on copper surface from phosphate solutions

    Science.gov (United States)

    Kazansky, L. P.; Selyaninov, I. A.; Kuznetsov, Yu. I.

    2012-07-01

    Analysis of the electrochemical and XPS results has shown that adsorption of 2-mercaptobenzothiazole (MBT) on copper electrodes in neutral phosphate solutions proceeds through the formation of the chemical bonds by copper (I) cations with exo-sulfur and nitrogen atoms. A protection layer formed of Cu(I)MBT complex prevents precipitation of copper (II) phosphate on a copper surface. The thickness of the surface film consisting of a complex [Cu(I)MBT]n (having probably polymeric nature), where MBT acts as at least three-dentate ligand, increases depending on the exposure time, reaching 8-9 nm after immersing for 12 h in test solution. Even in a case of the preliminary formation of copper (II) phosphate on the copper electrode at the anodic potential addition of small amounts of MBT results in complete removal of copper (II) phosphate from the surface.

  19. Analytic projection from plane-wave and PAW wavefunctions and application to chemical-bonding analysis in solids.

    Science.gov (United States)

    Maintz, Stefan; Deringer, Volker L; Tchougréeff, Andrei L; Dronskowski, Richard

    2013-11-05

    Quantum-chemical computations of solids benefit enormously from numerically efficient plane-wave (PW) basis sets, and together with the projector augmented-wave (PAW) method, the latter have risen to one of the predominant standards in computational solid-state sciences. Despite their advantages, plane waves lack local information, which makes the interpretation of local densities-of-states (DOS) difficult and precludes the direct use of atom-resolved chemical bonding indicators such as the crystal orbital overlap population (COOP) and the crystal orbital Hamilton population (COHP) techniques. Recently, a number of methods have been proposed to overcome this fundamental issue, built around the concept of basis-set projection onto a local auxiliary basis. In this work, we propose a novel computational technique toward this goal by transferring the PW/PAW wavefunctions to a properly chosen local basis using analytically derived expressions. In particular, we describe a general approach to project both PW and PAW eigenstates onto given custom orbitals, which we then exemplify at the hand of contracted multiple-ζ Slater-type orbitals. The validity of the method presented here is illustrated by applications to chemical textbook examples-diamond, gallium arsenide, the transition-metal titanium-as well as nanoscale allotropes of carbon: a nanotube and the C60 fullerene. Remarkably, the analytical approach not only recovers the total and projected electronic DOS with a high degree of confidence, but it also yields a realistic chemical-bonding picture in the framework of the projected COHP method.

  20. Influence of bath PH value on microstructure and corrosion resistance of phosphate chemical conversion coating on sintered Nd-Fe-B permanent magnets

    Science.gov (United States)

    Ding, Xia; Xue, Long-fei; Wang, Xiu-chun; Ding, Kai-hong; Cui, Sheng-li; Sun, Yong-cong; Li, Mu-sen

    2016-10-01

    The effect of bath PH value on formation, microstructure and corrosion resistance of the phosphate chemical conversion (PCC) coatings as well as the effect on the magnetic property of the magnets is investigated in this paper. The results show that the coating mass and thickness increase with the decrease of the bath PH value. Scanning electron microscopy observation demonstrates that the PCC coatings are in a blocky structure with different grain size. Transmission electron microscope and X-ray diffractometer tests reveal the coatings are polycomponent and are mainly composed of neodymium phosphate hydrate and praseodymium phosphate hydrate. The electrochemical analysis and static immersion corrosion test show the corrosion resistance of the PCC coatings prepared at bath PH value of 0.52 is worst. Afterwards the corrosion resistance increases first and then decreases with the increasing of the bath PH values. The magnetic properties of all the samples with PCC treatment are decreased. The biggest loss is occurred when the bath PH value is 0.52. Taken together, the optimum PH range of 1.00-1.50 for the phosphate solution has been determined.

  1. Effect of applied dc bias voltage on composition, chemical bonding and mechanical properties of carbon nitride films prepared by PECVD

    Institute of Scientific and Technical Information of China (English)

    LI Hong-xuan; XU Tao; HAO Jun-ying; CHEN Jian-min; ZHOU Hui-di; XUE Qun-ji; LIU Hui-wen

    2004-01-01

    Carbon nitride films were deposited on Si (100) substrates using plasma-enhanced chemical vapor deposition (PECVD) technique from CH4 and N2 at different applied dc bias voltage. The microstructure, composition and chemical bonding of the resulting films were characterized by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The mechanical properties such as hardness and elastic modulus of the films were evaluated using nano-indentation. As the results, the Raman spectra, showing the G and D bands, indicate the amorphous structure of the films. XPS and FTIR measurements demonstrate the existence of various carbon-nitride bonds in the films and the hydrogenation of carbon nitride phase. The composition ratio of N to C, the nano-hardness and the elastic modulus of the carbon nitride films increase with increasing dc bias voltage and reach the maximums at a dc bias voltage of 300 V, then they decrease with further increase of the dc bias voltage. Moreover, the XRD analyses indicate that the carbon nitride film contains some polycrystalline C3N4 phase embedded in the amorphous matrix at optimized deposition condition of dc bias voltage of 300 V.

  2. Structure-property relationships in cubic cuprous iodide: A novel view on stability, chemical bonding, and electronic properties.

    Science.gov (United States)

    Pishtshev, A; Karazhanov, S Zh

    2017-02-14

    Based on the combination of density functional theory and theory-group methods, we performed systematic modeling of γ-CuI structural design at the atomistic level. Being started from the metallic copper lattice, we treated a crystal assembly as a stepwise iodination process characterized in terms of a sequence of intermediate lattice geometries. These geometries were selected and validated via screening of possible structural transformations. The genesis of chemical bonding was studied for three structural transformations by analyzing the relevant changes in the topology of valence electron densities. We determined structural trends driven by metal-ligand coupling. This allowed us to suggest the improved scenario of chemical bonding in γ-CuI. In particular, the unconventional effect of spatial separation of metallic and covalent interactions was found to be very important with respect to the preferred arrangements of valence electrons in the iodination process. We rigorously showed that useful electronic and optical properties of γ-CuI originate from the combination of two separated bonding patterns-strong covalency established in I-Cu tetrahedral connections and noncovalent interactions of copper cores is caused by the 3d(10) closed-shell electron configurations. The other finding of ours is that the self-consistency of the GW calculations is crucial for correctly determining the dynamic electronic correlations in γ-CuI. Detail reinvestigation of the quasi-particle energy structure by means of the self-consistent GW approach allowed us to explain how p-type electrical conductivity can be engineered in the material.

  3. Structure-property relationships in cubic cuprous iodide: A novel view on stability, chemical bonding, and electronic properties

    Science.gov (United States)

    Pishtshev, A.; Karazhanov, S. Zh.

    2017-02-01

    Based on the combination of density functional theory and theory-group methods, we performed systematic modeling of γ-CuI structural design at the atomistic level. Being started from the metallic copper lattice, we treated a crystal assembly as a stepwise iodination process characterized in terms of a sequence of intermediate lattice geometries. These geometries were selected and validated via screening of possible structural transformations. The genesis of chemical bonding was studied for three structural transformations by analyzing the relevant changes in the topology of valence electron densities. We determined structural trends driven by metal-ligand coupling. This allowed us to suggest the improved scenario of chemical bonding in γ-CuI. In particular, the unconventional effect of spatial separation of metallic and covalent interactions was found to be very important with respect to the preferred arrangements of valence electrons in the iodination process. We rigorously showed that useful electronic and optical properties of γ-CuI originate from the combination of two separated bonding patterns—strong covalency established in I-Cu tetrahedral connections and noncovalent interactions of copper cores is caused by the 3d10 closed-shell electron configurations. The other finding of ours is that the self-consistency of the GW calculations is crucial for correctly determining the dynamic electronic correlations in γ-CuI. Detail reinvestigation of the quasi-particle energy structure by means of the self-consistent GW approach allowed us to explain how p-type electrical conductivity can be engineered in the material.

  4. Research on the Interaction of Hydrogen-Bond Acidic Polymer Sensitive Sensor Materials with Chemical Warfare Agents Simulants by Inverse Gas Chromatography

    Directory of Open Access Journals (Sweden)

    Liu Yang

    2015-06-01

    Full Text Available Hydrogen-bond acidic polymers are important high affinity materials sensitive to organophosphates in the chemical warfare agent sensor detection process. Interactions between the sensor sensitive materials and chemical warfare agent simulants were studied by inverse gas chromatography. Hydrogen bonded acidic polymers, i.e., BSP3, were prepared for micro-packed columns to examine the interaction. DMMP (a nerve gas simulant and 2-CEES (a blister agent simulant were used as probes. Chemical and physical parameters such as heats of absorption and Henry constants of the polymers to DMMP and 2-CEES were determined by inverse gas chromatography. Details concerning absorption performance are also discussed in this paper.

  5. Research on the interaction of hydrogen-bond acidic polymer sensitive sensor materials with chemical warfare agents simulants by inverse gas chromatography.

    Science.gov (United States)

    Yang, Liu; Han, Qiang; Cao, Shuya; Huang, Feng; Qin, Molin; Guo, Chenghai; Ding, Mingyu

    2015-06-02

    Hydrogen-bond acidic polymers are important high affinity materials sensitive to organophosphates in the chemical warfare agent sensor detection process. Interactions between the sensor sensitive materials and chemical warfare agent simulants were studied by inverse gas chromatography. Hydrogen bonded acidic polymers, i.e., BSP3, were prepared for micro-packed columns to examine the interaction. DMMP (a nerve gas simulant) and 2-CEES (a blister agent simulant) were used as probes. Chemical and physical parameters such as heats of absorption and Henry constants of the polymers to DMMP and 2-CEES were determined by inverse gas chromatography. Details concerning absorption performance are also discussed in this paper.

  6. Chemically bonded hybrid systems from functionalized hydroxypyridine molecular bridge: characterization and photophysical properties.

    Science.gov (United States)

    Yan, Bing; Qian, Kai

    2009-01-01

    A series of novel photoactive hybrid materials with organic parts covalently linked to inorganic parts via the acylamino group have been assembled by sol-gel process. The organic parts as molecular bridge derive from alpha-hydroxypyridine (HP) functionalized by 3-(triethoxysilyl)-propyl isocyanate (TESPIC). Finally homogeneous, molecular-based hybrid materials with different microstructure (uniform spherical or clubbed) are obtained, in which no phase separation is observed. This may be ascribed as the different coordination behavior of metal ions (Eu3+ (Tb3+) or Zn2+). Red emission of Eu-HP-Si, green emission of Tb-HP-Si and violet-blue luminescence of Zn-HP-Si hybrids can be achieved within these molecular-based hybrid materials. Besides, both Eu(Tb) and Zn are introduced into the same hybrid systems (Eu(Zn)-HP-Si or Tb(Zn)-HP-Si) through the covalent Si-O bond, whose sphere particle size can be modified. Especially the photoluminescence behavior can be enhanced, suggesting that intramolecular energy transfer takes place between inert Zn2+ and Eu3+ (Tb3+) in the covalently bonded hybrid systems.

  7. Carbene→N⁺ Coordination Bonds in Drugs: A Quantum Chemical Study

    Indian Academy of Sciences (India)

    DEEPIKA KATHURIA; MINHAJUL ARFEEN; APOORVA A BANKAR; PRASAD V BHARATAM

    2016-10-01

    Coordination chemistry of bonds between main group elements and electron donating ligands as in L→E (where E is electron acceptor centre like C⁰, Si⁰, N¹, P¹, As¹, B¹ and L is an electron donating N-heterocyclic carbene) have been recently gaining attention. Many important drugs have nitrogen atom as an electron acceptor center and can be represented by two general formulae:(L→N←L)⊕ and L→N-R. Divalent N¹ compounds possess two lone pairs at central nitrogen and low nucleophilicity associated with them are found to be of importance. In this article, electronic structure analysis of drug molecules like picloxydine, chlorhexidine, and moroxydine were performed at B3LYP/6-311++G(d,p) level of theory. Evaluation of electron localization function (ELF), molecular orbitals, charge density, nucleophilicity, proton affinity and complexation energy estimation confirm the presence of coordination bonds (L→N←L)⊕ in the above mentioned drug molecules in their cationic state. Further, electronic structure analysis of drugs like clonidine, apraclonidine, brimonidine and xylazine indicated the presence of electronic structure similar to L→N-R systems.

  8. Chemical, modulus and cell attachment studies of reactive calcium phosphate filler-containing fast photo-curing, surface-degrading, polymeric bone adhesives.

    Science.gov (United States)

    Abou Neel, E A; Palmer, G; Knowles, J C; Salih, V; Young, A M

    2010-07-01

    The initial structure, setting and degradation processes of a poly(lactide-co-propylene glycol-co-lactide) dimethacrylate adhesive filled with 50, 60 or 70 wt.% reactive calcium phosphates (monocalcium phosphate monohydrate (MCPM)/beta-tricalcium phosphate (beta-TCP)) have been assessed using nuclear magnetic resonance, Fourier transform infrared spectroscopy, Raman, X-ray powder diffraction and gravimetric studies. Filler incorporation reduced the rapid light-activated monomer polymerization rates slightly, but not the final levels. Upon immersion in water for 24h, the set composite mass and volume increased due to water sorption. This promoted initial soluble MCPM loss from the composite surfaces, but also its reaction and monetite precipitation within the specimen bulk. After 48 h, composite gravimetric and chemical studies were consistent with surface erosion of polymer with reacted/remaining filler. The filled formulations exhibited more rapid early water sorption and subsequent surface erosion than the unfilled polymer. Calcium and phosphate release profiles and solution pH measurements confirmed early loss of surface MCPM with protons from polymer degradation products. At later times, the slower release of monetite/beta-TCP buffered composite storage solutions at approximately 5 instead of 3.2 for the unfilled polymer. Incorporation of filler increased both the early and later time material modulus. At intermediate times this effect was lost, presumably as a result of enhanced water sorption. The early modulus values obtained fell within the range reported for cancellous bone. Despite surface degradation, initial human mesenchymal cell attachment to both composites and polymer could be comparable with a non-degrading positive Thermanox control. These studies indicate that the filled formulations may be good candidates for bone repair. Release of calcium and phosphate ions provides components essential for such repair.

  9. Influence of physico-chemical material characteristics on staphylococcal biofilm formation – A qualitative and quantitative in vitro analysis of five different calcium phosphate bone grafts

    Directory of Open Access Journals (Sweden)

    M Clauss

    2014-07-01

    Full Text Available Various compositions of synthetic calcium phosphates (CaP have been proposed and their use has considerably increased over the past decades. Besides differences in physico-chemical properties, resorption and osseointegration, artificial CaP bone graft might differ in their resistance against biofilm formation. We investigated standardised cylinders of 5 different CaP bone grafts (cyclOS, chronOS (both β-TCP (tricalcium phosphate, dicalcium phosphate (DCP, calcium-deficient hydroxyapatite (CDHA and α-TCP. Various physico-chemical characterisations e.g., geometrical density, porosity, and specific surface area were investigated. Biofilm formation was carried out in tryptic soy broth (TSB and human serum (SE using Staphylococcus aureus (ATCC 29213 and S. epidermidis RP62A (ATCC 35984. The amount of biofilm was analysed by an established protocol using sonication and microcalorimetry. Physico-chemical characterisation showed marked differences concerning macro- and micropore size, specific surface area and porosity accessible to bacteria between the 5 scaffolds. Biofilm formation was found on all scaffolds and was comparable for α-TCP, chronOS, CDHA and DCP at corresponding time points when the scaffolds were incubated with the same germ and/or growth media, but much lower for cyclOS. This is peculiar because cyclOS had an intermediate porosity, mean pore size, specific surface area, and porosity accessible to bacteria. Our results suggest that biofilm formation is not influenced by a single physico-chemical parameter alone but is a multi-step process influenced by several factors in parallel. Transfer from in vitro data to clinical situations is difficult; thus, advocating the use of cyclOS scaffolds over the four other CaP bone grafts in clinical situations with a high risk of infection cannot be clearly supported based on our data.

  10. Influence of physico-chemical material characteristics on staphylococcal biofilm formation--a qualitative and quantitative in vitro analysis of five different calcium phosphate bone grafts.

    Science.gov (United States)

    Clauss, M; Furustrand Tafin, U; Betrisey, B; van Garderen, N; Trampuz, A; Ilchmann, T; Bohner, M

    2014-07-18

    Various compositions of synthetic calcium phosphates (CaP) have been proposed and their use has considerably increased over the past decades. Besides differences in physico-chemical properties, resorption and osseointegration, artificial CaP bone graft might differ in their resistance against biofilm formation. We investigated standardised cylinders of 5 different CaP bone grafts (cyclOS, chronOS (both β-TCP (tricalcium phosphate)), dicalcium phosphate (DCP), calcium-deficient hydroxyapatite (CDHA) and α-TCP). Various physico-chemical characterisations e.g., geometrical density, porosity, and specific surface area were investigated. Biofilm formation was carried out in tryptic soy broth (TSB) and human serum (SE) using Staphylococcus aureus (ATCC 29213) and S. epidermidis RP62A (ATCC 35984). The amount of biofilm was analysed by an established protocol using sonication and microcalorimetry. Physico-chemical characterisation showed marked differences concerning macro- and micropore size, specific surface area and porosity accessible to bacteria between the 5 scaffolds. Biofilm formation was found on all scaffolds and was comparable for α-TCP, chronOS, CDHA and DCP at corresponding time points when the scaffolds were incubated with the same germ and/or growth media, but much lower for cyclOS. This is peculiar because cyclOS had an intermediate porosity, mean pore size, specific surface area, and porosity accessible to bacteria. Our results suggest that biofilm formation is not influenced by a single physico-chemical parameter alone but is a multi-step process influenced by several factors in parallel. Transfer from in vitro data to clinical situations is difficult; thus, advocating the use of cyclOS scaffolds over the four other CaP bone grafts in clinical situations with a high risk of infection cannot be clearly supported based on our data.

  11. The mystery of gold's chemical activity: local bonding, morphology and reactivity of atomic oxygen.

    Science.gov (United States)

    Baker, Thomas A; Liu, Xiaoying; Friend, Cynthia M

    2011-01-07

    Recently, gold has been intensely studied as a catalyst for key synthetic reactions. Gold is an attractive catalyst because, surprisingly, it is highly active and very selective for partial oxidation processes suggesting promise for energy-efficient "green" chemistry. The underlying origin of the high activity of Au is a controversial subject since metallic gold is commonly thought to be inert. Herein, we establish that one origin of the high activity for gold catalysis is the extremely reactive nature of atomic oxygen bound in 3-fold coordination sites on metallic gold. This is the predominant form of O at low concentrations on the surface, which is a strong indication that it is most relevant to catalytic conditions. Atomic oxygen bound to metallic Au in 3-fold sites has high activity for CO oxidation, oxidation of olefins, and oxidative transformations of alcohols and amines. Among the factors identified as important in Au-O interaction are the morphology of the surface, the local binding site of oxygen, and the degree of order of the oxygen overlayer. In this Perspective, we present an overview of both theory and experiments that identify the reactive forms of O and their associated charge density distributions and bond strengths. We also analyze and model the release of Au atoms induced by O binding to the surface. This rough surface also has the potential for O(2) dissociation, which is a critical step if Au is to be activated catalytically. We further show the strong parallels between product distributions and reactivity for O-covered Au at low pressure (ultrahigh vacuum) and for nanoporous Au catalysts operating at atmospheric pressure as evidence that atomic O is the active species under working catalytic conditions when metallic Au is present. We briefly discuss the possible contributions of oxidants that may contain intact O-O bonds and of the Au-metal oxide support interface in Au catalysis. Finally, the challenges and future directions for fully

  12. Catalytic C-C Bond Cleavage for the Production of Chemicals from Lignin

    NARCIS (Netherlands)

    Jastrzebski, R.

    2016-01-01

    Lignin is a major component of lignocellulosic biomass and could be an important renewable feedstock in industry for the production of (aromatic) bulk and fine chemicals. To this end, the development of new catalytic processes is required; both to depolymerise the biopolymer into small aromatic buil

  13. Using Concept Mapping to Uncover Students' Knowledge Structures of Chemical Bonding Concepts

    Science.gov (United States)

    Burrows, Nikita L.; Mooring, Suazette Reid

    2015-01-01

    General chemistry is the first undergraduate course in which students further develop their understanding of fundamental chemical concepts. Many of these fundamental topics highlight the numerous conceptual interconnections present in chemistry. However, many students possess incoherent knowledge structures regarding these topics. Therefore,…

  14. Finite Size Effects in Chemical Bonding: From Small Clusters to Solids

    DEFF Research Database (Denmark)

    Kleis, Jesper; Greeley, Jeffrey Philip; Romero, N. A.;

    2011-01-01

    We address the fundamental question of which size a metallic nano-particle needs to have before its surface chemical properties can be considered to be those of a solid, rather than those of a large molecule. Calculations of adsorption energies for carbon monoxide and oxygen on a series of gold...

  15. Thermal-mechanical-chemical responses of polymer-bonded explosives using a mesoscopic reactive model under impact loading.

    Science.gov (United States)

    Wang, XinJie; Wu, YanQing; Huang, FengLei

    2017-01-05

    A mesoscopic framework is developed to quantify the thermal-mechanical-chemical responses of polymer-bonded explosive (PBX) samples under impact loading. A mesoscopic reactive model is developed for the cyclotetramethylenetetranitramine (HMX) crystal, which incorporates nonlinear elasticity, crystal plasticity, and temperature-dependent chemical reaction. The proposed model was implemented in the finite element code ABAQUS by the user subroutine VUMAT. A series of three-dimensional mesoscale models were constructed and calculated under low-strength impact loading scenarios from 100m/s to 600m/s where only the first wave transit is studied. Crystal anisotropy and microstructural heterogeneity are responsible for the nonuniform stress field and fluctuations of the stress wave front. At a critical impact velocity (≥300m/s), a chemical reaction is triggered because the temperature contributed by the volumetric and plastic works is sufficiently high. Physical quantities, including stress, temperature, and extent of reaction, are homogenized from those across the microstructure at the mesoscale to compare with macroscale measurements, which will advance the continuum-level models. The framework presented in this study has important implications in understanding hot spot ignition processes and improving predictive capabilities in energetic materials.

  16. Electronic parameters of Sr2M2O7 (M = V, Nb, Ta) and Sr-O chemical bonding

    DEFF Research Database (Denmark)

    Atuchin, Victor V.; Grivel, Jean-Claude; Zhang, Zhaoming

    2010-01-01

    on the formation of the Sr-O bonds. The chemical bonding effects were considered on the basis of our XPS results for Sr2Nb2O7 and Sr2Ta2O7 and the previously published structural and XPS data for other Sr-oxide compounds. A new empirical relationship between Δ(O-Sr) and L(Sr-O) was obtained. Possible applications...

  17. Study of the irradiation effects on thorium phosphate diphosphate ({beta}-TPD): consequences on its chemical durability; Etude des effets d'irradiation sur le phosphate diphosphate de thorium ({beta}-PDT): consequences sur la durabilite chimique

    Energy Technology Data Exchange (ETDEWEB)

    Tamain, C

    2005-12-15

    Since Thorium Phosphate Diphosphate (beta-TPD) can be considered as a potential host matrix for long-term storage in underground repository, it is necessary to study the irradiation effects on the structure of this ceramics and the consequences on its chemical durability. Sintered samples of beta-TPD and of associated solid solutions of beta-TUPD were irradiated under ion beams and then altered in aqueous solutions. Depending on the electronic LET value, beta-TPD can be completely or partly amorphized. Furthermore, the ability of recrystallization of the amorphous material by thermal annealing was also demonstrated. Some leaching tests, realized on these irradiated samples, have shown a significant effect of the amorphous fraction on the normalized dissolution rate which was increased by a factor of 10 from the crystallized to the fully amorphized material. Correlatively, the amorphous fraction also modified the delay to reach the saturation conditions associated to the thermodynamic equilibria involved. On the other hand, it exhibited no influence neither on other kinetic parameters, such as activation energy of the dissolution process or partial order related to the proton concentration, nor on the nature of the neo-formed phase formed at the saturation of the leachate and identified as Thorium Phosphate Hydrogeno-Phosphate Hydrate (TPHPH). Beta-TUPD samples were also irradiated by gamma and alpha rays during leaching tests to study the effects of radiolysis in the leaching medium on the normalized leaching rate. It appeared that the radiolytic species occurring in the dissolution mechanism were unstable, disappearing quickly when stopping the irradiation. (author)

  18. Magnetovolume and chemical bonding effects of Sn atom in the γ'-(Fe1-xSnx)4N compounds

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Combining x-ray diffraction and high pressure Mossbauer spectroscopy,the structure and the hyperfine parameters of Sn substituted for Fe in γ'-Fe4N were in-vestigated. The results of x-ray diffraction indicate that single phase γ'-(Fel-xSnx)4Ncompounds can be synthesized in the composition range 0≤ x ≤ 0.3, and the latticeparameter can be well fitted with two linear formulas α0(x) = 3.795 + 0.019 × x (0.0≤x ≤0.10) and α0(x) = 3.795+ 0.228 × (x- 0.1)(0.10 ≤ x ≤0.30) for different contentof Sn. Using high pressure Mossbauer spectra, the influences of the magnetovolunceffect and the chemical bonding effect of Sn atom on the hyperfine magnetic field andthe isomer shift were first distinguished. It is found that the magnetovolume and thechemical bonding have different influences on the properties of γ'-(Fe1-xSnx)4N, andthe latter plays a more important role.

  19. Mechanical control of the plasmon coupling with Au nanoparticle arrays fixed on the elastomeric film via chemical bond

    Science.gov (United States)

    Bedogni, Elena; Kaneko, Satoshi; Fujii, Shintaro; Kiguchi, Manabu

    2017-03-01

    We have fabricated Au nanoparticle arrays on the flexible poly(dimethylsiloxane) (PDMS) film. The nanoparticles were bound to the film via a covalent bond by a ligand exchange reaction. Thanks to the strong chemical bonding, highly stable and uniformly dispersed Au nanoparticle arrays were fixed on the PDMS film. The Au nanoparticle arrays were characterized by the UV–vis, scanning electron microscope (SEM) and surface enhanced Raman scattering (SERS). The UV–vis and SEM measurements showed the uniformity of the surface-dispersed Au nanoparticles, and SERS measurement confirmed the chemistry of the PDMS film. Reflecting the high stability and the uniformity of the Au nanoparticle arrays, the plasmon wavelength of the Au nanoparticles reversely changed with modulation of the interparticle distance, which was induced by the stretching of the PDMS film. The plasmon wavelength linearly decreased from 664 to 591 nm by stretching of 60%. The plasmon wavelength shift can be explained by the change in the strength of the plasmon coupling which is mechanically controlled by the mechanical strain.

  20. Evidence for excited-state intramolecular proton transfer in 4-chlorosalicylic acid from combined experimental and computational studies: Quantum chemical treatment of the intramolecular hydrogen bonding interaction

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Bijan Kumar [Department of Chemistry, University of Calcutta, 92 Acharya Prafulla Chandra Road, Calcutta 700009 (India); Guchhait, Nikhil, E-mail: nikhil.guchhait@rediffmail.com [Department of Chemistry, University of Calcutta, 92 Acharya Prafulla Chandra Road, Calcutta 700009 (India)

    2012-07-25

    Highlights: Black-Right-Pointing-Pointer Experimental and computational studies on the photophysics of 4-chlorosalicylic acid. Black-Right-Pointing-Pointer Spectroscopically established ESIPT reaction substantiated by theoretical calculation. Black-Right-Pointing-Pointer Quantum chemical treatment of IMHB unveils strength, nature and directional nature. Black-Right-Pointing-Pointer Superiority of quantum chemical treatment of H-bond over geometric criteria. Black-Right-Pointing-Pointer Role of H-bond as a modulator of aromaticity. -- Abstract: The photophysical study of a pharmaceutically important chlorine substituted derivative of salicylic acid viz., 4-chlorosalicylic acid (4ClSA) has been carried out by steady-state absorption, emission and time-resolved emission spectroscopy. A large Stokes shifted emission band with negligible solvent polarity dependence marks the spectroscopic signature of excited-state intramolecular proton transfer (ESIPT) reaction in 4ClSA. Theoretical calculation by ab initio and Density Functional Theory methods yields results consistent with experimental findings. Theoretical potential energy surfaces predict the occurrence of proton transfer in S{sub 1}-state. Geometrical and energetic criteria, Atoms-In-Molecule topological parameters, Natural Bond Orbital population analysis have been exploited to evaluate the intramolecular hydrogen bond (IMHB) interaction and to explore its directional nature. The inter-correlation between aromaticity and resonance assisted H-bond is also discussed in this context. Our results unveil that the quantum chemical treatment is a more accurate tool to assess hydrogen bonding interaction in comparison to geometrical criteria.

  1. Robust C-C bonded porous networks with chemically designed functionalities for improved CO2 capture from flue gas.

    Science.gov (United States)

    Thirion, Damien; Lee, Joo S; Özdemir, Ercan; Yavuz, Cafer T

    2016-01-01

    Effective carbon dioxide (CO2) capture requires solid, porous sorbents with chemically and thermally stable frameworks. Herein, we report two new carbon-carbon bonded porous networks that were synthesized through metal-free Knoevenagel nitrile-aldol condensation, namely the covalent organic polymer, COP-156 and 157. COP-156, due to high specific surface area (650 m(2)/g) and easily interchangeable nitrile groups, was modified post-synthetically into free amine- or amidoxime-containing networks. The modified COP-156-amine showed fast and increased CO2 uptake under simulated moist flue gas conditions compared to the starting network and usual industrial CO2 solvents, reaching up to 7.8 wt % uptake at 40 °C.

  2. Robust C–C bonded porous networks with chemically designed functionalities for improved CO2 capture from flue gas

    Science.gov (United States)

    Thirion, Damien; Lee, Joo S; Özdemir, Ercan

    2016-01-01

    Effective carbon dioxide (CO2) capture requires solid, porous sorbents with chemically and thermally stable frameworks. Herein, we report two new carbon–carbon bonded porous networks that were synthesized through metal-free Knoevenagel nitrile–aldol condensation, namely the covalent organic polymer, COP-156 and 157. COP-156, due to high specific surface area (650 m2/g) and easily interchangeable nitrile groups, was modified post-synthetically into free amine- or amidoxime-containing networks. The modified COP-156-amine showed fast and increased CO2 uptake under simulated moist flue gas conditions compared to the starting network and usual industrial CO2 solvents, reaching up to 7.8 wt % uptake at 40 °C. PMID:28144294

  3. Electronic structure, chemical bond and thermal stability of hydrogen absorber Li2MgN2H2

    Institute of Scientific and Technical Information of China (English)

    WANG Qiang; CHEN YunGui; WU ChaoLing; TAO MingDa; GAI JingGang

    2009-01-01

    The lowest total energy crystal structure of Li2MgN2H2 was identified by the first principle calculation with RPBE exchange-correlation function. Furthermore, the fine structure parameters of this crystal structure were calculated with PBE and PW91 exchange-correlation function. In a further step, the density of states, electron density, charge density difference on (0 0 1) plane and heat of formation of Li2MgN2H2 hydrogenation were computed with PW91 exchange-correlation function. Consequently, the electronic structures and chemical bonds in this compound were analyzed and discussed, and then the thermodynamic character of Li2MgN2H2 for hydrogen storage was evacuated.

  4. Evidence for porphyrins bound, via ester bonds, to the Messel oil shale kerogen by selective chemical degradation experiments

    Science.gov (United States)

    Huseby, B.; Ocampo, R.

    1997-09-01

    High amounts of nickel mono- and di-acid porphyrins were released from Messel oil shale kerogen (Eocene, Germany) by selective chemical degradation (acid and base hydrolysis). The released porphyrin fractions were quantified (UV-vis) and their constituents isolated and characterized at the molecular level (UV-vis, MS, NMR). The mono-acid porphyrin fraction released contained four compounds of similar abundance which arise from an obvious chlorophyll or bacteriochlorophyll precursor. The di-acid porphyrin fraction was, however, dominated by far by one compound, mesoporphyrin IX, which must have originated from heme-like precursors (heme, cytochromes, etc.). These results show unambigously that the released mono- and di-acid porphyrins were linked to the macromolecular kerogen network via ester bonds and suggest that precursor heme-like pigments could be selectively and/or more readily incorporated into the macromolecular kerogen network than precursor chlorophylls and bacteriochlorophylls.

  5. Effects of lithium doping on microstructure, electrical properties, and chemical bonds of sol-gel derived NKN thin films

    Science.gov (United States)

    Lin, Chun-Cheng; Chen, Chan-Ching; Weng, Chung-Ming; Chu, Sheng-Yuan; Hong, Cheng-Shong; Tsai, Cheng-Che

    2015-02-01

    Highly (100/110) oriented lead-free Lix(Na0.5K0.5)1-xNbO3 (LNKN, x = 0, 0.02, 0.04, and 0.06) thin films are fabricated on Pt/Ti/SiO2/Si substrates via a sol-gel processing method. The lithium (Li) dopants modify the microstructure and chemical bonds of the LNKN films, and therefore improve their electrical properties. The optimal values of the remnant polarization (Pr = 14.3 μC/cm2), piezoelectric coefficient (d33 = 48.1 pm/V), and leakage current (Poole-Frenkel emission effect under high electric fields.

  6. Immobilization of fission products in phosphate ceramic waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Singh, D.; Wagh, A. [Argonne National Lab., IL (United States)

    1997-10-01

    Chemically bonded phosphate ceramics (CBPCs) have several advantages that make them ideal candidates for containing radioactive and hazardous wastes. In general, phosphates have high solid-solution capacities for incorporating radionuclides, as evidenced by several phosphates (e.g., monazites and apatites) that are natural analogs of radioactive and rare-earth elements. The phosphates have high radiation stability, are refractory, and will not degrade in the presence of internal heating by fission products. Dense and hard CBPCs can be fabricated inexpensively and at low temperature by acid-base reactions between an inorganic oxide/hydroxide powder and either phosphoric acid or an acid-phosphate solution. The resulting phosphates are extremely insoluble in aqueous media and have excellent long-term durability. CBPCs offer the dual stabilization mechanisms of chemical fixation and physical encapsulation, resulting in superior waste forms. The goal of this task is develop and demonstrate the feasibility of CBPCs for S/S of wastes containing fission products. The focus of this work is to develop a low-temperature CBPC immobilization system for eluted {sup 99}Tc wastes from sorption processes.

  7. Investigation of finite-size effects in chemical bonding of AuPd nanoalloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Beien [Division of Interfacial Water and Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Oğuz, Ismail Can; Guesmi, Hazar, E-mail: hazar.guesmi@enscm.fr [CNRS-ICG UMR 5253, équipe MACS, 8 rue de l’Ecole Normale, 34296 Montpellier (France)

    2015-10-14

    In this paper, the size-dependent changes in energetic, vibrational, and electronic properties of C–O gas molecule interacting with surface Pd atom of a variety of AuPd nanoalloy structures are investigated by means of first principles calculations. The variation in C–O adsorption energies, C–O vibration frequencies (ν{sub C−O}), and Pd d-bond centers (ε{sub d}) on a series of non-supported Au{sub n−1}–Pd{sub 1} nanoparticles (with n varying from 13 to 147) and on two semi-finite surfaces are inspected with cluster size. We demonstrate for the first time that, with small AuPd bimetallic three-dimensional clusters as TOh{sub 38}, one can reach cluster size convergence even for such a sensitive observable as the adsorption energy on a metal surface. Indeed, the results show that the adsorbate-induced perturbation is extremely local and it only concerns the isolated Pd interacting with the reactive gas molecule. Except for 13 atom clusters, in which molecular behaviour is predominant, no finite-size effects are observed for surface Pd atom substituted in AuPd free nanoclusters above 38 atoms.

  8. Crystal structure and chemical bonding of the high-temperature phase of AgN3.

    Science.gov (United States)

    Schmidt, Carsten L; Dinnebier, Robert; Wedig, Ulrich; Jansen, Martin

    2007-02-05

    The crystal structure of silver azide (AgN3) in its high-temperature (HT) modification was determined from X-ray powder diffraction data, recorded at T = 170 degrees C and was further refined by the Rietveld method. The structure is monoclinic (P21/c (No. 14), a = 6.0756(2) A, b = 6.1663(2) A, c = 6.5729(2) A, beta = 114.19(0) degrees, V = 224.62(14) A3, Z = 4) and consists of two-dimensional Ag and N containing layers in which the silver atoms are coordinated by four nitrogen atoms exhibiting a distorted square coordination environment. These sheets are linked together by weaker perpendicular Ag-N contacts, thus forming a 4 + 2 coordination geometry around the silver atoms. The phase transition has been characterized by DTA, DSC, and measurement of the density, as well as of the ionic conductivity. Both, the room-temperature and the HT phase are electrically insulating. This fact is getting support by DFT band structure calculations within the generalized gradient approximation, using the PBE functional. On the basis of the DFT band structure, the bonding characteristics of both phases are essentially the same. Finally, the implication of the existence of a low-symmetry HT-phase in a crystalline explosive concerning decomposition mechanisms is discussed.

  9. Crystal Structure and Chemical Bonding of the High-Temperature Phase of AgN3

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt,C.; Dinnebier, R.; Wedig, U.; Jansen, M.

    2007-01-01

    The crystal structure of silver azide (AgN{sub 3}) in its high-temperature (HT) modification was determined from X-ray powder diffraction data, recorded at T = 170 {sup o}C and was further refined by the Rietveld method. The structure is monoclinic (P2{sub 1}lc (No. 14), a = 6.0756(2) {angstrom}, b = 6.1663(2) {angstrom}, c = 6.5729(2) {angstrom}, {beta} = 114.19(0){sup o}, V = 224.62(14) {angstrom}{sup 3}, Z = 4) and consists of two-dimensional Ag and N containing layers in which the silver atoms are coordinated by four nitrogen atoms exhibiting a distorted square coordination environment. These sheets are linked together by weaker perpendicular Ag-N contacts, thus forming a 4 + 2 coordination geometry around the silver atoms. The phase transition has been characterized by DTA, DSC, and measurement of the density, as well as of the ionic conductivity. Both, the room-temperature and the HT phase are electrically insulating. This fact is getting support by DFT band structure calculations within the generalized gradient approximation, using the PBE functional. On the basis of the DFT band structure, the bonding characteristics of both phases are essentially the same. Finally, the implication of the existence of a low-symmetry HT-phase in a crystalline explosive concerning decomposition mechanisms is discussed.

  10. Surface chemical-bonds analysis of silicon particles from diamond-wire cutting of crystalline silicon

    Science.gov (United States)

    Benayad, Anass; Hajjaji, Hamza; Coustier, Fabrice; Benmansour, Malek; Chabli, Amal

    2016-12-01

    The recycling of the Si powder resulting from the kerf loss during silicon ingot cutting into wafers for photovoltaic application shows both significant and achievable economic and environmental benefits. A combined x-ray photoelectron spectroscopy (XPS), attenuated total reflection (ATR)-Fourier transform infrared (FTIR) and micro-Raman spectral analyses were applied to kerf-loss Si powders reclaimed from the diamond wire cutting using different cutting fluids. These spectroscopies performed in suitable configurations for the analysis of particles, yield detailed insights on the surface chemical properties of the powders demonstrating the key role of the cutting fluid nature. A combined XPS core peak, plasmon loss, and valence band study allow assessing a qualitative and quantitative chemical, structural change of the kerf-loss Si powders. The relative contribution of the LO and TO stretching modes to the Si-O-Si absorption band in the ATR-FTIR spectra provide a consistent estimation of the effective oxidation level of the Si powders. The change in the cutting media from deionized water to city water, induces a different silicon oxide layer thickness at the surface of the final kerf-loss Si, depending on the powder reactivity to the media. The surfactant addition induces an enhanced carbon contamination in the form of grafted carbonated species on the surface of the particles. The thickness of the modified surface, depending on the cutting media, was estimated based on a simple model derived from the combined XPS core level and plasmon peak intensities. The effective nature of these carbonated species, sensitive to the water quality, was evidenced based on coupled XPS core peak and valence band study. The present work paves the way to a controlled process to reclaim the kerf-loss Si powder without heavy chemical etching steps.

  11. FONO: a difficult case for theory. The ELF and ELI-D topological studies on the chemical bonding using correlated wavefunctions.

    Science.gov (United States)

    Berski, Slawomir; Gordon, Agnieszka J; Latajka, Zdzislaw

    2013-04-01

    The complicated nature of the chemical bonding in cis and trans isomers of F-O-N=O is discussed based on the results obtained from the topological analysis of electron localization function (η) (ELF), electron localizability index (Y(D)(σ)), and electron density (ρ). The calculations have been performed for correlated wavefunctions using the CCSD and CASSCF methods. The F-O1 bond with non-bonding basins, V(F) and V(')(O1), belongs to the protocovalent type (η,Y(D)(σ)) and its total population ranges between 0.2 and 0.4e. The central N-O1 bond in the cis form is protocovalent (η, Y(D)(σ)) with two basins, V(N) and V(O1). The total population oscillates between 0.7 and 0.9e. In the trans isomer, topology of ELF depends on used method. At the CCSD level only one non-bonding basin, V(N), is observed (η). Its population is about 0.5e. According to the definition of a heteronuclear charge-shift (CS) bond, only N-O1 bond in trans-FONO belongs to the CS class. A relation between η- and ρ-topology and N-O1 bond length is discussed.

  12. The enzymatic conversion of phosphonates to phosphate by bacteria.

    Science.gov (United States)

    Kamat, Siddhesh S; Raushel, Frank M

    2013-08-01

    Phosphonates are ubiquitous organophosphorus compounds that contain a characteristic CP bond which is chemically inert and hydrolytically stable. Bacteria have evolved pathways to metabolize these phosphonate compounds and utilize the products of these pathways as nutrient sources. This review aims to present all of the known bacterial enzymes capable of transforming phosphonates to phosphates. There are three major classes of enzymes known to date performing such transformations: phosphonatases, the C-P lyase complex and an oxidative pathway for CP bond cleavage. A brief description of each class is presented.

  13. Synthesis, vibrational and quantum chemical investigations of hydrogen bonded complex betaine dihydrogen selenite

    Science.gov (United States)

    Arjunan, V.; Marchewka, Mariusz K.; Kalaivani, M.

    2012-10-01

    The molecular complex of betaine with selenious acid namely, betaine dihydrogen selenite (C5H13NO5Se, BDHSe) was synthesised by the reaction of betaine and SeO2 in a 1:1:1 solution of isopropanol, methanol and water. Crystals were grown from this solution by cooling to 253 K for few days. The complex was formed without accompanying proton transfer from selenious acid molecule to betaine. The complete vibrational assignments and analysis of BDHSe have been performed by FTIR, FT-Raman and far-infrared spectral studies. More support on the experimental findings was added from the quantum chemical studies performed with DFT (B3LYP) method using 6-311++G∗∗, 6-31G∗∗, cc-pVDZ and 3-21G basis sets. The structural parameters, energies, thermodynamic parameters and the NBO charges of BDHSe were determined by the DFT method. The 1H and 13C isotropic chemical shifts (δ ppm) of BDHSe with respect to TMS were also calculated using the gauge independent atomic orbital (GIAO) method and compared with the experimental data. SHG experiment was carried out using Kurtz-Perry powder technique. The efficiency of second harmonic generation for BDHSe was estimated relatively to KDP: deff = 0.97 deff (KDP).

  14. Synthesis, vibrational and quantum chemical investigations of hydrogen bonded complex betaine dihydrogen selenite.

    Science.gov (United States)

    Arjunan, V; Marchewka, Mariusz K; Kalaivani, M

    2012-10-01

    The molecular complex of betaine with selenious acid namely, betaine dihydrogen selenite (C(5)H(13)NO(5)Se, BDHSe) was synthesised by the reaction of betaine and SeO(2) in a 1:1:1 solution of isopropanol, methanol and water. Crystals were grown from this solution by cooling to 253 K for few days. The complex was formed without accompanying proton transfer from selenious acid molecule to betaine. The complete vibrational assignments and analysis of BDHSe have been performed by FTIR, FT-Raman and far-infrared spectral studies. More support on the experimental findings was added from the quantum chemical studies performed with DFT (B3LYP) method using 6-311++G(**), 6-31G(**), cc-pVDZ and 3-21G basis sets. The structural parameters, energies, thermodynamic parameters and the NBO charges of BDHSe were determined by the DFT method. The (1)H and (13)C isotropic chemical shifts (δ ppm) of BDHSe with respect to TMS were also calculated using the gauge independent atomic orbital (GIAO) method and compared with the experimental data. SHG experiment was carried out using Kurtz-Perry powder technique. The efficiency of second harmonic generation for BDHSe was estimated relatively to KDP: d(eff)=0.97 d(eff) (KDP).

  15. Research Update: Mechanical properties of metal-organic frameworks – Influence of structure and chemical bonding

    Directory of Open Access Journals (Sweden)

    Wei Li

    2014-12-01

    Full Text Available Metal-organic frameworks (MOFs, a young family of functional materials, have been attracting considerable attention from the chemistry, materials science, and physics communities. In the light of their potential applications in industry and technology, the fundamental mechanical properties of MOFs, which are of critical importance for manufacturing, processing, and performance, need to be addressed and understood. It has been widely accepted that the framework topology, which describes the overall connectivity pattern of the MOF building units, is of vital importance for the mechanical properties. However, recent advances in the area of MOF mechanics reveal that chemistry plays a major role as well. From the viewpoint of materials science, a deep understanding of the influence of chemical effects on MOF mechanics is not only highly desirable for the development of novel functional materials with targeted mechanical response, but also for a better understanding of important properties such as structural flexibility and framework breathing. The present work discusses the intrinsic connection between chemical effects and the mechanical behavior of MOFs through a number of prototypical examples.

  16. Rationalizing structure, stability, and chemical bonding of pure and doped clusters, isolated and solvated multiply charged anions, and solid-state materials

    Science.gov (United States)

    Sergeeva, Alina P.

    Chemistry is the study of materials and the changes that materials undergo. One can tune the properties of the known materials and design the novel materials with desired properties knowing what is responsible for the chemical reactivity, structure, and stability of those materials. The unified chemical bonding theory could address all these questions, but we do not have one available yet. The most accepted general theory of chemical bonding was proposed by Lewis in 1916, though Lewis's theory fails to explain the bonding in materials with delocalized electron density such as sub-nano and nanoclusters, as well as aromatic organic and organometallic molecules. The dissertation presents a set of projects that can be considered the steps towards the development of the unified chemical bonding theory by extending the ideas of Lewis. The dissertation also presents the studies of the properties of multiply charged anions, which tend to undergo Coulomb explosion in the isolated state and release the excess energy stored in them. It is shown how the properties of multiply charged anions can be tuned upon changing the chemical identity of the species or interaction with solvent molecules. Our findings led to the discovery of a new long-lived triply charged anionic species, whose metastability was explained by the existence of a repulsive Coulomb barrier. We also proposed two ways to restore high symmetry of compounds by suppression of the pseudo Jahn-Teller effect, which could lead to the design of new materials with the restored symmetry and therefore the novel properties.

  17. Immobilization of TiO2 nanoparticles in polymeric substrates by chemical bonding for multi-cycle photodegradation of organic pollutants.

    Science.gov (United States)

    Lei, Ping; Wang, Feng; Gao, Xiaowei; Ding, Yanfen; Zhang, Shimin; Zhao, Jincai; Liu, Shaoren; Yang, Mingshu

    2012-08-15

    Nano titanium dioxide (TiO(2)) photocatalyst is generally immobilized onto the matrix through the physical absorption, hydrogen bonding or chemical bonding, which is utilized for the application of wastewater treatment. In this research, TiO(2) nanoparticles were immobilized in polyvinyl alcohol (PVA) matrix via solution-casting combined with heat-treatment method. Structure characterization indicated that Ti-O-C chemical bond formed via dehydration reaction between TiO(2) and PVA during the heat treatment process, and TiO(2) nanoparticles had been chemically immobilized in PVA matrix. Photodegradation results of methyl orange (MO) showed that the film with 10 wt% TiO(2) and treated at 140°C for 2h exhibited a remarkable ultraviolet (UV) photocatalytic activity, approximately close to the TiO(2) slurry system. This was mainly attributed to the fixation effect by Ti-O-C chemical bonds, which was indirectly confirmed by the slight loss of TiO(2) photocatalysts even after 25-cycle use. In addition, the good swelling ability of PVA matrix provided the MO molecules with more opportunities to fully contact with TiO(2), thus benefited the photocatalysis. This route to chemically immobilize TiO(2) nanoparticles is simple and cheap to prepare polymer/TiO(2) hybrid materials with high photocatalytic activity for multi-cycle use, which is of significance to the practical application of TiO(2) catalysts.

  18. Correlation between topological band character and chemical bonding in a Bi14Rh3I9-based family of insulators

    Science.gov (United States)

    Rasche, Bertold; Isaeva, Anna; Ruck, Michael; Koepernik, Klaus; Richter, Manuel; van den Brink, Jeroen

    2016-02-01

    Recently the presence of topologically protected edge-states in Bi14Rh3I9 was confirmed by scanning tunnelling microscopy consolidating this compound as a weak 3D topological insulator (TI). Here, we present a density-functional-theory-based study on a family of TIs derived from the Bi14Rh3I9 parent structure via substitution of Ru, Pd, Os, Ir and Pt for Rh. Comparative analysis of the band-structures throughout the entire series is done by means of a unified minimalistic tight-binding model that evinces strong similarity between the quantum-spin-Hall (QSH) layer in Bi14Rh3I9 and graphene in terms of -molecular orbitals. Topologically non-trivial energy gaps are found for the Ir-, Rh-, Pt- and Pd-based systems, whereas the Os- and Ru-systems remain trivial. Furthermore, the energy position of the metal -band centre is identified as the parameter which governs the evolution of the topological character of the band structure through the whole family of TIs. The -band position is shown to correlate with the chemical bonding within the QSH layers, thus revealing how the chemical nature of the constituents affects the topological band character.

  19. Surfactant free synthesis of CdS nanospheres, microstructural analysis, chemical bonding, optical properties and photocatalytic activities

    Science.gov (United States)

    Ganesh, R. Sankar; Sharma, Sanjeev K.; Durgadevi, E.; Navaneethan, M.; Binitha, H. S.; Ponnusamy, S.; Muthamizhchelvan, C.; Hayakawa, Y.; Kim, Deuk Young

    2017-04-01

    The surfactant free cadmium sulfide (CdS) nanospheres were synthesized by the chemical method in a single step. The uniform shape of CdS spheres was controlled by the variation of concentration of thioacetamide (C2H5NS). The cubic phase of CdS nanopowder was determined from XRD analysis, which closely matched to the standard card. The spherical grains of CdS powder were confirmed from the microstructural analysis. The concentration of thioacetamide (TAA) played a vital role in the formation of nanospheres. The bandgap of CdS nanospheres decreased from 2.44 to 2.22 eV as the mole concentration of C2H5NS increased from 0.05 M to 2.0 M. FTIR spectra confirmed the presence of the stretching bond of Cdsbnd S. The dominant PL peak of purely and uniformed CdS nanospheres was observed at 528 nm due to S vacancies or surface defects. The prepared photocatalyst demonstrated the superior visible light photocatalytic degradation of methylene blue (MB). The highest degradation (96%) of MB was achieved within 180 min. Therefore, CdS nanospheres grown in the single step by the chemical method has a remarkable enhancement in the degradation of pollutants under irradiation of visible light.

  20. Physio-chemical Investigation and Natural Bond Orbital Analysis of the Most Actives Ingredient of Fennel Plant

    Directory of Open Access Journals (Sweden)

    Mansoureh Pishehabadi

    2016-10-01

    Full Text Available In this study, physio-chemical properties of effective compounds of fennel plant were investigated through using computational chemistry. To do this, trans-anethole, estragole, 3'- hydroxyanethole and 4- methoxycinnamyl alcohol compounds that the most active ingredient combinations make up the fennel plant have been carried out at three different levels of HF, BLYP and B3LYP theories using 6-31G*, 6-311G*, 6-311G**, 6-311+G and 6-311++G basis sets. Additionally, ab initio calculation in the gas phase have been studied and physio-chemical parameters including Gibbs free energy, thermal energy, enthalpy, entropy, and thermal capacity in constant volume (CV of these compounds have been computed as well as Gibbs free energy in polar solvents such as ethanol and methanol and water. Based on these obtained data the structural stabilities of these flavorful compounds have been discussed. However, in these herbal effective compounds presented here the natural bond orbital (NBO analysis has been performed which seemed quite informative to show some important atomic and structural features. The result lead to the issue that all those compounds in polar solvents, particularly alcoholic solvents solved and the compounds can be used sufficiently to extract the active ingredients of herb fennel.

  1. Effect of conditioning methods on the microtensile bond strength of phosphate monomer-based cement on zirconia ceramic in dry and aged conditions

    NARCIS (Netherlands)

    Amaral, Regina; Ozcan, Mutlu; Valandro, Luiz Felipe; Balducci, Ivan; Bottino, Marco Antonio

    2008-01-01

    The objective of this study was to evaluate the durability of bond strength between a resin cement and aluminous ceramic submitted to various surface conditioning methods. Twenty-four blocks (5 X 5 X 4 mm 3) of a glass-in filtrated zirconia-alumina ceramic (inCeram Zirconia Classic) were randomly di

  2. Bio-chemical process for nitrogen and phosphorus removal by draining out anaerobic rich phosphate supernatant in ERP-SBR system

    Institute of Scientific and Technical Information of China (English)

    JIFangying; XUXiaoyi; LUOGuyuan

    2003-01-01

    The method of fixed phosphate coming from anaerobic reactor by the auxiliary chemical process is applied in External Recycle Process-SBR (ERP-SBR). This process changes the model of draining out activated sludge in the traditional biological phosphorus removal system to discharge anaerobic poly-phosphate supernatant. This process eliminates the contradiction of control for Solid Removal Time (SRT) in process of biological nitrogen and phosphorus removal. It can obtain high removal efficiency of nitrogen(N) and phosphorus(P) in longer SRT. Experiment results show that: when SRT=50 ~ 80 d, TN=28.6~ 58.3 mg/L, TP=5.5~ 13.5 mg/L in influent, COD≤ 34mg/L, TN≤ 6.02 mg/L, PO43-≤0.23 mg/L in effluent. The amount of lime is only 5% of traditional methods. The phosphorus content in the chemical sludge is 12 %~15 % and the recycle of phosphorus can be realized easily.

  3. Bond-length analysis of the omega structure in Ti,Zr,Hf and their alloys: experimental data, new correlations and implications for chemical bonding models

    Energy Technology Data Exchange (ETDEWEB)

    Grad, G.B.; Benites, G.M. [Comision Nacional de Energia Atomica, San Carlos de Bariloche (Argentina). Centro Atomico Bariloche; Aurelio, G. [Departamento de Fisica, Universidad del Comahue, 8300, Neuquen (Argentina); Fernandez Guillermet, A. [Centro Atomico Bariloche, 8400, San Carlos de Bariloche (Argentina)

    1999-12-15

    An analysis is performed of the experimental information on the key interatomic distances (IDs) of the AlB{sub 2} type structure, the so-called omega ({omega}) phase in Ti and Zr, as well as in Ti-V and Zr-Nb alloys. Various remarkable correlations are found between these IDs and standard measures of the atomic size, and with Pauling's bond-lengths. These observations are discussed in the light of the phenomenological bonding pictures of the {omega} structure, and with our recent ab initio calculations of the electronic structure of this phase. (orig.)

  4. Dilemmas in zirconia bonding: A review

    Directory of Open Access Journals (Sweden)

    Obradović-Đuričić Kosovka

    2013-01-01

    Full Text Available This article presents a literature review on the resin bond to zirconia ceramic. Modern esthetic dentistry has highly recognized zirconia, among other ceramic materials. Biocompatibility of zirconia, chemical and dimensional stability, excellent mechanical properties, all together could guarantee optimal therapeutical results in complex prosthodontic reconstruction. On the other hand, low thermal degradation, aging of zirconia as well as problematic bonding of zirconia framework to dental luting cements and tooth structures, opened the room for discussion concerning their clinical durability. The well known methods of mechanical and chemical bonding used on glass-ceramics are not applicable for use with zirconia. Therefore, under critical clinical situations, selection of the bonding mechanism should be focused on two important points: high initial bond strength value and long term bond strength between zirconia-resin interface. Also, this paper emphases the use of phosphate monomer luting cements on freshly air-abraded zirconia as the simplest and most effective way for zirconia cementation procedure today.

  5. Evolution of chemical bonding and electron density rearrangements during D(3h) → D(3d) reaction in monolayered TiS2: a QTAIM and ELF study.

    Science.gov (United States)

    Ryzhikov, Maxim R; Slepkov, Vladimir A; Kozlova, Svetlana G; Gabuda, Svyatoslav P

    2014-08-15

    Monolayered titanium disulfide TiS2, a prospective nanoelectronic material, was previously shown to be subject to an exothermic solid-state D3h -D3d reaction that proceeds via a newly discovered transition state. Here, we study the reaction in detail using topological methods of quantum chemistry (quantum theory of atoms in molecules and electron localization function analysis) and show how electron density and chemical bonding between the atoms change in the course of the reaction. The reaction is shown to undergo a series of topological catastrophes, associated with elementary chemical events such as break and formation of bonds (including the unexpected formation of S-S bonding between sulfur layers), and rearrangement of electron density of outer valence and core shells.

  6. Intermediates in the transformation of phosphonates to phosphate by bacteria.

    Science.gov (United States)

    Kamat, Siddhesh S; Williams, Howard J; Raushel, Frank M

    2011-11-16

    Phosphorus is an essential element for all known forms of life. In living systems, phosphorus is an integral component of nucleic acids, carbohydrates and phospholipids, where it is incorporated as a derivative of phosphate. However, most Gram-negative bacteria have the capability to use phosphonates as a nutritional source of phosphorus under conditions of phosphate starvation. In these organisms, methylphosphonate is converted to phosphate and methane. In a formal sense, this transformation is a hydrolytic cleavage of a carbon-phosphorus (C-P) bond, but a general enzymatic mechanism for the activation and conversion of alkylphosphonates to phosphate and an alkane has not been elucidated despite much effort for more than two decades. The actual mechanism for C-P bond cleavage is likely to be a radical-based transformation. In Escherichia coli, the catalytic machinery for the C-P lyase reaction has been localized to the phn gene cluster. This operon consists of the 14 genes phnC, phnD, …, phnP. Genetic and biochemical experiments have demonstrated that the genes phnG, phnH, …, phnM encode proteins that are essential for the conversion of phosphonates to phosphate and that the proteins encoded by the other genes in the operon have auxiliary functions. There are no functional annotations for any of the seven proteins considered essential for C-P bond cleavage. Here we show that methylphosphonate reacts with MgATP to form α-D-ribose-1-methylphosphonate-5-triphosphate (RPnTP) and adenine. The triphosphate moiety of RPnTP is hydrolysed to pyrophosphate and α-D-ribose-1-methylphosphonate-5-phosphate (PRPn). The C-P bond of PRPn is subsequently cleaved in a radical-based reaction producing α-D-ribose-1,2-cyclic-phosphate-5-phosphate and methane in the presence of S-adenosyl-L-methionine. Substantial quantities of phosphonates are produced worldwide for industrial processes, detergents, herbicides and pharmaceuticals. Our elucidation of the chemical steps for the

  7. Survival of bonded lingual retainers with chemical or photo polymerization over a 2-year period: a single-center, randomized controlled clinical trial

    NARCIS (Netherlands)

    Pandis, N.; Fleming, P.S.; Kloukos, D.; Polychronopoulou, A.; Katsaros, C.; Eliades, T.

    2013-01-01

    INTRODUCTION: The objective of this trial was to compare the survival rates of mandibular lingual retainers bonded with either chemically cured or light-cured adhesive after orthodontic treatment. METHODS: Patients having undergone orthodontic treatment at a private orthodontic office were randomly

  8. The Effects of Reasoning, Use of Models, Sex Type, and Their Interactions on Posttest Achievement in Chemical Bonding after Constant Instruction.

    Science.gov (United States)

    Staver, John R.; Halsted, Douglas A.

    1985-01-01

    Determined the effects of reasoning, use of models during testing, and sex type on posttest achievement in chemical bonding under controlled instruction. Indicates that chemistry students' (N=84) reasoning capabilities influenced performance; other variables were not significant. Other conclusions are noted and discussed. (DH)

  9. Sodium Phosphate

    Science.gov (United States)

    Sodium phosphate is used in adults 18 years of age or older to empty the colon (large intestine, bowel) ... view of the walls of the colon. Sodium phosphate is in a class of medications called saline ...

  10. Phosphate salts

    Science.gov (United States)

    ... levels that are too high, and for preventing kidney stones. They are also taken for treating osteomalacia (often ... But intravenous phosphate salts should not be used. Kidney stones (nephrolithiasis). Taking potassium phosphate by mouth might help ...

  11. Effect of conditioning methods on the microtensile bond strength of phosphate monomer-based cement on zirconia ceramic in dry and aged conditions.

    Science.gov (United States)

    Amaral, Regina; Ozcan, Mutlu; Valandro, Luiz Felipe; Balducci, Ivan; Bottino, Marco Antonio

    2008-04-01

    The objective of this study was to evaluate the durability of bond strength between a resin cement and aluminous ceramic submitted to various surface conditioning methods. Twenty-four blocks (5 x 5 x 4 mm(3)) of a glass-infiltrated zirconia-alumina ceramic (In-Ceram Zirconia Classic) were randomly divided into three surface treatment groups: ST1-Air-abrasion with 110-mum Al2O3 particles + silanization; ST2-Laboratory tribochemical silica coating method (110-microm Al2O3, 110-microm silica) (Rocatec) + silanization; ST3-Chairside tribochemical silica coating method (30-microm SiO(x)) (CoJet) + silanization. Each treated ceramic block was placed in its silicone mold with the treated surface exposed. The resin cement (Panavia F) was prepared and injected into the mold over the treated surface. Specimens were sectioned to achieve nontrimmed bar specimens (14 sp/block) that were randomly divided into two conditions: (a) Dry-microtensile test after sectioning; (b) Thermocycling (TC)-(6,000x, 5-55 degrees C) and water storage (150 days). Thus, six experimental groups were obtained (n = 50): Gr1-ST1 + dry; Gr2-ST1 + TC(;) Gr3-ST2 + dry; Gr4-ST2 + TC; Gr5-ST3 + dry; Gr6-ST3 + TC. After microtensile testing, the failure types were noted. ST2 (25.1 +/- 11) and ST3 (24.1 +/- 7.4) presented statistically higher bond strength (MPa) than that of ST1 (17.5 +/- 8) regardless of aging conditions (p silanization showed durable bond strength. After aging, air-abrasion with 110-microm Al(2)O(3) + silanization showed the largest decrease indicating that aging is fundamental for bond strength testing for acid-resistant zirconia ceramics in order to estimate their long-term performance in the mouth.

  12. 40 CFR 721.5995 - Polyalkyl phosphate.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Polyalkyl phosphate. 721.5995 Section... Substances § 721.5995 Polyalkyl phosphate. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a polyalkyl phosphate (PMN P-95-1772)...

  13. Calcium phosphate thin films synthesized by pulsed laser deposition: Physico-chemical characterization and in vitro cell response

    Energy Technology Data Exchange (ETDEWEB)

    Mihailescu, I.N. [National Institute for Lasers, Plasma and Radiation Physics, 77125 Bucharest-Magurele (Romania)]. E-mail: mihailes@ifin.nipne.ro; Torricelli, P. [Servizio di Chirurgia Sperimentale-Istituto di Ricerca Codivilla PuttiIOR, Bologna (Italy); Bigi, A. [Department of Chemistry ' G. Ciamician' , University of Bologna, 40126 Bologna (Italy); Mayer, I. [Department of Inorganic and Analytical Chemistry, Hebrew University of Jerusalem, 91904 Jerusalem (Israel); Iliescu, M. [Institute of Physics and Chemistry of Materials, 67037 Strasbourg (France); Werckmann, J. [Institute of Physics and Chemistry of Materials, 67037 Strasbourg (France); Socol, G. [National Institute for Lasers, Plasma and Radiation Physics, 77125 Bucharest-Magurele (Romania); Miroiu, F. [National Institute for Lasers, Plasma and Radiation Physics, 77125 Bucharest-Magurele (Romania); Cuisinier, F. [Institut National de la Sante et de la Recherche Medicale, 67085 Strasbourg (France); Elkaim, R. [Institut National de la Sante et de la Recherche Medicale, 67085 Strasbourg (France); Hildebrand, G. [IBA e.V., Department of Biomaterials, Rosenhof, D-37308 Heilbad Heiligenstadt (Germany)

    2005-07-30

    We review the progress made by us using pulsed laser deposition (PLD) of two bioactive calcium phosphates: octacalcium phosphate (OCP) and Mn doped carbonated hydroxyapatite (Mn-CHA). Coatings of these materials well suited for biomimetic medical prostheses and pivots were synthesized on titanium substrates with a pulsed KrF* UV laser source. The best deposition conditions for Mn-CHA thin films were 13 Pa O{sub 2}, 400 deg. C with post heat treatment of 6 h in air enriched with water vapours. The coatings are stoichiometric and crystalline. For OCP, deposition at 150 deg. C in 50 Pa water vapor atmosphere, post treated by 6 h annealing in hot flux of water vapours, resulted in stoichiometric, but poorly-crystallized films. Degradation tests show different behavior for the OCP and Mn-CHA coatings. In vitro cell growth shows excellent adherence and biocompatibility of osteoblasts and fibroblasts in both OCP and Mn-CHA coatings. Human osteoblasts display normal proliferation and viability, and good differentiation behaviour.

  14. Simple fabrication of hydrophilic nanochannels using the chemical bonding between activated ultrathin PDMS layer and cover glass by oxygen plasma.

    Science.gov (United States)

    Kim, So Hyun; Cui, Yidan; Lee, Min Jung; Nam, Seong-Won; Oh, Doori; Kang, Seong Ho; Kim, Youn Sang; Park, Sungsu

    2011-01-21

    This study describes a simple and low cost method for fabricating enclosed transparent hydrophilic nanochannels by coating low-viscosity PDMS (monoglycidyl ether-terminated polydimethylsiloxane) as an adhesion layer onto the surface of the nanotrenches that are molded with a urethane-based UV-curable polymer, Norland Optical Adhesive (NOA 63). In detail, the nanotrenches made of NOA 63 were replicated from a Si master mold and coated with 6 nm thick layer of PDMS. These nanotrenches underwent an oxygen plasma treatment and finally were bound to a cover glass by chemical bonding between silanol and hydroxyl groups. Hydrophobic recovery that is observed in the bulk PDMS was not observed in the thin film of PDMS on the mold and the PDMS-coated nanochannel maintained its surface hydrophilicity for at least one month. The potentials of the nanochannels for bioapplications were demonstrated by stretching λ-DNA (48,502 bp) in the channels. Therefore, this fabrication approach provides a practical solution for the simple fabrication of the nanochannels for bioapplications.

  15. Evaluation of the flocculation performance of carboxymethyl chitosan-graft-polyacrylamide, a novel amphoteric chemically bonded composite flocculant.

    Science.gov (United States)

    Yang, Zhen; Yuan, Bo; Huang, Xin; Zhou, Junyu; Cai, Jun; Yang, Hu; Li, Aimin; Cheng, Rongshi

    2012-01-01

    In the present work, a novel amphoteric chemically bonded composite flocculant (carboxymethyl chitosan-graft-polyacrylamide, denoted as CMC-g-PAM) was successfully prepared and used to flocculate the kaolin suspension. The flocculation performance of CMC-g-PAM in acidic, neutral, and alkaline conditions was systematically evaluated by light scattering in combination with fractal theory, as well as by traditional turbidity and zeta potential measurements. Based on the experimental facts from in situ size and fractal dimension measurements, different flocculation mechanisms play key roles at various pH levels, resulting in substantially varied flocculation kinetic processes under three pH conditions. In acidic condition, patching was the main mechanism involved in the opposite zeta potential between CMC-g-PAM and the kaolin suspension. A flat configuration was favored when the polymeric flocculant was adsorbed onto the particle surface, leading to a slower initial floc growth rate but larger and denser flocs. Bridging was the dominant mechanism in neutral and alkaline conditions. A faster initial rate of bridging resulted in smaller and more open floc structures. A rearrangement process in neutral pH subsequently led to more compact flocs, whereas no restructuration of flocs occurred in alkaline conditions because of the electrostatic repulsion of the same negative charges on the flocculant and particles.

  16. Effects of lithium doping on microstructure, electrical properties, and chemical bonds of sol-gel derived NKN thin films

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Chun-Cheng [Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Department of Mathematic and Physical Sciences, R.O.C. Air Force Academy, Kaohsiung 820, Taiwan (China); Chen, Chan-Ching; Weng, Chung-Ming [Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Chu, Sheng-Yuan, E-mail: chusy@mail.ncku.edu.tw [Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Hong, Cheng-Shong [Department of Electronic Engineering, National Kaohsiung Normal University, Kaohsiung 802, Taiwan (China); Tsai, Cheng-Che [Department of Digital Game and Animation Design, Tung-Fang Design University, Kaohsiung 829, Taiwan (China)

    2015-02-28

    Highly (100/110) oriented lead-free Li{sub x}(Na{sub 0.5}K{sub 0.5}){sub 1−x}NbO{sub 3} (LNKN, x = 0, 0.02, 0.04, and 0.06) thin films are fabricated on Pt/Ti/SiO{sub 2}/Si substrates via a sol-gel processing method. The lithium (Li) dopants modify the microstructure and chemical bonds of the LNKN films, and therefore improve their electrical properties. The optimal values of the remnant polarization (P{sub r} = 14.3 μC/cm{sup 2}), piezoelectric coefficient (d{sub 33} = 48.1 pm/V), and leakage current (<10{sup −5} A/cm{sup 2}) are obtained for a lithium addition of x = 0.04 (i.e., 4 at. %). The observation results suggest that the superior electrical properties are the result of an improved crystallization, a larger grain size, and a smoother surface morphology. It is shown that the ion transport mechanism is dominated by an Ohmic behavior under low electric fields and the Poole-Frenkel emission effect under high electric fields.

  17. Laser-assisted one-pot fabrication of calcium phosphate-based submicrospheres with internally crystallized magnetite nanoparticles through chemical precipitation.

    Science.gov (United States)

    Nakamura, Maki; Oyane, Ayako; Sakamaki, Ikuko; Ishikawa, Yoshie; Shimizu, Yoshiki; Kawaguchi, Kenji

    2015-04-14

    In this paper, we have further developed our simple (one-pot) and rapid (short irradiation time) laser fabrication process of submicrometer spheres composed of amorphous calcium iron phosphate. In our previous process, laser irradiation was applied to a calcium phosphate (CaP) reaction mixture supplemented with ferric ions (Fe(3+)) as a light-absorbing agent. Because the intention of the present study was to fabricate magnetite-encapsulated CaP-based submicrometer spheres, ferrous ions (Fe(2+)) were used as a light-absorbing agent rather than ferric ions. The ferrous ions served as a light-absorbing agent and facilitated the fabrication of submicrometer and micrometer spheres of amorphous calcium iron phosphate. The sphere formation and growth were better promoted by the use of ferrous ions as compared with the use of ferric ions. The chemical composition of the spheres was controllable through adjustment of the experimental conditions. By the addition of sodium hydroxide to the CaP reaction mixture supplemented with ferrous ions, fabrication of CaP-based magnetic submicrometer spheres was successfully achieved. Numerous magnetite and wüstite nanoparticles were coprecipitated or segregated into the CaP-based spherical amorphous matrix via light-material interaction during the CaP precipitation process. The magnetic properties of the magnetite and wüstite formed in the CaP-based spheres were investigated by magnetization measurements. The present process and the resulting CaP-based spheres are expected to have great potential for biomedical applications.

  18. Structures and chemical bonding of B3O3 (-/0) and B3O3H(-/0): A combined photoelectron spectroscopy and first-principles theory study.

    Science.gov (United States)

    Zhao, Li-Juan; Tian, Wen-Juan; Ou, Ting; Xu, Hong-Guang; Feng, Gang; Xu, Xi-Ling; Zhai, Hua-Jin; Li, Si-Dian; Zheng, Wei-Jun

    2016-03-28

    We present a combined photoelectron spectroscopy and first-principles theory study on the structural and electronic properties and chemical bonding of B3O3 (-/0) and B3O3H(-/0) clusters. The concerted experimental and theoretical data show that the global-minimum structures of B3O3 and B3O3H neutrals are very different from those of their anionic counterparts. The B3O3 (-) anion is characterized to possess a V-shaped OB-B-BO chain with overall C2 v symmetry (1A), in which the central B atom interacts with two equivalent boronyl (B≡O) terminals via B-B single bonds as well as with one O atom via a B=O double bond. The B3O3H(-) anion has a Cs (2A) structure, containing an asymmetric OB-B-OBO zig-zag chain and a terminal H atom interacting with the central B atom. In contrast, the C2 v (1a) global minimum of B3O3 neutral contains a rhombic B2O2 ring with one B atom bonded to a BO terminal and that of neutral B3O3H (2a) is also of C2 v symmetry, which is readily constructed from C2 v (1a) by attaching a H atom to the opposite side of the BO group. The H atom in B3O3H(-/0) (2A and 2a) prefers to interact terminally with a B atom, rather than with O. Chemical bonding analyses reveal a three-center four-electron (3c-4e) π hyperbond in the B3O3H(-) (2A) cluster and a four-center four-electron (4c-4e) π bond (that is, the so-called o-bond) in B3O3 (1a) and B3O3H (2a) neutral clusters.

  19. Effect of zinc phosphate chemical conversion coating on corrosion behaviour of mild steel in alkaline medium: protection of rebars in reinforced concrete

    Directory of Open Access Journals (Sweden)

    Florica Simescu and Hassane Idrissi

    2008-01-01

    Full Text Available We outline the ability of zinc phosphate coatings, obtained by chemical conversion, to protect mild steel rebars against localized corrosion, generated by chloride ions in alkaline media. The corrosion resistance of coated steel, in comparison with uncoated rebars and coated and uncoated steel rebars embedded in mortar, were evaluated by open-circuit potential, potentiodynamic polarization, cronoamperometry and electrochemical impedance spectroscopy. The coated surfaces were characterized by x-ray diffraction and scanning electron microscopy. First, coated mild steel rebars were studied in an alkaline solution with and without chloride simulating a concrete pore solution. The results showed that the slow dissolution of the coating generates hydroxyapatite Ca10(PO46(OH2. After a long immersion, the coating became dense and provided an effective corrosion resistance compared with the mild steel rebar. Secondly, the coated and uncoated steel rebars embedded in mortar and immersed in chloride solution showed no corrosion or deterioration of the coated steel. Corrosion rate is considerably lowered by this phosphate coating.

  20. Effect of zinc phosphate chemical conversion coating on corrosion behaviour of mild steel in alkaline medium: protection of rebars in reinforced concrete.

    Science.gov (United States)

    Simescu, Florica; Idrissi, Hassane

    2008-12-01

    We outline the ability of zinc phosphate coatings, obtained by chemical conversion, to protect mild steel rebars against localized corrosion, generated by chloride ions in alkaline media. The corrosion resistance of coated steel, in comparison with uncoated rebars and coated and uncoated steel rebars embedded in mortar, were evaluated by open-circuit potential, potentiodynamic polarization, cronoamperometry and electrochemical impedance spectroscopy. The coated surfaces were characterized by x-ray diffraction and scanning electron microscopy. First, coated mild steel rebars were studied in an alkaline solution with and without chloride simulating a concrete pore solution. The results showed that the slow dissolution of the coating generates hydroxyapatite Ca10(PO4)6(OH)2. After a long immersion, the coating became dense and provided an effective corrosion resistance compared with the mild steel rebar. Secondly, the coated and uncoated steel rebars embedded in mortar and immersed in chloride solution showed no corrosion or deterioration of the coated steel. Corrosion rate is considerably lowered by this phosphate coating.

  1. Zinc phosphate as versatile material for potential biomedical applications Part II.

    Science.gov (United States)

    Herschke, L; Lieberwirth, I; Wegner, G

    2006-01-01

    Surface chemical reactivity of two modifications of synthetic zinc phosphate tetrahydrate (alpha - and beta -form of Hopeite, alpha -,beta -ZPT) has been studied by selective chemical and e-beam etching in presence of diluted phosphoric acid and ammonia by Scanning Electron Microscopy (SEM) and microelectrophoresis (zeta potential measurements) in correlation with the corresponding bulk properties and crystal size distributions. The subtitle crystallographic differences between alpha -and beta -ZPT originating from a unique hydrogen bonding pattern, induce drastic variations of both surface potential and surface charge. Biogenic Hydroxyapatite (HAP) and one of its metastable precursors, a calcium dihydrogen phosphate dihydrate (DCPD) or Brushite were used to underline this resulting variation of chemical reactivity in zinc phosphates. In-situ monitoring of the transformation of Brushite in Hydroxyapatite is also reported.

  2. Structural and crystal chemical properties of rare-earth double phosphates and rare-earth titanate pyrochlores

    Science.gov (United States)

    Farmer, J. Matt

    Alkali rare-earth double phosphates have been studied for use as long-wavelength scintillators for gamma-ray detection using Si photodiodes. These compounds exhibit layered crystal structures, built from roughly hexagonal atomic layers in the sequence lanthanide, phosphate-alkali, alkali, alkali-phosphate. Details of the crystal symmetry depend on the relative sizes of the rare-earth and alkali metal ions. Single-crystal X-ray diffraction (SXRD) has been used to study these structures at room temperature for K3RE(PO4) 2 (where RE = Lu-Ce, Y, and Sc). The compound K3Lu(PO 4)2 crystallizes with a hexagonal unit cell, space group P-3. The Lu ion is six-coordinated to the oxygen atoms of the phosphate groups. Two lower-temperature phases of K3Lu(PO4) 2 were observed and characterized. The lower-temperature transition results in an increase in coordination of the Lu ion to seven fold. This new structure is isostructural with the room-temperature form of K3Yb(PO 4)2. High-temperature powder neutron diffraction and high-temperature powder XRD have revealed a large thermal expansion anisotropy for K3Lu(PO4)2. The K3RE(PO 4)2 formation enthalpies were determined using high-temperature oxide-melt solution calorimetry. The formation enthalpy from oxides becomes more exothermic with increasing rare-earth radius. Rare-earth titanates, RE2Ti2O7 (where RE = a rare-earth), with the pyrochlore structure are currently being studied for use as potential nuclear, actinide-rich waste forms. Single-crystals were synthesized using a high-temperature flux technique and characterized using single-crystal X-ray diffraction. The cubic lattice parameters display an approximately linear correlation with the RE-site cation radius. The Sm and Eu titanates exhibit a covalency increase between the REO8 and TiO6 polyhedra resulting in a deviation from the increasing linear lattice parameter through the series. Gd2Ti2O7 exhibits the lowest 48f oxygen positional parameter, an effect that can be

  3. Oligomerization reactions of deoxyribonucleotides on montmorillonite clay - The effect of mononucleotide structure, phosphate activation and montmorillonite composition on phosphodiester bond formation

    Science.gov (United States)

    Ferris, James P.; KAMALUDDIN; Ertem, Gozen

    1990-01-01

    The 2(prime)-d-5(prime)-GMP and 2(prime)-d-5(prime)-AMP bind 2 times more strongly to montmorillonite 22A than do 2(prime)-d-5(prime)-CMP and 5(prime)-TMP. The dinucleotide d(pG)2 forms in 9.2 percent yield and the cyclic dinucleotide c(dpG)2 in 5.4 percent yield in the reaction of 2(prime)-d-5(prime)-GMP with EDAC in the presence of montmorillonite 22A. The yield of dimers which contain the phosphodiester bond decreases as the reaction medium is changed from 0.2 M NaCl to a mixture of 0.2 M NaCl and 0.075 M MgCl2. A low yield of d(pA)2 was observed in the condensation reaction of 5(prime)-ImdpA on montmorillonite 22A. The yield of d(pA)2 obtained when EDAC is used as the condensing agent increases with increasing iron content of the Na(+)-montmorillonite used as catalyst. Evidence is presented which shows that the acidity of the Na(+)-montmorillonite is a necessary but not sufficient factor for the montmorillonite catalysis of phosphodiester bond formation.

  4. Novel fluoro-carbon functional monomer for dental bonding.

    Science.gov (United States)

    Yoshihara, K; Yoshida, Y; Hayakawa, S; Nagaoka, N; Kamenoue, S; Okihara, T; Ogawa, T; Nakamura, M; Osaka, A; Van Meerbeek, B

    2014-02-01

    Among several functional monomers, 10-methacryloxydecyl dihydrogen phosphate (10-MDP) bonded most effectively to hydroxyapatite (HAp). However, more hydrolysis-resistant functional monomers are needed to improve bond durability. Here, we investigated the adhesive potential of the novel fluoro-carbon functional monomer 6-methacryloxy-2,2,3,3,4,4,5,5-octafluorohexyl dihydrogen phosphate (MF8P; Kuraray Noritake Dental Inc., Tokyo, Japan) by studying its molecular interaction with powder HAp using solid-state nuclear magnetic resonance ((1)H MAS NMR) and with dentin using x-ray diffraction (XRD) and by characterizing its interface ultrastructure at dentin using transmission electron microscopy (TEM). We further determined the dissolution rate of the MF8P_Ca salt, the hydrophobicity of MF8P, and the bond strength of an experimental MF8P-based adhesive to dentin. NMR confirmed chemical adsorption of MF8P onto HAp. XRD and TEM revealed MF8P_Ca salt formation and nano-layering at dentin. The MF8P_Ca salt was as stable as that of 10-MDP; MF8P was as hydrophobic as 10-MDP; a significantly higher bond strength was recorded for MF8P than for 10-MDP. In conclusion, MF8P chemically bonded to HAp. Despite its shorter size, MF8P possesses characteristics similar to those of 10-MDP, most likely to be associated with the strong chemical bond between fluorine and carbon. Since favorable bond strength to dentin was recorded, MF8P can be considered a good candidate functional monomer for bonding.

  5. Density functional theory investigation of hydrogen bonding effects on the oxygen, nitrogen and hydrogen electric field gradient and chemical shielding tensors of anhydrous chitosan crystalline structure.

    Science.gov (United States)

    Esrafili, Mehdi D; Elmi, Fatemeh; Hadipour, Nasser L

    2007-02-08

    A systematic computational investigation was carried out to characterize the 17O, 14N and 2H electric field gradient, EFG, as well as 17O, 15N, 13C and 1H chemical shielding tensors in the anhydrous chitosan crystalline structure. To include the hydrogen-bonding effects in the calculations, the most probable interacting molecules with the target molecule in the crystalline phase were considered through a hexameric cluster. The computations were performed with the B3LYP method and 6-311++G(d,p) and 6-31++G(d,p) standard basis sets using the Gaussian 98 suite of programs. Calculated EFG and chemical shielding tensors were used to evaluate the 17O, 14N and 2H nuclear quadrupole resonance, NQR, and 17O, 15N, 13C and 1H nuclear magnetic resonance, NMR, parameters in the hexameric cluster, which are in good agreement with the available experimental data. The difference between the calculated NQR and NMR parameters of the monomer and hexamer cluster shows how much hydrogen bonding interactions affect the EFG and chemical shielding tensors of each nucleus. These results indicate that both O(3)-H(33)...O(5-3) and N-H(22)...O(6-4) hydrogen bonding have a major influence on NQR and NMR parameters. Also, the quantum chemical calculations indicate that the intra- and intermolecular hydrogen bonding interactions play an essential role in determining the relative orientation of EFG and chemical shielding principal components in the molecular frame axes.

  6. The electronic nature of the 1,4-β-glycosidic bond and its chemical environment: DFT insights into cellulose chemistry.

    Science.gov (United States)

    Loerbroks, Claudia; Rinaldi, Roberto; Thiel, Walter

    2013-11-25

    The molecular understanding of the chemistry of 1,4-β-glucans is essential for designing new approaches to the conversion of cellulose into platform chemicals and biofuels. In this endeavor, much attention has been paid to the role of hydrogen bonding occurring in the cellulose structure. So far, however, there has been little discussion about the implications of the electronic nature of the 1,4-β-glycosidic bond and its chemical environment for the activation of 1,4-β-glucans toward acid-catalyzed hydrolysis. This report sheds light on these central issues and addresses their influence on the acid hydrolysis of cellobiose and, by analogy, cellulose. The electronic structure of cellobiose was explored by DFT at the BB1 K/6-31++G(d,p) level. Natural bond orbital (NBO) analysis was performed to grasp the key bonding concepts. Conformations, protonation sites, and hydrolysis mechanisms were examined. The results for cellobiose indicate that cellulose is protected against hydrolysis not only by its supramolecular structure, as currently accepted, but also by its electronic structure, in which the anomeric effect plays a key role.

  7. Solvent-free thermoplastic-poly(dimethylsiloxane) bonding mediated by UV irradiation followed by gas-phase chemical deposition of an adhesion linker

    Science.gov (United States)

    Ahn, S. Y.; Lee, N. Y.

    2015-07-01

    Here, we introduce a solvent-free strategy for bonding various thermoplastic substrates with poly(dimethylsiloxane) (PDMS) using ultraviolet (UV) irradiation followed by the gas-phase chemical deposition of aminosilane on the UV-irradiated thermoplastic substrates. The thermoplastic substrates were first irradiated with UV for surface hydrophilic treatment and were then grafted with vacuum-evaporated aminosilane, where the alkoxysilane side reacted with the oxidized surface of the thermoplastic substrate. Next, the amine-terminated thermoplastic substrates were treated with corona discharge to oxidize the surface and were bonded with PDMS, which was also oxidized via corona discharge. The two substrates were then hermetically sealed and pressed under atmospheric pressure for 30 min at 60 °C. This process enabled the formation of a robust siloxane bond (Si-O-Si) between the thermoplastic substrate and PDMS under relatively mild conditions using an inexpensive and commercially available UV lamp and Tesla coil. Various thermoplastic substrates were examined for bonding with PDMS, including poly(methylmethacrylate) (PMMA), polycarbonate (PC), poly(ethyleneterephthalate) (PET) and polystyrene (PS). Surface characterizations were performed by measuring the contact angle and performing x-ray photoelectron spectroscopy analysis, and the bond strength was analyzed by conducting various mechanical force measurements such as pull, delamination, leak and burst tests. The average bond strengths for the PMMA-PDMS, PC-PDMS, PET-PDMS and PS-PDMS assemblies were measured at 823.6, 379.3, 291.2 and 229.0 kPa, respectively, confirming the highly reliable performance of the introduced bonding strategy.

  8. Chemical bond properties and Mossbauer spectroscopy in (La1-xMx)2CuO4 (M=Ba, Sr)

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    By using the average band-gap model, the chemical bond properties of (La1-x Mx)2CuO4(M=Ba, Sr) were calculated . The calculated covalencies for Cu(O and La(O bond in the compounds are 0.3 and 0.03 respectively. M?ssbauer isomer shifts of 57Fe doped in La2CuO4 and 119Sn doped in La2CuO4 were calculated by using the chemical surrounding factor defined by covalency and electronic polarizability. Four valence state tin and three valence iron sites were identified in 57Fe and 119Sn doped La2CuO4.

  9. Tensile bond strength of silicone-based soft denture liner to two chemically different denture base resins after various surface treatments.

    Science.gov (United States)

    Akin, Hakan; Tugut, Faik; Guney, Umit; Kirmali, Omer; Akar, Turker

    2013-01-01

    This study evaluated the effect of various surface treatments on the tensile bond strength of a silicone-based soft denture liner to two chemically different denture base resins, heat-cured polymethyl methacrylate (PMMA), and light-activated urethane dimethacrylate or Eclipse denture base resin. PMMA test specimens were fabricated and relined with a silicone-based soft denture liner (group AC). Eclipse test specimens were prepared according to the manufacturer's recommendation. Before they were relined with a silicone-based soft denture liner, each received one of three surface treatments: untreated (control, group EC), Eclipse bonding agent applied (group EB), and laser-irradiated (group EL). Tensile bond strength tests (crosshead speed = 5 mm/min) were performed for all specimens, and the results were analyzed using the analysis of variance followed by Tukey's test (p = 0.05). Eclipse denture base and PMMA resins presented similar bond strengths to the silicone-based soft denture liner. The highest mean force was observed in group EL specimens, and the tensile bond strengths in group EL were significantly different (p < 0.05) from those in the other groups.

  10. Kinetic and Thermodynamic Studies on the Phosphate Adsorption Removal by Dolomite Mineral

    Directory of Open Access Journals (Sweden)

    Xiaoli Yuan

    2015-01-01

    Full Text Available The efficiency of dolomite to remove phosphate from aqueous solutions was investigated. The experimental results showed that the removal of phosphate by dolomite was rapid (the removal rate over 95% in 60 min when the initial phosphate concentration is at the range of 10–50 mg/L. Several kinetic models including intraparticle diffusion model, pseudo-first-order model, Elovich model, and pseudo-second-order model were employed to evaluate the kinetics data of phosphate adsorption onto dolomite and pseudo-second-order model was recommended to describe the adsorption kinetics characteristics. Further analysis of the adsorption kinetics indicated that the phosphate removal process was mainly controlled by chemical bonding or chemisorption. Moreover, both Freundlich and Langmuir adsorption isotherms were used to evaluate the experimental data. The results indicated that Langmuir isotherm was more suitable to describe the adsorption characteristics of dolomite. Maximum adsorption capacity of phosphate by dolomite was found to be 4.76 mg phosphorous/g dolomite. Thermodynamic studies showed that phosphate adsorption was exothermic. The study implies that dolomite is an excellent low cost material for phosphate removal in wastewater treatment process.

  11. Intermolecular CH···O/N H-bonds in the biologically important pairs of natural nucleobases: a thorough quantum-chemical study.

    Science.gov (United States)

    Brovarets', Ol'ha O; Yurenko, Yevgen P; Hovorun, Dmytro M

    2014-01-01

    This study aims to cast light on the physico-chemical nature and energetic of the non-conventional CH···O/N H-bonds in the biologically important natural nucleobase pairs using a comprehensive quantum-chemical approach. As a whole, the 36 biologically important pairs, involving canonical and rare tautomers of nucleobases, were studied by means of all available up-to-date state-of-the-art quantum-chemical techniques along with quantum theory "Atoms in molecules" (QTAIM), Natural Bond Orbital (NBO) analysis, Grunenberg's compliance constants theory, geometrical and vibrational analyses to identify the CH···O/N interactions, reveal their physico-chemical nature and estimate their strengths as well as contribution to the overall base-pairs stability. It was shown that all the 38 CH···O/N contacts (25 CH···O and 13 CH···N H-bonds) completely satisfy all classical geometrical, electron-topological, in particular Bader's and "two-molecule" Koch and Popelier's, and vibrational criteria of H-bonding. The positive values of Grunenberg's compliance constants prove that the CH···O/N contacts in nucleobase pairs are stabilizing interactions unlike electrostatic repulsion and anti-H-bonds. NBO analysis indicates the electron density transfer from the lone electron pair of the acceptor atom (O/N) to the antibonding orbital corresponding to the donor group σ(∗)(CH). Moreover, significant increase in the frequency of the out-of-plane deformation modes γ (CH) under the formation of the CH···O (by 17.2÷81.3/10.8÷84.7 cm(-1)) and CH···N (by 32.7÷85.9/9.0÷77.9 cm(-1)) H-bonds at the density functional theory (DFT)/second-order Møller-Plesset (MP2) levels of theory, respectively, and concomitant changes of their intensities can be considered as reliable indicators of H-bonding. The strengths of the CH···O/N interactions, evaluated by means of Espinosa-Molins-Lecomte formula, lie within the range 0.45÷3.89/0.62÷4.10 kcal/mol for the CH

  12. Unique chemical properties of metal-carbon bonds in metal-carboranyl and metal-carboryne complexes

    Institute of Scientific and Technical Information of China (English)

    QIU ZaoZao; XIE ZuoWei

    2009-01-01

    The metal-carbon bonds in metal-carboranyl and metal-carboryne complexes behave very differently from those in classical organometallic complexes. The unique electronic and steric properties of icosahedral carboranyl moiety make the M-C bond in metal-carboranyl complexes inert toward unsaturated molecules, and on the other hand, the sterically demanding carborane cage can induce unexpected C-C coupling reactions. The M-C bonds in metal-carboryne complexes are, however, active toward various kinds of unsaturated molecules and the reactivity patterns are dependent upon the electronic configurations of the metal ions. This account provides an overview of our recent work in this area.

  13. Unique chemical properties of metal-carbon bonds in metal-carboranyl and metal-carboryne complexes

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The metal-carbon bonds in metal-carboranyl and metal-carboryne complexes behave very differently from those in classical organometallic complexes. The unique electronic and steric properties of ico-sahedral carboranyl moiety make the M-C bond in metal-carboranyl complexes inert toward unsaturated molecules, and on the other hand, the sterically demanding carborane cage can induce unexpected C-C coupling reactions. The M-C bonds in metal-carboryne complexes are, however, active toward various kinds of unsaturated molecules and the reactivity patterns are dependent upon the electronic configurations of the metal ions. This account provides an overview of our recent work in this area.

  14. Atomic volume, atomic distances and chemical bonding in solid metallic elements; Atomvolumen, Atomabstaende und chemische Bindung in festen metallischen Elementen

    Energy Technology Data Exchange (ETDEWEB)

    Troemel, M.; Huebner, S. [Frankfurt Univ. (Germany). Inst. fuer Anorganische Chemie

    2001-05-01

    Relationships between bond lengths and bond numbers and also between atomic volumes and valencies are derived and parameters for their calculation are given for the s-block, p-block, and d-block metals. From the atomic volumes under pressure, the valencies of three solid lanthanoids have been confirmed or redetermined: La 3; Ce 2, 3, and 4; Yb 2 and 3. (orig.)

  15. Phosphate ceramic solidification and stabilization of cesium-containing crystalline silicotitanate resins.

    Energy Technology Data Exchange (ETDEWEB)

    Langton, C. A.

    1999-05-11

    This paper reports on the fabrication and testing of magnesium potassium phosphate (MKP)-bonded cesium-loaded crystalline silicotitanate (CST) resins. Typical waste loading of CST resins in the final waste forms was 50 wt.%. Physical and chemical characterization of the MKP materials has shown them to be physically, chemically, and mineralogically stable. Long-term durability studies (using the AN 16.1 standard test) showed a leachability index of {approx}18 for cesium in the phosphate matrix when exposed to deionized water under ambient and elevated temperatures. Leaching of cesium was somewhat higher than in glass waste forms as per PCT and MCC-1 tests. MKP-based final waste forms showed no significant weight changes after exposure to aqueous media for {approx}90 days, indicating the highly insoluble nature of the phosphate matrix. In addition, durability of the CST-MKP waste forms was further established by freeze-thaw cycling tests.

  16. Evaluation of Questions in General Chemistry Textbooks According to the Form of the Questions and the Question-Answer Relationship (QAR): The Case of Intra-and Intermolecular Chemical Bonding

    Science.gov (United States)

    Pappa, Eleni T.; Tsaparlis, Georgios

    2011-01-01

    One way of checking to what extent instructional textbooks achieve their aim is to evaluate the questions they contain. In this work, we analyze the questions that are included in the chapters on chemical bonding of ten general chemistry textbooks. We study separately the questions on intra- and on intermolecular bonding, with the former…

  17. Electronic structure, chemical bonding and elastic properties of the first thorium-containing nitride perovskite TaThN{sub 3}

    Energy Technology Data Exchange (ETDEWEB)

    Bannikov, V.V.; Shein, I.R.; Ivanovskii, A.L. [Institute of Solid State Chemistry of the Ural Division of the Russian Academy of Sciences, GSP-145, 620041 Ekaterinburg (Russian Federation)

    2007-05-15

    The full-potential linearized augmented plane wave method with the generalized gradient approximation for the exchange and correlation potential (LAPW-GGA) is used to understand the electronic and elastic properties of the first thorium-containing nitride perovskite TaThN{sub 3}. Total and partial density of states, charge distributions as well as the elastic constants, bulk modulus, compressibility, shear modulus, Young modulus and Poisson ratio are obtained for the first time and analyzed in comparison with cubic ThN. The chemical bonding in TaThN{sub 3} is a combination of ionic Th-N and of mixed covalent-ionic Ta-N bonds. The cubic TaThN{sub 3} is semiconducting with the direct gap at about 0.65 eV. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  18. Chemical bonding structural analysis of nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous carbon composite films prepared by coaxial arc plasma deposition

    Science.gov (United States)

    Gima, Hiroki; Zkria, Abdelrahman; Katamune, Yūki; Ohtani, Ryota; Koizumi, Satoshi; Yoshitake, Tsuyoshi

    2017-01-01

    Nitrogen-doped ultra-nanocrystalline diamond/hydrogenated amorphous carbon composite films prepared in hydrogen and nitrogen mixed-gas atmospheres by coaxial arc plasma deposition with graphite targets were studied electrically and chemical-bonding-structurally. The electrical conductivity was increased by nitrogen doping, accompanied by the production of n-type conduction. From X-ray photoemission, near-edge X-ray absorption fine-structure, hydrogen forward-scattering, and Fourier transform infrared spectral results, it is expected that hydrogen atoms that terminate diamond grain boundaries will be partially replaced by nitrogen atoms and, consequently, π C–N and C=N bonds that easily generate free electrons will be formed at grain boundaries.

  19. Effects of silica addition on the chemical, mechanical and biological properties of a new α-Tricalcium Phosphate/Tricalcium Silicate Cement

    Directory of Open Access Journals (Sweden)

    Loreley Morejón-Alonso

    2011-12-01

    Full Text Available The addition of tricalcium silicate (C3S to apatite cements results in an increase of bioactivity and improvement in the mechanical properties. However, adding large amounts raises the local pH at early stages, which retards the precipitation of hydroxyapatite and produces a loss of mechanical strength. The introduction of Pozzolanic materials in cement pastes could be an effective way to reduces basicity and enhance their mechanical resistance; thus, the effect of adding silica on the chemical, mechanical and biological properties of α-tricalcium phosphate/C3S cement was studied. Adding silica produces a reduction in the early pH and a decrease in setting times; nevertheless, the presence of more calcium silicate hydrate (C-S-H delays the growth of hydroxyapatite crystals and consequently, reduces early compressive strength. The new formulations show a good bioactivity, but higher cytotoxicity than traditional cements and additions higher than 2.5% of SiO2 cause a lack of mechanical strength and an elevated degradability.

  20. Quantum chemical study on influence of intermolecular hydrogen bonding on the geometry, the atomic charges and the vibrational dynamics of 2,6-dichlorobenzonitrile.

    Science.gov (United States)

    Agarwal, Parag; Bee, Saba; Gupta, Archana; Tandon, Poonam; Rastogi, V K; Mishra, Soni; Rawat, Poonam

    2014-01-01

    FT-IR (4000-400 cm(-1)) and FT-Raman (4000-200 cm(-1)) spectral measurements on solid 2,6-dichlorobenzonitrile (2,6-DCBN) have been done. The molecular geometry, harmonic vibrational frequencies and bonding features in the ground state have been calculated by density functional theory at the B3LYP/6-311++G (d,p) level. A comparison between the calculated and the experimental results covering the molecular structure has been made. The assignments of the fundamental vibrational modes have been done on the basis of the potential energy distribution (PED). To investigate the influence of intermolecular hydrogen bonding on the geometry, the charge distribution and the vibrational spectrum of 2,6-DCBN; calculations have been done for the monomer as well as the tetramer. The intermolecular interaction energies corrected for basis set superposition error (BSSE) have been calculated using counterpoise method. Based on these results, the correlations between the vibrational modes and the structure of the tetramer have been discussed. Molecular electrostatic potential (MEP) contour map has been plotted in order to predict how different geometries could interact. The Natural Bond Orbital (NBO) analysis has been done for the chemical interpretation of hyperconjugative interactions and electron density transfer between occupied (bonding or lone pair) orbitals to unoccupied (antibonding or Rydberg) orbitals. UV spectrum was measured in methanol solution. The energies and oscillator strengths were calculated by Time Dependent Density Functional Theory (TD-DFT) and matched to the experimental findings. TD-DFT method has also been used for theoretically studying the hydrogen bonding dynamics by monitoring the spectral shifts of some characteristic vibrational modes involved in the formation of hydrogen bonds in the ground and the first excited state. The (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule were calculated by the Gauge independent atomic orbital

  1. A comparative effect of various surface chemical treatments on the resin composite-composite repair bond strength

    Directory of Open Access Journals (Sweden)

    Shaloo Gupta

    2015-01-01

    Full Text Available Aim: The aim of this in vitro study was an attempt to investigate the effect of different surface treatments on the bond strength between pre-existing composite and repair composite resin. Materials and Methods: Forty acrylic blocks were prepared in a cuboidal mould. In each block, a well of 5 mm diameter and 5 mm depth was prepared to retain the composite resin (Filtek™ Z350, 3M/ESPE. Aging of the composite discs was achieved by storing them in water at 37°C for 1 week, and after that were divided into 5 groups (n = 8 according to surface treatment: Group I- 37% phosphoric acid, Group II-10% hydrofluoric acid, Group III-30% citric acid, Group IV-7% maleic acid and Group V- Adhesive (no etchant. The etched surfaces were rinsed and dried followed by application of bonding agent (Adper™ Single Bond 2. 3M/ESPE. The repair composite was placed on aged composite, light-cured for 40 seconds and stored in water at 37°C for 1 week. Shear bond strength between the aged and the new composite resin was determined with a universal testing machine (crosshead speed of 0.5 mm/min. Statistical Analysis: The compressive shear strengths were compared for differences using ANOVA test followed by Tamhane′s T2 post hoc analysis. Results: The surface treatment with 10% hydrofluoric acid showed the maximum bond strength followed by 30% citric acid, 7% maleic acid and 37% phosphoric acid in decreasing order. Conclusion: The use of 10% hydrofluoric acid can be a good alternative for surface treatment in repair of composite resin restoration as compared to commonly used 37% orthophosphoric acid.

  2. Nitrilotris(methylenephosphonato)potassium K[μ6-NH(CH2PO3)3H4]: Synthesis, structure, and the nature of the K-O chemical bond

    Science.gov (United States)

    Somov, N. V.; Chausov, F. F.; Zakirova, R. M.

    2016-07-01

    The crystal structure of nitrilotris(methylenephosphonato)potassium K[μ6-NH(CH2PO3)3H4]—a three-dimensional coordination polymer—was determined. The potassium atom is coordinated by seven oxygen atoms belonging to the six nearest ligand molecules, resulting in distorted monocapped octahedral coordination geometry. The complex contains the four-membered chelate ring K-O-P-O. The K-O chemical bond is predominantly ionic. Meanwhile, the bonds of the potassium atom with some oxygen atoms have a noticeable covalent component. In addition to coordination bonds, the molecules in the crystal packing are linked by hydrogen bonds.

  3. Chemical insight from density functional modeling of molecular adsorption: Tracking the bonding and diffusion of anthracene derivatives on Cu(111) with molecular orbitals

    Science.gov (United States)

    Wyrick, Jonathan; Einstein, T. L.; Bartels, Ludwig

    2015-03-01

    We present a method of analyzing the results of density functional modeling of molecular adsorption in terms of an analogue of molecular orbitals. This approach permits intuitive chemical insight into the adsorption process. Applied to a set of anthracene derivates (anthracene, 9,10-anthraquinone, 9,10-dithioanthracene, and 9,10-diselenonanthracene), we follow the electronic states of the molecules that are involved in the bonding process and correlate them to both the molecular adsorption geometry and the species' diffusive behavior. We additionally provide computational code to easily repeat this analysis on any system.

  4. Chemical insight from density functional modeling of molecular adsorption: Tracking the bonding and diffusion of anthracene derivatives on Cu(111) with molecular orbitals

    Energy Technology Data Exchange (ETDEWEB)

    Wyrick, Jonathan; Bartels, Ludwig, E-mail: ludwig.bartels@ucr.edu [Pierce Hall, University of California-Riverside, Riverside, California 92521 (United States); Einstein, T. L. [Department of Physics and Condensed Matter Theory Center, University of Maryland, College Park, Maryland 20742-4111 (United States)

    2015-03-14

    We present a method of analyzing the results of density functional modeling of molecular adsorption in terms of an analogue of molecular orbitals. This approach permits intuitive chemical insight into the adsorption process. Applied to a set of anthracene derivates (anthracene, 9,10-anthraquinone, 9,10-dithioanthracene, and 9,10-diselenonanthracene), we follow the electronic states of the molecules that are involved in the bonding process and correlate them to both the molecular adsorption geometry and the species’ diffusive behavior. We additionally provide computational code to easily repeat this analysis on any system.

  5. Prevalence of Bimolecular Routes in the Activation of Diatomic Molecules with Strong Chemical Bonds (O2, NO, CO, N2) on Catalytic Surfaces.

    Science.gov (United States)

    Hibbitts, David; Iglesia, Enrique

    2015-05-19

    Dissociation of the strong bonds in O2, NO, CO, and N2 often involves large activation barriers on low-index planes of metal particles used as catalysts. These kinetic hurdles reflect the noble nature of some metals (O2 activation on Au), the high coverages of co-reactants (O2 activation during CO oxidation on Pt), or the strength of the chemical bonds (NO on Pt, CO and N2 on Ru). High barriers for direct dissociations from density functional theory (DFT) have led to a consensus that "defects", consisting of low-coordination exposed atoms, are required to cleave such bonds, as calculated by theory and experiments for model surfaces at low coverages. Such sites, however, bind intermediates strongly, rendering them unreactive at the high coverages prevalent during catalysis. Such site requirements are also at odds with turnover rates that often depend weakly on cluster size or are actually higher on larger clusters, even though defects, such as corners and edges, are most abundant on small clusters. This Account illustrates how these apparent inconsistencies are resolved through activations of strong bonds assisted by co-adsorbates on crowded low-index surfaces. Catalytic oxidations occur on Au clusters at low temperatures in spite of large activation barriers for O2 dissociation on Au(111) surfaces, leading to proposals that O2 activation requires low-coordination Au atoms or Au-support interfaces. When H2O is present, however, O2 dissociation proceeds with low barriers on Au(111) because chemisorbed peroxides (*OOH* and *HOOH*) form and weaken O-O bonds before cleavage, thus allowing activation on low-index planes. DFT-derived O2 dissociation barriers are much lower on bare Pt surfaces, but such surfaces are nearly saturated with CO* during CO oxidation. A dearth of vacant sites causes O2* to react with CO* to form *OOCO* intermediates that undergo O-O cleavage. NO-H2 reactions occur on Pt clusters saturated with NO* and H*; direct NO* dissociation requires vacant

  6. Annealing-induced changes in chemical bonding and surface characteristics of chemical solution deposited Pb0.95La0.05Zr0.54Ti0.46O3 thin films

    Science.gov (United States)

    Batra, Vaishali; Ramana, C. V.; Kotru, Sushma

    2016-08-01

    We report the effect of post deposition annealing temperature (Ta = 550 and 750 °C) on the surface morphology, chemical bonding and structural development of lanthanum doped lead zirconate titanate (Pb0.95La0.05Zr0.54Ti0.46O3; referred to PLZT) thin films prepared using chemical solution deposition method. Atomic force microscopy demonstrates formation of nanocrystallites in the film annealed at Ta = 750 °C. X-ray photoelectron spectroscopy (XPS) analyses indicate that the binding energies (BE) of the Pb 4f, Zr 3d, and Ti 2p doublet experience a positive energy shift at Ta = 750 °C, whereas the BE of O 1s and La 3d doublet show a negative shift with respect to the BE of the films annealed at Ta = 750 °C. Thermal induced crystallization and chemical modification is evident from XPS results. The Ar+ sputtering of the films reveals change in oxidation state and chemical bonding between the constituent atoms, with respect to Ta. Raman spectroscopy used to study phonon-light interactions show shift in longitudinal and transverse optical modes with the change in Ta, confirming the change in phase and crystallinity of these films. The results suggest annealing at Ta = 750 °C yield crystalline perovskite PLZT films, which is essential to obtain photovoltaic response from devices based on such films.

  7. A quantum-chemical validation about the formation of hydrogen bonds and secondary interactions in intermolecular heterocyclic systems

    Directory of Open Access Journals (Sweden)

    Boaz Galdino Oliveira

    2009-08-01

    Full Text Available We have performed a detailed theoretical study in order to understand the charge density topology of the C2H4O···C2H2 and C2H4S···C2H2 heterocyclic hydrogen-bonded complexes. Through the calculations derived from Quantum Theory of Atoms in Molecules (QTAIM, it was observed the formation of hydrogen bonds and secondary interactions. Such analysis was performed through the determination of optimized geometries at B3LYP/6-31G(d,p level of theory, by which is that QTAIM topological operators were computed, such as the electronic density ρ(r, Laplacian Ñ2ρ(r, and ellipticity ε. The examination of the hydrogen bonds has been performed through the measurement of ρ(r, Ñ2ρ(r and ε between (O···H—C and (S···H—C, whereas the secondary interaction between axial hydrogen atoms Hα and carbon of acetylene. In this insight, it was verified the existence of secondary interaction only in C2H4S···C2H2 complex because its structure is propitious to form multiple interactions.

  8. The Different Sensitive Behaviors of a Hydrogen-Bond Acidic Polymer-Coated SAW Sensor for Chemical Warfare Agents and Their Simulants

    Directory of Open Access Journals (Sweden)

    Yin Long

    2015-07-01

    Full Text Available A linear hydrogen-bond acidic (HBA linear functionalized polymer (PLF, was deposited onto a bare surface acoustic wave (SAW device to fabricate a chemical sensor. Real-time responses of the sensor to a series of compounds including sarin (GB, dimethyl methylphosphonate (DMMP, mustard gas (HD, chloroethyl ethyl sulphide (2-CEES, 1,5-dichloropentane (DCP and some organic solvents were studied. The results show that the sensor is highly sensitive to GB and DMMP, and has low sensitivity to HD and DCP, as expected. However, the sensor possesses an unexpected high sensitivity toward 2-CEES. This good sensing performance can’t be solely or mainly attributed to the dipole-dipole interaction since the sensor is not sensitive to some high polarity solvents. We believe the lone pair electrons around the sulphur atom of 2-CEES provide an electron-rich site, which facilitates the formation of hydrogen bonding between PLF and 2-CEES. On the contrary, the electron cloud on the sulphur atom of the HD molecule is offset or depleted by its two neighbouring strong electron-withdrawing groups, hence, hydrogen bonding can hardly be formed.

  9. Impact of post-deposition annealing on interfacial chemical bonding states between AlGaN and ZrO{sub 2} grown by atomic layer deposition

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Gang; Arulkumaran, Subramaniam; Ng, Geok Ing; Li, Yang; Ang, Kian Siong [Novitas, Nanoelectronics Center of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Wang, Hong, E-mail: ewanghong@ntu.edu.sg [Novitas, Nanoelectronics Center of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); CINTRA CNRS/NTU/Thales, UMI 3288, 50 Nanyang Drive (Singapore); Ng, Serene Lay Geok; Ji, Rong [Data Storage Institute, Agency for Science Technology and Research (A-STAR), 5 Engineering Drive 1, 117608 (Singapore); Liu, Zhi Hong [Singapore-MIT Alliance for Research and Technology, 1 CREATE Way, Singapore 138602 (Singapore)

    2015-03-02

    The effect of post-deposition annealing on chemical bonding states at interface between Al{sub 0.5}Ga{sub 0.5}N and ZrO{sub 2} grown by atomic layer deposition (ALD) is studied by angle-resolved x-ray photoelectron spectroscopy and high-resolution transmission electron microscopy. It has been found that both of Al-O/Al 2p and Ga-O/Ga 3d area ratio decrease at annealing temperatures lower than 500 °C, which could be attributed to “clean up” effect of ALD-ZrO{sub 2} on AlGaN. Compared to Ga spectra, a much larger decrease in Al-O/Al 2p ratio at a smaller take-off angle θ is observed, which indicates higher effectiveness of the passivation of Al-O bond than Ga-O bond through “clean up” effect near the interface. However, degradation of ZrO{sub 2}/AlGaN interface quality due to re-oxidation at higher annealing temperature (>500 °C) is also found. The XPS spectra clearly reveal that Al atoms at ZrO{sub 2}/AlGaN interface are easier to get oxidized as compared with Ga atoms.

  10. Zinc phosphate as versatile material for potential biomedical applications Part 1.

    Science.gov (United States)

    Herschke, L; Rottstegge, J; Lieberwirth, I; Wegner, G

    2006-01-01

    Synthetic alpha - and beta -Hopeite, two polymorphs of zinc phosphate tetrahydrates (ZPT) have been synthesized by hydrothermal crystallization from aqueous solution at 20 degrees C and 90 degrees C respectively. Aside from their sub-title crystallographic differences originating from a unique hydrogen bonding pattern, their thermodynamic interrelation has been thoroughfully investigated by means of X-Ray diffraction (XRD) and differential scanning calorimetry (DSC), combined with thermogravimetry (TGA-MS). Using a new heterogeneous step-reaction approach, the kinetics of dehydration of the two forms of ZPT was studied and their corresponding transition temperature determined. Low temperature DRIFT, FT-Raman and (1)H, (31)P MAS-NMR reveal an oriented distortion of the zinc phosphate tetrahedra, due to a characteristic hydrogen bonding pattern and in accordance with the molecular tetrahedral linkage scheme of the phosphate groups. Biogenic Hydroxyapatite (HAP) and one of its metastable precursors, a calcium dihydrogen phosphate dihydrate (DCPD) or Brushite were also obtained and used to underline the resulting variations of chemical reactivity in zinc phosphates.

  11. Magnetovolume and chemical bonding effects of Ni atom in γ’-(Fe1-xNix)4N compounds

    Institute of Scientific and Technical Information of China (English)

    薛德胜; 李发伸

    1997-01-01

    By X-ray diffraction and high pressure Mossbauer spectroscopy, the structure and the hyperfine parameters of Ni substituted γ-Fe4N were investigated. The results of X-ray diffraction indicate that single phase γ’-(Fe1-xNix)4N compounds can be prepared in the composition range of 0≤x≤0.6, and with the increase of Ni content the lattice parameter is fit for the relationship a0(x) = 3.790 5-0.021 57x-0.031 67x2. By high pressure Mossbauer spectra, effects of magnetovolume and chemical bonding of Ni atom on hyperfine magnetic field and isomer shift of iron were distinguished for the first time, and their composition dependences for different lattice sites were studied simultaneously. It is found that the magnetovolume and chemical bonding have different influences on the properties of γ’-(Fe1-xNix)4N, and the latter one plays a key role in the property changes of γ-(Fe1-xNix)4N.

  12. Students' Interdisciplinary Reasoning about "High-Energy Bonds" and ATP

    CERN Document Server

    Dreyfus, Benjamin W; Sawtelle, Vashti; Svoboda, Julia; Turpen, Chandra; Redish, Edward F

    2012-01-01

    Students' sometimes contradictory ideas about ATP (adenosine triphosphate) and the nature of chemical bonds have been studied in the biology and chemistry education literatures, but these topics are rarely part of the introductory physics curriculum. We present qualitative data from an introductory physics course for undergraduate biology majors that seeks to build greater interdisciplinary coherence and therefore includes these topics. In these data, students grapple with the apparent contradiction between the energy released when the phosphate bond in ATP is broken and the idea that an energy input is required to break a bond. We see that students' perceptions of how each scientific discipline bounds the system of interest can influence how they justify their reasoning about a topic that crosses disciplines. This has consequences for a vision of interdisciplinary education that respects disciplinary perspectives while bringing them into interaction in ways that demonstrate consistency amongst the perspectiv...

  13. Financial analysis of phosphate chemical industry listed companies in China%我国磷化工行业上市公司财务分析

    Institute of Scientific and Technical Information of China (English)

    张海波; 刘颖

    2012-01-01

    从财务的角度,对我国磷化工行业主要上市公司2006--2010年度的财务报表分别从偿债能力、营运能力、盈利能力和发展能力四个方面进行了分析。分析结果表明,兴发集团在最近5年内对流动资产的管理水平是同类企业中最高的,偿债能力在不断提高,权益净利率保持稳定,企业的规模也在不断扩大。此外,杜邦分析体系分析表明,兴发集团的权益净利率的波动主要受销售净利率的影响。%Based on financial perspective, 2006--2010 annual financial statement of main listed company of phosphate chemical industry in China are analyzed from the debt paying ability, operation ability, profitability and development ability. The analysis results show that, in recent five years management level of current assets in Xingfa Group is the highest, its solvency is ceaselessly risen, the return rate on equity is stable and the enterprise scale is expanding continually. In addition, the DuPont analysis system shows that the return rate on equity of Xingfa Group is mainly affected by the sales net rates.

  14. Low-temperature setting phosphate ceramics for stabilization of DOE problem low level mixed-waste: I. Material and waste form development

    Energy Technology Data Exchange (ETDEWEB)

    Singh, D.; Wagh, A.; Knox, L. [Argonne National Lab., Argonne, IL (United States); Mayberry, J. [Science Applications International Corp., Idaho Falls, ID (United States)

    1994-03-01

    Chemically bonded phosphate ceramics are proposed as candidates for solidification and stabilization of some of the {open_quotes}problem{close_quotes} DOE low-level mixed wastes at low-temperatures. Development of these materials is crucial for stabilization of waste streams which have volatile species and any use of high-temperature technology leads to generation of off-gas secondary waste streams. Several phosphates of Mg, Al, and Zr have been investigated as candidate materials. Monoliths of these phosphates were synthesized using chemical routes at room or slightly elevated temperatures. Detailed physical and chemical characterizations have been conducted on some of these phosphates to establish their durability. Magnesium ammonium phosphate has shown to possess excellent mechanical and as well chemical properties. These phosphates were also used to stabilize a surrogate ash waste with a loading ranging from 25-35 wt.%. Characterization of the final waste forms show that waste immobilization is due to both chemical stabilization and physical encapsulation of the surrogate waste which is desirable for waste immobilization.

  15. Does dental zinc phosphate cement really shrink in clinical applications?

    Science.gov (United States)

    Liu, Yang; Yu, Hai-Yang

    2009-08-01

    Crowns are cemented onto abutments with adhesives; and zinc phosphate cement is a routine permanent luting agent, which is believed to secure crowns to abutments by non-adhesive micro-mechanical interlocking. Because it has been proven, and the public widely accepts, that zinc phosphate cement forms no chemical bonds with either the crown or the tooth tissue; it is impossible for the cement to attain adequate retention force if it contracts in volume. Assuming that the cement contracts in volume after setting, the prosthesis tends to loose and is doomed to be hampered by fretting damage when it functions during the masticatory cycle; thus the prognosis for the prosthesis is questionable. However, zinc phosphate is popular because of its brilliant clinical record. This paradox between theory and practice indicates that something might be wrong with the standing theory. The most possible problem with previous studies is that their samples' dimensions differ from those that are used clinically, which causes the studies' results, which claim that the cement shrinks, to deviate from clinical results. The real rationale must be that the zinc phosphate cement tends to expand in volume, and thus mechanically fasten the crown to the abutment.

  16. Exploring Conceptual Frameworks of Models of Atomic Structures and Periodic Variations, Chemical Bonding, and Molecular Shape and Polarity: A Comparison of Undergraduate General Chemistry Students with High and Low Levels of Content Knowledge

    Science.gov (United States)

    Wang, Chia-Yu; Barrow, Lloyd H.

    2013-01-01

    The purpose of the study was to explore students' conceptual frameworks of models of atomic structure and periodic variations, chemical bonding, and molecular shape and polarity, and how these conceptual frameworks influence their quality of explanations and ability to shift among chemical representations. This study employed a purposeful sampling…

  17. The solid phase extraction of some metal ions using palladium nanoparticles attached to silica gel chemically bonded by silica-bonded N-propylmorpholine as new sorbent prior to their determination by flame atomic absorption spectroscopy.

    Science.gov (United States)

    Ghaedi, M; Rezakhani, M; Khodadoust, S; Niknam, K; Soylak, M

    2012-01-01

    In this research at first palladium nanoparticle attached to a new chemically bonded silica gel has been synthesized and has been characterized with different techniques such as X-ray diffraction (XRD), fourier transform infrared (FT-IR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Then, this new sorbent (chemically modified silica gel with N-propylmorpholine (PNP-SBNPM)) was efficiently used for preconcentration of some metal ions in various food samples. The influence of effective variables including mass of sorbent, flow rate, pH of sample solutions and condition of eluent such as volume, type and concentration on the recoveries of understudy metal ions were investigated. Following the optimization of variables, the interfering effects of some foreign ions on the preconcentration and determination of the investigated metal ions described. At optimum values of variables, all investigated metal ions were efficiently recovered with efficiency more than 95%, relative standard deviation (RSD) between 2.4 and 2.8, and detection limit in the range of 1.4-2.7 ng mL⁻¹. The present method is simple and rapidly applicable for the determination of the understudied metal ions (ng mL⁻¹) in different natural food samples.

  18. The Solid Phase Extraction of Some Metal Ions Using Palladium Nanoparticles Attached to Silica Gel Chemically Bonded by Silica-Bonded N-Propylmorpholine as New Sorbent prior to Their Determination by Flame Atomic Absorption Spectroscopy

    Directory of Open Access Journals (Sweden)

    M. Ghaedi

    2012-01-01

    Full Text Available In this research at first palladium nanoparticle attached to a new chemically bonded silica gel has been synthesized and has been characterized with different techniques such as X-ray diffraction (XRD, fourier transform infrared (FT-IR, transmission electron microscopy (TEM, and scanning electron microscopy (SEM. Then, this new sorbent (chemically modified silica gel with N-propylmorpholine (PNP-SBNPM was efficiently used for preconcentration of some metal ions in various food samples. The influence of effective variables including mass of sorbent, flow rate, pH of sample solutions and condition of eluent such as volume, type and concentration on the recoveries of understudy metal ions were investigated. Following the optimization of variables, the interfering effects of some foreign ions on the preconcentration and determination of the investigated metal ions described. At optimum values of variables, all investigated metal ions were efficiently recovered with efficiency more than 95%, relative standard deviation (RSD between 2.4 and 2.8, and detection limit in the range of 1.4–2.7 ng mL−1. The present method is simple and rapidly applicable for the determination of the understudied metal ions (ng mL−1 in different natural food samples.

  19. Structural, quantum chemical, vibrational and thermal studies of a hydrogen bonded zwitterionic co-crystal (nicotinic acid: pyrogallol)

    Science.gov (United States)

    Prabha, E. Arockia Jeya Yasmi; Kumar, S. Suresh; Athimoolam, S.; Sridhar, B.

    2017-02-01

    In the present work, a new co-crystal of nicotinic acid with pyrogallol (NICPY) has been grown in the zwitterionic form and the corresponding structural, vibrational, thermal, solubility and anti-cancer characteristics have been reported. The single crystal X-ray diffraction analysis confirms that the structural molecular packing of the crystal stabilized through N-H⋯O and O-H⋯O hydrogen bond. The stabilization energy of the hydrogen bond motifs were calculated in the solid state. Vibrational spectral studies such as Fourier transform-infrared (FT-IR) and FT-Raman were adopted to understand the zwitterionic co-crystalline nature of the compound, which has been compared with theoretically calculated vibrational frequencies. The thermal stability of the grown co-crystal was analyzed by TG/DTA study. The solubility of the NICPY co-crystal was investigated in water at different temperature and compared with that of the nicotinic acid, which is the parent compound of NICPY co-crystal. The grown crystals were treated with human cervical cancer cell line (HeLa) to analyze the cytotoxicity of NICPY crystals and compared with the parent compound, which shows that NICPY has moderate activity against human cervical cancer cell line.

  20. Fabrication of graphene oxide-modified chitosan for controlled release of dexamethasone phosphate

    Science.gov (United States)

    Sun, Huanghui; Zhang, Lingfan; Xia, Wei; Chen, Linxiao; Xu, Zhizhen; Zhang, Wenqing

    2016-07-01

    Functionalized graphene oxide with its unique physical and chemical properties is widely applied in biomaterials, especially in drug carrier materials. In the past few years, a number of different drugs have been loaded on functionalized graphene oxide via π-π stacking and hydrophobic interactions. The present report described a new approach, dexamethasone phosphate successfully loaded onto graphene oxide-chitosan nanocomposites as drug carrier materials by covalent bonding of phosphate ester linkage. Compared with the graphene oxide-chitosan nanocomposites that dexamethasone phosphate was loaded on via simple physical attachment, covalently linked composites as drug carrier materials were more biocompatible which effectively reduced the burst release of drug, and controlled the release of drug in different pH conditions.

  1. A model for biodegradation of composite materials made of polyesters and tricalcium phosphates.

    Science.gov (United States)

    Pan, Jingzhe; Han, Xiaoxiao; Niu, Wenjuan; Cameron, Ruth E

    2011-03-01

    A saturation behaviour has been observed when incorporating tricalcium phosphate (TCP) in various polyesters to control the degradation rate. This paper presents an understanding of this behaviour using a mathematical model. The coupled process of hydrolysis reaction of the ester bonds, acid dissociation of the carboxylic end groups, dissolution of the calcium phosphates and buffering reactions by the dissolved phosphate ions is modelled together using a set of differential equations. Two non-dimensional groups of the material and chemical parameters are identified which control the degradation rate of the composites. An effectiveness map is established to show the conditions under which incorporating TCP into polyesters is effective, saturated or ineffective. Comparisons are made between the model predictions and existing experimental data in the literature. The map provides a useful tool to guide the design of polyester/TCP composites for tissue engineering and orthopaedic fixation applications.

  2. 40 CFR 721.3080 - Substituted phosphate ester (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted phosphate ester (generic... Substances § 721.3080 Substituted phosphate ester (generic). (a) Chemical substances and significant new uses subject to reporting. (1) The chemical substance identified generically as a substituted phosphate...

  3. 磷酸镁胶凝材料基体与玻璃纤维筋的粘结性能%Bond behavior of magnesium phosphate cement matrix and glass fiber bar

    Institute of Scientific and Technical Information of China (English)

    周序洋; 杨建明; 王进

    2012-01-01

    为研究磷酸镁胶凝材料(MPC)基体与玻璃纤维筋的粘结性能,测试了玻璃纤维筋在MPC基体中的拉拔力.结果表明:自制无机胶能较好渗入玻璃纤维筋内部,并将纤维丝牢固地粘结在一起,玻璃纤维筋的轴向拉力显著提高;用掺入适量死烧氧化镁粉的无机胶浸涂玻璃纤维筋,可明显增大玻璃纤维筋在MPC基体中的拉拔力;适量水玻璃可使MPC的结构更加致密,其中玻璃纤维筋的拉拔力亦适当提高;随着玻璃纤维筋埋置长度的增加和MPC基体龄期的延长,玻璃纤维筋的拉拔力逐步提高;存在最佳的玻璃纤维筋埋置长度使玻璃纤维筋拉拔破坏时的拉拔力达到最大;经优化设计的玻璃纤维筋在MPC基体中的拉拔力高于在环氧树脂基体中的拉拔力.%Bond behaviors of magnesium phosphate cement (MPC) matrix with glass fiber bundle ( GFB) were investigated through measuring pullout force of GFB in MPC. The results show that the self-made inorganic adhesive can permeate into glass fibrils with markedly improved axial tensile strength of GFB. The pull-out force of GFB can be increased by mixing magnesium oxide powder. The micro structure of MPC paste is compacted by water glass to achieve pull-out force of GFB. The pull-out force can be effectively improved by the increasing of GFB length and MPC age. It can be confirmed that the optimized embedded length of GFB would exist and the maximum pull-out forces could be achieved in pullout destructive form. The pull-out force of GFB in MPC matrix with optimized embedded length is greater than that in epoxy resin matrix.

  4. Hydrogen bond driven chemical reactions: Beckmann rearrangement of cyclohexanone oxime into epsilon-caprolactam in supercritical water.

    Science.gov (United States)

    Boero, Mauro; Ikeshoji, Tamio; Liew, Chee Chin; Terakura, Kiyoyuki; Parrinello, Michele

    2004-05-26

    Recent experiments have shown that supercritical water (SCW) has the ability to accelerate and make selective synthetic organic reactions, thus replacing the common but environmentally harmful acid and basic catalysts. In an attempt to understand the intimate mechanism behind this observation, we analyze, via first-principles molecular dynamics, the Beckmann rearrangement of cyclohexanone oxime into epsilon-caprolactam in supercritical water, for which accurate experimental evidence has been reported. Differences in the wetting of the hydrophilic parts of the solute, enhanced by SCW, and the disrupted hydrogen bond network are shown to be crucial in triggering the reaction and in making it selective. Furthermore, the enhanced concentrations of H(+) in SCW play an important role in starting the reaction.

  5. Stereocontrolled Synthesis of β-Lactams within [2]Rotaxanes: Showcasing the Chemical Consequences of the Mechanical Bond.

    Science.gov (United States)

    Martinez-Cuezva, Alberto; Lopez-Leonardo, Carmen; Bautista, Delia; Alajarin, Mateo; Berna, Jose

    2016-07-20

    The intramolecular cyclization of N-benzylfumaramide [2]rotaxanes is described. The mechanical bond of these substrates activates this transformation to proceed in high yields and in a regio- and diastereoselective manner, giving interlocked 3,4-disubstituted trans-azetidin-2-ones. This activation effect markedly differs from the more common shielding protection of threaded functions by the macrocycle, in this case promoting an unusual and disfavored 4-exo-trig ring closure. Kinetic and synthetic studies allowed us to delineate an advantageous approach toward β-lactams based on a two-step, one-pot protocol: an intramolecular ring closure followed by a thermally induced dethreading step. The advantages of carrying out this cyclization in the confined space of a benzylic amide macrocycle are attributed to its anchimeric assistance.

  6. New sol–gel refractory coatings on chemically-bonded sand cores for foundry applications to improve casting surface quality

    DEFF Research Database (Denmark)

    Nwaogu, Ugochukwu Chibuzoh; Poulsen, T.; Stage, R.K.

    2011-01-01

    Foundry refractory coatings protect bonded sand cores and moulds from producing defective castings during the casting process by providing a barrier between the core and the liquid metal. In this study, new sol–gel refractory coating on phenolic urethane cold box (PUCB) core was examined....... The coating density, viscosity, moisture content and wet and dry weight of the coating were evaluated on cores that had been coated at three different dip-coating times. The coating coverage, surface appearance and depth of penetration into the cores were examined with a Stereomicroscope. Gray iron castings...... were produced with sol-gel coated and uncoated cores and the results were related to the coating properties. The casting results were also compared with castings made with cores coated with commercial alcohol-based and water-based foundry coatings. The analyses show that castings produced with sol...

  7. An Effective Hamiltonian Molecular Orbital-Valence Bond (MOVB) Approach for Chemical Reactions Applied to the Nucleophilic Substitution Reaction of Hydrosulfide Ion and Chloromethane.

    Science.gov (United States)

    Song, Lingchun; Mo, Yirong; Gao, Jiali

    2009-01-01

    An effective Hamiltonian mixed molecular orbital and valence bond (EH-MOVB) method is described to obtain an accurate potential energy surface for chemical reactions. Building upon previous results on the construction of diabatic and adiabatic potential surfaces using ab initio MOVB theory, we introduce a diabatic-coupling scaling factor to uniformly scale the ab initio off-diagonal matrix element H(12) such that the computed energy of reaction from the EH-MOVB method is in agreement with the target value. The scaling factor is very close to unity, resulting in minimal alteration of the potential energy surface of the original MOVB model. Furthermore, the relative energy between the reactant and product diabatic states in the EH-MOVB method can be improved to match the experimental energy of reaction. A key ingredient in the EH-MOVB theory is that the off-diagonal matrix elements are functions of all degrees of freedom of the system and the overlap matrix is explicitly evaluated. The EH-MOVB method has been applied to the nucleophilic substitution reaction between hydrosulfide and chloromethane to illustrate the methodology and the results were matched to reproduce the results from ab initio valence bond self-consistent valence bond (VBSCF) calculations. The diabatic coupling (the off-diagonal matrix element in the generalized secular equation) has small variations along the minimum energy reaction path in the EH-MOVB model, whereas it shows a maximum value at the transition state and has nearly zero values in the regions of the ion-dipole complexes from VBSCF calculations. The difference in the diabatic coupling stabilization is attributed to the large overlap integral in the computationally efficient MOVB method.

  8. Effect of Si-H bond on the gas-phase chemistry of trimethylsilane in the hot wire chemical vapor deposition process.

    Science.gov (United States)

    Shi, Y J; Li, X M; Toukabri, R; Tong, L

    2011-09-22

    The effect of the Si-H bond on the gas-phase reaction chemistry of trimethylsilane in the hot-wire chemical vapor deposition (HWCVD) process has been studied by examining its decomposition on a hot tungsten filament and the secondary gas-phase reactions in a reactor using a soft laser ionization source coupled with mass spectrometry. Trimethylsilane decomposes on the hot filament via Si-H and Si-CH(3) bond cleavages. A short-chain mechanism is found to dominate in the secondary reactions in the reactor. It has been shown that the hydrogen abstractions of both Si-H and C-H occur simultaneously, with the abstraction of Si-H being favored. Tetramethylsilane and hexamethyldisilane are the two major products formed from the radical recombination reactions in the termination steps. Three methyl-substituted disilacyclobutane molecules, i.e., 1,3-dimethyl-1,3-disilacyclobutane, 1,1,3-trimethyl-1,3-disilacyclobutane, and 1,1,3,3-tetramethyl-1,3-disilacyclobutane are also produced in reactor from the cycloaddition reactions of methyl-substituted silene species. Compared to tetramethylsilane and hexamethyldisilane, a common feature with trimethylsilane is that the short-chain mechanism still dominates. However, a more active involvement of the reactive silene intermediates has been found with trimethylsilane.

  9. Synthesis, structure, spectral properties and DFT quantum chemical calculations of 4-aminoazobenzene dyes. Effect of intramolecular hydrogen bonding on photoisomerization

    Science.gov (United States)

    Georgiev, Anton; Bubev, Emil; Dimov, Deyan; Yancheva, Denitsa; Zhivkov, Ivaylo; Krajčovič, Jozef; Vala, Martin; Weiter, Martin; Machkova, Maria

    2017-03-01

    In this paper three different "push-pull" 4-aminoazobenzene dyes have been synthesized in order to characterize their photochromic behavior in different solvents. The molecular geometry was optimized by DFT/B3LYP functional combined with the standard 6-31 + G(d,p) basis set for trans (E) and cis (Z) isomers and the energy levels of HOMO and LUMO frontier orbitals were computed using IEFPCM solvation in CHCl3 and DMF. The calculated results were compared to the experimental optical band gap and HOMO values of cyclic voltammetry. The intramolecular six-membered hydrogen bond was formed in both isomers of the synthesized dyes. The thermodynamic parameters such as total electronic energy E (RB3LYP), enthalpy H298 (sum of electronic and thermal enthalpies), free Gibbs energy G298 (sum of electronic and thermal free Gibbs energies) and dipole moment μ were computed for trans (E) and cis (Z) isomers in order to estimate the ΔEtrans → cis, Δμtrans → cis, ΔHtrans → cis, ΔGtrans → cis and ΔStrans → cis values. The NBO analysis was performed in order to understand the intramolecular charge transfer and energy of resonance stabilization. The solvatochromic shift was evaluated by UV-VIS spectroscopy in CHCl3 (nonpolar), EtOH (polar protic) and DMF (polar aprotic) solvents to determine the electron withdrawing and donating properties of the substituents on electron transitions energy. Through the increasing solvent polarity a strong bathochromic shift is observed. The photoisomerization experiments have been performed in two solvents CHCl3 (nonpolar) and DMF (polar aprotic) by UV light irradiation with λ = 365 nm at equal concentrations and time of illuminations. The electronic spectra were computed by TD-DFT after geometry optimization using IEFPCM solvation in CHCl3 and DMF. The degree of photoisomerization was calculated for the three azo chromophores in both solvents. By using first derivative of the UV-VIS spectra it was possible to resolve the overlapped

  10. Comparison of the Shear Bond Strength of Light-cured and Chemically-cured Resin Adhesive%光固化和化学固化树脂粘接剂剪切强度的对比研究

    Institute of Scientific and Technical Information of China (English)

    张隆祺; 王野平

    2001-01-01

    Objective To compare the shear bond strength of light-cured and chemically-cured resin adhesive. Methods Twenty recently extracted human premolars were randomly divided into two groups of 10 each.: Group A, using the chemically-cured resin adhesive (Jing Jinenamel adhesive) and Group B, using the light-cured resin adhesive (Transbond XT,3M Unitek). The brackets were bonded to prepared enamel surfaces and the samples were placed in a water bath at 37℃ for 24 hours, then measured the shear bond strength and assessed the remaining adhesive after debonded. Results The shear bond strength and assessing the remaining adhesive after debonded both had no statistical significanct difference between two adhesives. Conclusion The light-cured and the chemically-cured resin adhesive both have strong bond strength, but the light-cured resin adhesive has the advantage to offer more sufficient time for positioning and bonding the brackets, so it is recommended for using.%-05)。结论光固化和化学固化树脂粘接剂均具有较强的粘接强度,但光固化树脂粘接剂能够为托槽的定位和粘接提供充足的时间,推荐使用。

  11. Probing the structures and chemical bonding of boron-boronyl clusters using photoelectron spectroscopy and computational chemistry: B4(BO)(n)- (n = 1-3).

    Science.gov (United States)

    Chen, Qiang; Zhai, Hua-Jin; Li, Si-Dian; Wang, Lai-Sheng

    2012-07-28

    The electronic and structural properties of a series of boron oxide clusters, B(5)O(-), B(6)O(2)(-), and B(7)O(3)(-), are studied using photoelectron spectroscopy and density functional calculations. Vibrationally resolved photoelectron spectra are obtained, yielding electron affinities of 3.45, 3.54, and 4.94 eV for the corresponding neutrals, B(5)O, B(6)O(2), and B(7)O(3), respectively. Structural optimizations show that these oxide clusters can be formulated as B(4)(BO)(n)(-) (n = 1-3), which involve boronyls coordinated to a planar rhombic B(4) cluster. Chemical bonding analyses indicate that the B(4)(BO)(n)(-) clusters are all aromatic species with two π electrons.

  12. Probing the structures and chemical bonding of boron-boronyl clusters using photoelectron spectroscopy and computational chemistry: B4(BO)n- (n = 1-3)

    Science.gov (United States)

    Chen, Qiang; Zhai, Hua-Jin; Li, Si-Dian; Wang, Lai-Sheng

    2012-07-01

    The electronic and structural properties of a series of boron oxide clusters, B5O-, B6O2-, and B7O3-, are studied using photoelectron spectroscopy and density functional calculations. Vibrationally resolved photoelectron spectra are obtained, yielding electron affinities of 3.45, 3.54, and 4.94 eV for the corresponding neutrals, B5O, B6O2, and B7O3, respectively. Structural optimizations show that these oxide clusters can be formulated as B4(BO)n- (n = 1-3), which involve boronyls coordinated to a planar rhombic B4 cluster. Chemical bonding analyses indicate that the B4(BO)n- clusters are all aromatic species with two π electrons.

  13. Effects of combination modes of favorable growth unit of Al(OH)3 crystals precipitating on Van der Waals and chemical bond force

    Institute of Scientific and Technical Information of China (English)

    WU Zheng-ping; CHEN Qi-yuan; YIN Zhou-lan; LI Jie

    2005-01-01

    The dipole moment, total energy, atomic charge, orbital population and orbital energy of four representative combination models of the favorable growth unit Al6 (OH)18 (H2O)6 of Al(OH)3 crystals precipitating are calculated by ab initio at RHF/STO-3G, RHF/3-21G, RHF/6-31G levels and DFT at RB3LYP/STO-3G, RB3LYP/3-21G, RB3LYP/6-31G levels with Dipole & Sphere solvent model. The effect of various combination models on Van der Waals force is analyzed using dipole moment and molecular radius, and that on chemical bond force is analyzed using total energy, orbital population and orbital energy.

  14. The effects of reasoning, use of models, sex type, and their interactions on posttest achievement in chemical bonding after constant instruction

    Science.gov (United States)

    Staver, John R.; Halsted, Douglas A.

    The purpose of the authors in this study was to determine the effects of reasoning, use of models during testing, and sex type on posttest achievement in chemical bonding under controlled instruction. Eighty-four high school students taking chemistry were randomly assigned within their classes to models and no models groups for the posttest. Reasoning capabilities were assessed by the Piagetian Logical Operations Test (PLOT) (Staver & Gabel, JRST, Vol. 16, No. 6, 1979), prior to instruction. All students then received the same instruction on chemical bonding which included teacher demonstrations of concepts with three-dimensional molecular models, interspersed teacher questions during the introduction and development of concepts, student manipulation of three-dimensional molecular models during laboratory experiments, and text reading assignments on concepts prior to their instruction in class. The posttest on molecular geometry and shape contained three sections requiring memory and application (Bloom, Taxonomy of educational objective, handbook I: Cognitive domain. New York: David McKay, 1956). Data were analyzed by regression (Nie et al., Statistical package for the social sciences, 2nd ed. New York: McGraw-Hill, 1975). Results indicate that reasoning accounted for a significant portion (p 0.05) portion of the variance on total scores or any section of posttest. The three-way interaction of reasoning, model usage, and sex type accounted for a significant portion (p < 0.05) of the variance in total scores, and in the memory and application sections of the posttest. Discussion focused on the results, conclusions, and implications for science teaching.

  15. Facile Synthesis of Layer Structured GeP3/C with Stable Chemical Bonding for Enhanced Lithium-Ion Storage

    Science.gov (United States)

    Qi, Wen; Zhao, Haihua; Wu, Ying; Zeng, Hong; Tao, Tao; Chen, Chao; Kuang, Chunjiang; Zhou, Shaoxiong; Huang, Yunhui

    2017-01-01

    Recently, metal phosphides have been investigated as potential anode materials because of higher specific capacity compared with those of carbonaceous materials. However, the rapid capacity fade upon cycling leads to poor durability and short cycle life, which cannot meet the need of lithium-ion batteries with high energy density. Herein, we report a layer-structured GeP3/C nanocomposite anode material with high performance prepared by a facial and large-scale ball milling method via in-situ mechanical reaction. The P-O-C bonds are formed in the composite, leading to close contact between GeP3 and carbon. As a result, the GeP3/C anode displays excellent lithium storage performance with a high reversible capacity up to 1109 mA h g−1 after 130 cycles at a current density of 0.1 A g−1. Even at high current densities of 2 and 5 A g−1, the reversible capacities are still as high as 590 and 425 mA h g−1, respectively. This suggests that the GeP3/C composite is promising to achieve high-energy lithium-ion batteries and the mechanical milling is an efficient method to fabricate such composite electrode materials especially for large-scale application. PMID:28240247

  16. Chemical bond approach to optical properties of some flash evaporated Se100-XSbX chalcogenide alloys

    Science.gov (United States)

    Muiva, C. M.; Sathiaraj, T. S.; Mwabora, J. M.

    2012-07-01

    Amorphous thin films of Se100 - XSbX (X = 1, 5, 10, 15 and 20) were synthesized by flash evaporation of the premelt quenched bulk samples. The optical properties were investigated from spectrophotometric measurements in the UV-VIS-NIR spectral region using Swanepoel's standard envelope method and related techniques. The optical band gap energy (Egopt) was evaluated from the Wemple-Didomenico (WDD) single oscillator model and Tauc's extrapolation method in the region where the absorption coefficient, α ≥ 104 cm-1. The observed values of Egopt and oscillator energy Eo were found to decrease monotonously with increasing Sb additive. The complex dielectric constant (ɛ), Urbach energy (Eu), optical conductivity (σ), plasma frequency (ωp) and lattice dielectric constant (ɛL) were deduced for each alloy composition. The complex refractive index (n) fitted well to Sellmeier function which can allow extrapolation of n outside the measured spectral range. The observed changes in optical parameters with Sb content were explained on the basis of increased defect states and changes in cohesive energy indicators (average heat of atomization (Hs), mean coordination number and average single bond energy (Hs/).

  17. Invention of stimulus-responsive peptide-bond-cleaving residue (Spr) and its application to chemical biology tools.

    Science.gov (United States)

    Shigenaga, Akira; Yamamoto, Jun; Kohiki, Taiki; Inokuma, Tsubasa; Otaka, Akira

    2017-01-19

    Elucidation of biological functions of peptides and proteins is essential for understanding peptide/protein-related biological events and developing drugs. Caged peptides and proteins that release a parent active peptide/protein by photo-irradiation have successfully been employed to elucidate the functions. Whereas the usual caged peptide/protein enables conversion of an inactive form to an active form (OFF-to-ON conversion) by photo-induced deprotection, photo-triggered main chain cleavage is reported to be applicable to ON-to-OFF conversion. These peptides and proteins are photo-responsive; however, if peptides and proteins could respond to other stimuli such as disease-related environment or enzymes, their range of application should be widened. To convert the photo-responsive peptide/protein into other stimulus-responsive peptide/protein, quite laborious de novo design and synthesis of the stimulus-responsive unit are required. In this context, we designed a stimulus-responsive peptide-bond-cleaving residue (Spr) in which the stimuli available for the main chain cleavage vary according to the choice of protecting groups on the residue. In this review, design and synthesis of Spr are introduced, and challenges to apply Spr to other fields to enable, for example, functional control, localization control, delivery of cargos, labeling of a protein of interest in living cells, and identification of target proteins of bioactive ligands are discussed. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.

  18. Chemically fixed p-n heterojunctions for polymer electronics by means of covalent B-F bond formation

    Science.gov (United States)

    Hoven, Corey V.; Wang, Huiping; Elbing, Mark; Garner, Logan; Winkelhaus, Daniel; Bazan, Guillermo C.

    2010-03-01

    Widely used solid-state devices fabricated with inorganic semiconductors, including light-emitting diodes and solar cells, derive much of their function from the p-n junction. Such junctions lead to diode characteristics and are attained when p-doped and n-doped materials come into contact with each other. Achieving bilayer p-n junctions with semiconducting polymers has been hindered by difficulties in the deposition of thin films with independent p-doped and n-doped layers. Here we report on how to achieve permanently fixed organic p-n heterojunctions by using a cationic conjugated polyelectrolyte with fluoride counteranions and an underlayer composed of a neutral conjugated polymer bearing anion-trapping functional groups. Application of a bias leads to charge injection and fluoride migration into the neutral layer, where irreversible covalent bond formation takes place. After the initial charging and doping, one obtains devices with no delay in the turn on of light-emitting electrochemical behaviour and excellent current rectification. Such devices highlight how mobile ions in organic media can open opportunities to realize device structures in ways that do not have analogies in the world of silicon and promise new opportunities for integrating organic materials within technologies now dominated by inorganic semiconductors.

  19. A periodic Energy Decomposition Analysis (pEDA) method for the Investigation of Chemical Bonding in Extended Systems

    CERN Document Server

    Raupach, Marc

    2015-01-01

    The development and first applications of a new periodic energy decomposition analysis (pEDA) scheme for extended systems based on the Kohn-Sham approach to density functional theory are described. The pEDA decomposes the binding energy between two fragments (e.g. the adsorption energy of a molecule on a surface) into several well-defined terms: preparation, electrostatic and dispersion interaction, Pauli repulsion and orbital relaxation energies. The pEDA presented here for an AO-based implementation can handle restricted and unrestricted fragments for 0D to 3D systems considering periodic boundary conditions with and without the determination of fragment occupations. For the latter case, reciprocal space sampling is enabled. The new method gives comparable results to established schemes for molecular systems and shows good convergence with respect to the basis set (TZ2P), the integration accuracy and k-space sampling. Four typical bonding scenarios for surface adsorbate complexes were chosen to highlight th...

  20. Rod like attapulgite/poly(ethylene terephthalate nanocomposites with chemical bonding between the polymer chain and the filler

    Directory of Open Access Journals (Sweden)

    Q. Fu

    2012-08-01

    Full Text Available Poly(ethylene terephthalate (PET nanocomposites containing rod-like silicate attapulgite (AT were prepared via in situ polymerization. It is presented that PET chains identical to the matrix have been successfully grafted onto simple organically pre-modified AT nanorods (MAT surface during the in situ polymerization process. The covalent bonding at the interface was confirmed by Fourier transform infrared spectroscopy (FTIR and thermogravimetric analysis (TGA. The content of grafted PET polymer on the surface of MAT was about 26 wt%. This high grafting density greatly improved the dispersion of fillers, interfacial adhesion as well as the significant confinement of the segmental motion of PET, as compared to the nanocomposites of PET/pristine AT (PET/AT. Owing to the unique interfacial structure in PET/MAT composites, their thermal and mechanical properties have been greatly improved. Compared with neat PET, the elastic modulus and the yield strength of PET/MAT were significantly improved by about 39.5 and 36.8%, respectively, by incorporating only 2 wt % MAT. Our work provides a novel route to fabricate advanced PET nanocomposites using rod-like attapulgite as fillers, which has great potential for industrial applications.

  1. Reaction dynamics. Extremely short-lived reaction resonances in Cl + HD (v = 1) → DCl + H due to chemical bond softening.

    Science.gov (United States)

    Yang, Tiangang; Chen, Jun; Huang, Long; Wang, Tao; Xiao, Chunlei; Sun, Zhigang; Dai, Dongxu; Yang, Xueming; Zhang, Dong H

    2015-01-02

    The Cl + H2 reaction is an important benchmark system in the study of chemical reaction dynamics that has always appeared to proceed via a direct abstraction mechanism, with no clear signature of reaction resonances. Here we report a high-resolution crossed-molecular beam study on the Cl + HD (v = 1, j = 0) → DCl + H reaction (where v is the vibrational quantum number and j is the rotational quantum number). Very few forward scattered products were observed. However, two distinctive peaks at collision energies of 2.4 and 4.3 kilocalories per mole for the DCl (v' = 1) product were detected in the backward scattering direction. Detailed quantum dynamics calculations on a highly accurate potential energy surface suggested that these features originate from two very short-lived dynamical resonances trapped in the peculiar H-DCl (v' = 2) vibrational adiabatic potential wells that result from chemical bond softening. We anticipate that dynamical resonances trapped in such wells exist in many reactions involving vibrationally excited molecules.

  2. Combined analysis of chemical bonding in a Cu(II) dimer using QTAIM, Voronoi tessellation and Hirshfeld surface approaches.

    Science.gov (United States)

    Vologzhanina, Anna V; Kats, Svitlana V; Penkova, Larisa V; Pavlenko, Vadim A; Efimov, Nikolay N; Minin, Vadim V; Eremenko, Igor L

    2015-10-01

    Interaction of 1-(1H-pyrazol-5-yl)ethanone oxime (H2PzOx) with copper(II) chloride in the presence of pyridine afforded a binuclear discrete [Cu2(HPzOx)2Cl2py2] complex, which was characterized by Fourier transform-IR and electron paramagnetic resonance (EPR) spectra, magnetochemistry and high-resolution X-ray diffraction experiments. Multipole refinement of X-ray diffraction data and density-functional theory (DFT) calculations of an isolated molecule allowed charge and spin distributions to be obtained for this compound. Magnetochemistry data, EPR spectra and DFT calculations of an isolated molecule show antiferromagnetic coupling between copper(II) ions. The spin distribution suggests an exchange pathway via the bridging pyrazole ring in the equatorial plane of the CuN4Cl coordination polyhedron, thus providing support for the classical superexchange mechanism; the calculated value of the magnetic coupling constant -2J is equal to 220 cm(-1), which compares well with the experimental value of 203 ± 2 cm(-1). Chemical connectivity was derived by Bader's 'quantum theory of atoms in molecules' and compared with Voronoi tessellation and Hirshfeld surface representations of crystal space. All methodologies gave a similar qualitative and semi-quantitative description of intra- and intermolecular connectivity.

  3. Hydrogen bonding-driven rheological modulation of chemically reduced graphene oxide/poly(vinyl alcohol) suspensions and its application in electrospinning

    Science.gov (United States)

    Tan, Yeqiang; Song, Yihu; Zheng, Qiang

    2012-10-01

    Rheology of graphene oxide (GO) and chemically reduced graphene oxide (RGO) nanosheets suspended in poly(vinyl alcohol) (PVA) solution were investigated by altering nanosheet loading and reduction time of RGO in a wide range. A small amount (0.5 wt%) of GO and RGO in the dilute regime of filler resulted in a threefold increase and a fourfold decrease in steady viscosity at 0.01 s-1, respectively; increasing GO and RGO loadings in the semi-dilute regime of filler caused steady viscosity to increase to different degrees. Meanwhile, the steady viscosity of the suspension decreased gradually by more than one order of magnitude with increasing reduction time of RGO. By characterizing the microstructure in suspensions, the style and relative density of H-bonding between PVA chains and nanosheets were confirmed to account for the suspension rheology. Modulation of viscosity in a wide range via simply control of the loading and reduction time of RGO was hydrogen bonding-driven, which was successfully applied to electrospinning to prepare nanocomposite nanofibers. The addition of 1 wt% GO and RGO with respect to the polymer mass significantly improved PVA fibrous uniformity and fineness, and the spinnable concentration range of PVA was greatly broadened from (8.5-11.3 wt%) to (5-18 wt%). Meanwhile, the thermal stability of the nanofibers was also enhanced by GO or RGO addition.Rheology of graphene oxide (GO) and chemically reduced graphene oxide (RGO) nanosheets suspended in poly(vinyl alcohol) (PVA) solution were investigated by altering nanosheet loading and reduction time of RGO in a wide range. A small amount (0.5 wt%) of GO and RGO in the dilute regime of filler resulted in a threefold increase and a fourfold decrease in steady viscosity at 0.01 s-1, respectively; increasing GO and RGO loadings in the semi-dilute regime of filler caused steady viscosity to increase to different degrees. Meanwhile, the steady viscosity of the suspension decreased gradually by more than

  4. Contribution of Chemical Bonding to the Force in Atomic Force Microscopy%原子力显微镜中化学成键对力的贡献

    Institute of Scientific and Technical Information of China (English)

    李娜; 陈曦; 薛其坤

    2014-01-01

    迄今非接触原子力显微镜已经成为一个非常强大的工具。它不仅能够得到表面的原子周期结构,还能给出分子内部的化学键信息。针尖和样品之间的相互作用是原子力显微镜的有效信号,主要包括三种,即范德瓦尔斯相互作用、静电相互作用和化学键相互作用。本文在生长于Si(111)-7×7的铅薄膜上测量了针尖和样品之间的化学键相互作用。通过获取该相互作用随偏压的变化,并且利用抛物线拟合有效局域接触势的位置,我们发现它是随着针尖和样品之间距离的增大而减小的。这种趋势来自于针尖和样品之间波函数的交叠。从而可以得到电子的衰减长度。我们还测量到了该衰减长度随着铅薄膜厚度的变化会发生振荡,这种振荡归因于平顶楔形铅岛内电子的量子尺寸效应。%Non-contact atomic force microscope (NC-AFM) has become a powerful tool. It can provide the atomic structure and chemical bonding information at the atomic scale. Three kinds of tip-sample interactions are often concerned: including van der Waals interaction, electrostatic interaction, and chemical bonding interaction. In this work, the chemical bonding interaction between the tip and a Pb film is clearly demonstrated by NC-AFM based on a Q-plus force sensor. The tip-sample interaction energy versus the bias voltage was obtained and fitted by a parabolic function to find the effective local contact potential difference, which decreased with increasing tip-sample distance. Such a trend is caused by the wave function overlap. Thus, the decay length of the electron wave function was estimated. Oscillation of the decay length with film thickness was also observed, which can be attributed to the thickness-dependent quantum wel states in the Pb islands.

  5. Removal of arsenic, phosphates and ammonia from well water using electrochemical/chemical methods and advanced oxidation: a pilot plant approach.

    Science.gov (United States)

    Orescanin, Visnja; Kollar, Robert; Nad, Karlo; Halkijevic, Ivan; Kuspilic, Marin; Findri Gustek, Stefica

    2014-01-01

    The purpose of this work was to develop a pilot plant purification system and apply it to groundwater used for human consumption, containing high concentrations of arsenic and increased levels of phosphates, ammonia, mercury and color. The groundwater used was obtained from the production well in the Vinkovci County (Eastern Croatia). Due to a complex composition of the treated water, the purification system involved a combined electrochemical treatment, using iron and aluminum electrode plates with simultaneous ozonation, followed by a post-treatment with UV, ozone and hydrogen peroxide. The removal of the contaminant with the waste sludge collected during the electrochemical treatment was also tested. The combined electrochemical and advanced oxidation treatment resulted in the complete removal of arsenic, phosphates, color, turbidity, suspended solids and ammonia, while the removal of other contaminants of interest was up to 96.7%. Comparable removal efficiencies were obtained by using waste sludge as a coagulant.

  6. Atomic Structure and Valence: Level II, Unit 10, Lesson 1; Chemical Bonding: Lesson 2; The Table of Elements: Lesson 3; Electrolysis: Lesson 4. Advanced General Education Program. A High School Self-Study Program.

    Science.gov (United States)

    Manpower Administration (DOL), Washington, DC. Job Corps.

    This self-study program for high-school level contains lessons on: Atomic Structure and Valence, Chemical Bonding, The Table of Elements, and Electrolysis. Each of the lessons concludes with a Mastery Test to be completed by the student. (DB)

  7. Stabilization/solidification of mercury-contaminated waste ash using calcium sodium phosphate (CNP) and magnesium potassium phosphate (MKP) processes.

    Science.gov (United States)

    Cho, Jae Han; Eom, Yujin; Lee, Tai Gyu

    2014-08-15

    This study examined the stabilization and solidification (S/S) of mercury (Hg)-contaminated waste ash generated from an industrial waste incinerator using chemically bonded phosphate ceramic (CBPC) technology. A magnesium potassium phosphate (MKP; MgKPO4 · 6H2O) ceramic, fabricated from MgO and KH2PO4, and a calcium sodium phosphate (CNP; CaNaPO4) ceramic, fabricated from CaO and Na2HPO4, were used as solidification binders in the CBPC process, and Na2S or FeS was added to each solidification binder to stabilize the Hg-contaminated waste ash. The S/S processes were conducted under various operating conditions (based on the solidification binder and stabilization reagent, stabilization reagent dosage, and waste loading ratio), and the performance characteristics of the S/S sample under each operating condition were compared, including the Hg leaching value and compressive strength. The Hg leaching value of untreated Hg-contaminated waste ash was 231.3 μg/L, whereas the S/S samples treated using the MKP and CNP processes exhibited Hg leaching values below the universal treatment standard (UTS) limit (25 μg/L). Although the compressive strengths of the S/S samples decreased as the sulfide dosage and waste loading ratio were increased, most of the S/S samples fabricated by the MKP and CNP processes exhibited good mechanical properties.

  8. Bond Issues.

    Science.gov (United States)

    Pollack, Rachel H.

    2000-01-01

    Notes trends toward increased borrowing by colleges and universities and offers guidelines for institutions that are considering issuing bonds to raise money for capital projects. Discussion covers advantages of using bond financing, how use of bonds impacts on traditional fund raising, other cautions and concerns, and some troubling aspects of…

  9. Three methods to measure RH bond energies

    Energy Technology Data Exchange (ETDEWEB)

    Berkowitz, J. [Argonne National Lab., IL (United States); Ellison, G.B. [Univ. of Colorado, Boulder, CO (United States). Dept. of Chemistry and Biochemistry; Gutman, D. [Catholic Univ. of America, Washington, DC (United States). Dept. of Chemistry

    1993-03-21

    In this paper the authors compare and contrast three powerful methods for experimentally measuring bond energies in polyatomic molecules. The methods are: radical kinetics; gas phase acidity cycles; and photoionization mass spectroscopy. The knowledge of the values of bond energies are a basic piece of information to a chemist. Chemical reactions involve the making and breaking of chemical bonds. It has been shown that comparable bonds in polyatomic molecules, compared to the same bonds in radicals, can be significantly different. These bond energies can be measured in terms of bond dissociation energies.

  10. Comparison of the effect of shear bond strength with silane and other three chemical presurface treatments of a glass fiber-reinforced post on adhesion with a resin-based luting agent: An in vitro study

    Directory of Open Access Journals (Sweden)

    Vaibhavi Ramkrishna Belwalkar

    2016-01-01

    Full Text Available Background: Loss of retention has been cited to be the most common cause of the failure of postretained restoration with irreversible consequences when materials with different compositions are in intimate contact at the post/adhesive interface. With this background, a study was conducted to improve the adhesion at the resin phase of fiber posts using silane and other chemical pretreatments. Materials and Methods: Hundred glass fiber-reinforced posts were tested with 4 different protocols (n = 25 using silane as a control (Group A and other three experimental groups, namely, Group B-20% potassium permanganate, Group C-4% hydrofluoric acid, and Group D-10% hydrogen peroxide were pretreated on the postsurface followed by silanization. These specimens were bonded with dual-polymerizing resin-based luting agent, which were then loaded at the crosshead speed of 1 mm/min to record the shear bond strength at the post/adhesive interface. The data were analyzed using one-way ANOVA test for multiple group comparisons and the post hoc Bonferroni test for pairwise comparisons (P < 0.05. Results: Group B showed more influence on the shear bond strength when compared to other protocols, respectively (P < 0.001. Conclusion: Alone silanization as a surface treatment did not improve the bond strength. Combination of chemical presurface treatments followed by silanization significantly enhanced the bond strength at the post/adhesive interface.

  11. Comparison of the effect of shear bond strength with silane and other three chemical presurface treatments of a glass fiber-reinforced post on adhesion with a resin-based luting agent: An in vitro study

    Science.gov (United States)

    Belwalkar, Vaibhavi Ramkrishna; Gade, Jaykumar; Mankar, Nikhil Purushottam

    2016-01-01

    Background: Loss of retention has been cited to be the most common cause of the failure of postretained restoration with irreversible consequences when materials with different compositions are in intimate contact at the post/adhesive interface. With this background, a study was conducted to improve the adhesion at the resin phase of fiber posts using silane and other chemical pretreatments. Materials and Methods: Hundred glass fiber-reinforced posts were tested with 4 different protocols (n = 25) using silane as a control (Group A) and other three experimental groups, namely, Group B-20% potassium permanganate, Group C-4% hydrofluoric acid, and Group D-10% hydrogen peroxide were pretreated on the postsurface followed by silanization. These specimens were bonded with dual-polymerizing resin-based luting agent, which were then loaded at the crosshead speed of 1 mm/min to record the shear bond strength at the post/adhesive interface. The data were analyzed using one-way ANOVA test for multiple group comparisons and the post hoc Bonferroni test for pairwise comparisons (P < 0.05). Results: Group B showed more influence on the shear bond strength when compared to other protocols, respectively (P < 0.001). Conclusion: Alone silanization as a surface treatment did not improve the bond strength. Combination of chemical presurface treatments followed by silanization significantly enhanced the bond strength at the post/adhesive interface. PMID:27307666

  12. Geometrical criteria versus quantum chemical criteria for assessment of intramolecular hydrogen bond (IMHB) interaction: A computational comparison into the effect of chlorine substitution on IMHB of salicylic acid in its lowest energy ground state conformer

    Energy Technology Data Exchange (ETDEWEB)

    Paul, Bijan Kumar [Department of Chemistry, University of Calcutta, 92 A.P.C. Road, Calcutta 700009 (India); Guchhait, Nikhil, E-mail: nikhil.guchhait@rediffmail.com [Department of Chemistry, University of Calcutta, 92 A.P.C. Road, Calcutta 700009 (India)

    2013-02-01

    Highlights: ► Intramolecular hydrogen bonding (IMHB) in salicylic acid and its chloro derivatives. ► A complex effect of +R and −I effect of chlorine substituents on IMHB energy. ► Interplay between IMHB energy and aromaticity. ► Directional nature of IMHB from quantum chemical assessment. ► Quantum chemical treatment vs. geometrical criteria to assess weak interaction. - Abstract: Density functional theory based computational study has been performed to characterize intramolecular hydrogen bonding (IMHB) interaction in a series of salicylic acid derivatives varying in chlorine substitution on the benzene ring. The molecular systems studied are salicylic acid, 5-chlorosalicylic acid, 3,5-dichlorosalicylic acid and 3,5,6-tricholorosalicylic acid. Major emphasis is rendered on the analysis of IMHB interaction by calculation of electron density ρ(r) and Laplacian ∇{sup 2}ρ(r) at the bond critical point using atoms-in-molecule theory. Topological features, energy densities based on ρ(r) through perturbing the intramolecular H-bond distances suggest that at equilibrium geometry the IMHB interaction develops certain characteristics typical of covalent interaction. The interplay between aromaticity and resonance-assisted hydrogen bonding (RAHB) is discussed using both geometrical and magnetic criteria as the descriptors of aromaticity. The optimized geometry features, molecular electrostatic potential map analysis are also found to produce a consensus view in relation with the formation of RAHB in these systems.

  13. Advanced Fabrication of Chemically Bonded Graphene/TiO2 Continuous Fibers with Enhanced Broadband Photocatalytic Properties and Involved Mechanisms Exploration

    Science.gov (United States)

    Zhang, Qingzhe; Bao, Nan; Wang, Xinqiang; Hu, Xinde; Miao, Xinhan; Chaker, Mohamed; Ma, Dongling

    2016-12-01

    In this article, a novel route for the synthesis of graphene/TiO2 continuous fibers (GTF) using force-spinning combined with water vapor annealing method is reported for the first time. The morphology, structure and optical properties of the composite were fully characterized. With a single step of heat treatment process using steam at ambient conditions, we were able to initiate a series of chemical reactions, such as reduction of graphene oxide (GO), crystallization of TiO2, formation of C-Ti bond, and introduction of oxygen vacancies into TiO2. The incorporation of graphene in TiO2 fibers facilitated bandgap narrowing and improved photo-induced charge separation in the photocatalyst. As a result of synergistic effects, TiO2 fibers-2 wt% graphene (2%GTF) showed the highest photocatalytic activities in the degradation of X-3B under UV irradiation, superior to the benchmark photocatalyst P25. Under visible light irradiation, the same catalyst was about 4 times more efficient compared to pure TiO2 fibers (PTF). A detailed study of involved active species (in particular, ·, h+ and ·OH) unraveled the mechanism regarding photocatalysis.

  14. Effect of surface pretreatment on interfacial chemical bonding states of atomic layer deposited ZrO{sub 2} on AlGaN

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Gang; Arulkumaran, Subramaniam; Ng, Geok Ing; Li, Yang; Ang, Kian Siong [School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore); Wang, Hong, E-mail: ewanghong@ntu.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore and CINTRA CNRS/NTU/Thales, UMI 3288, 50 Nanyang Drive, Singapore 637553 (Singapore); Ng, Serene Lay Geok; Ji, Rong [Data Storage Institute, Agency for Science Technology and Research (A-STAR), 5 Engineering Drive 1, Singapore 117608 (Singapore); Liu, Zhi Hong [Singapore-MIT Alliance for Research and Technology, 1 CREATE Way, Singapore 138602 (Singapore)

    2015-09-15

    Atomic layer deposition (ALD) of ZrO{sub 2} on native oxide covered (untreated) and buffered oxide etchant (BOE) treated AlGaN surface was analyzed by utilizing x-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy. Evidenced by Ga–O and Al–O chemical bonds by XPS, parasitic oxidation during deposition is largely enhanced on BOE treated AlGaN surface. Due to the high reactivity of Al atoms, more prominent oxidation of Al atoms is observed, which leads to thicker interfacial layer formed on BOE treated surface. The results suggest that native oxide on AlGaN surface may serve as a protecting layer to inhibit the surface from further parasitic oxidation during ALD. The findings provide important process guidelines for the use of ALD ZrO{sub 2} and its pre-ALD surface treatments for high-k AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors and other related device applications.

  15. Silica chemically bonded N-propyl kriptofix 21 and 22 with immobilized palladium nanoparticles for solid phase extraction and preconcentration of some metal ions.

    Science.gov (United States)

    Ghaedi, Mehrorang; Niknam, Khodabakhsh; Zamani, Saeed; Larki, Habib Abasi; Roosta, Mostafa; Soylak, Mustafa

    2013-08-01

    Silica gel chemically bonded N-propyl kriptofix 21 (SBNPK 21) and N-propyl kriptofix 22 (SBNPK 22) and subsequently immobilized with palladium nanoparticles (PNP-SBNPK 21 and PNP-SBNPK 22) to produce two new complexing lipophilic materials. Then these novel sorbents were applied for the enrichment of some metal ions and their subsequent determination by flame atomic absorption spectroscopy (FAAS). The influences of the variables including pH, amount of solid phase, sample flow rate, eluent conditions and sample volume on the metal ion recoveries were investigated. The detection limit of proposed method was in the interval 2.1-2.3 and 1.7-2.8 ng mL(-1) for PNP-SBNPK 21 and PNP-SBNPK 22 respectively, while the preconcentration factor was 80 for two sorbents. The relative standard deviations of recoveries were between 1.23-1.31 and 1.28-1.49 for PNP-SBNPK 21 and PNP-SBNPK 22 respectively. The method has high sorption-preconcentration efficiency even in the presence of various interfering ions. Due to the reasonable selectivity of proposed method, the relative standard deviation of recoveries of all understudied metal ions in some complicated matrices was less than 3.0%.

  16. Experimental charge density and neutron structural study of cis-HMn(CO){sub 4}PPh{sub 3}: Comprehensive analysis of chemical bonding and evidence for a C-H{hor_ellipsis}H-Mn hydrogen bond

    Energy Technology Data Exchange (ETDEWEB)

    Abramov, Y.A.; Brammer, L. [Univ. of Missouri, St. Louis, MO (United States). Dept. of Chemistry; Klooster, W.T.; Bullock, R.M. [Brookhaven National Lab., Upton, NY (United States). Chemistry Dept.

    1998-11-30

    The structure and bonding in cis-HMn(CO){sub 4}PPh{sub 3} have been studied by low-temperature neutron and high-resolution X-ray diffraction, the latter study using a charge-coupled device (CCD) area detector. A charge density analysis, including the deformation density, a full topological analysis of {minus}{del}{sup 2}{rho}, has been conducted. The electrostatic component of the H{sup {delta}+}{hor_ellipsis}H{sup {delta}{minus}} interaction energy is calculated to be 5.7 kcal/mol from the experimental data. This electrostatic evidence coupled with the geometry C-H{hor_ellipsis}H 129.0(2){degree} and H{hor_ellipsis}H-Mn 126.5(1){degree} and the identification of an H{hor_ellipsis}H bond path in the charge density distribution strongly supports the characterization of this interaction as an intramolecular C-H{hor_ellipsis}H-Mn hydrogen bond. Both the deformation density and the topological study clearly illustrate the {sigma}-donor nature of both the H-Mn and Ph{sub 3}P-Mn interactions and the {sigma}-donor/{pi}-acceptor nature of the manganese-carbonyl bonds. The topological study further confirms the decrease in C-O bond order upon coordination to the metal and demonstrates for the first time by this method that the metal-ligand bonds, although showing characteristics of a closed-shell interaction, do have a significant dative covalent component to the bond. The latter is reinforced by a study of the derived Mn d-orbital populations, in which populations of the d{sub z{sup 2}} and d{sub x{sup 2}{minus}y{sup 2}} orbitals are significantly higher than would be predicted by a simple crystal field theory model of metal-ligand bonding.

  17. Interrelationships among biological activity, disulfide bonds, secondary structure, and metal ion binding for a chemically synthesized 34-amino-acid peptide derived from alpha-fetoprotein.

    Science.gov (United States)

    MacColl, R; Eisele, L E; Stack, R F; Hauer, C; Vakharia, D D; Benno, A; Kelly, W C; Mizejewski, G J

    2001-10-01

    A 34-amino-acid peptide has been chemically synthesized based on a sequence from human alpha-fetoprotein. The purified peptide is active in anti-growth assays when freshly prepared in pH 7.4 buffer at 0.20 g/l, but this peptide slowly becomes inactive. This functional change is proven by mass spectrometry to be triggered by the formation of an intrapeptide disulfide bond between the two cysteine residues on the peptide. Interpeptide cross-linking does not occur. The active and inactive forms of the peptide have almost identical secondary structures as shown by circular dichroism (CD). Zinc ions bind to the active peptide and completely prevents formation of the inactive form. Cobalt(II) ions also bind to the peptide, and the UV-Vis absorption spectrum of the cobalt-peptide complex shows that: (1) a near-UV sulfur-to-metal-ion charge-transfer band had a molar extinction coefficient consistent with two thiolate bonds to Co(II); (2) the lowest-energy visible d-d transition maximum at 659 nm, also, demonstrated that the two cysteine residues are ligands for the metal ion; (3) the d-d molar extinction coefficient showed that the metal ion-ligand complex was in a distorted tetrahedral symmetry. The peptide has two cysteines, and it is speculated that the other two metal ion ligands might be the two histidines. The Zn(II)- and Co(II)-peptide complexes had similar peptide conformations as indicated by their ultraviolet CD spectra, which differed very slightly from that of the free peptide. Surprisingly, the cobalt ions acted in the reverse of the zinc ions in that, instead of stabilizing anti-growth form of the peptide, they catalyzed its loss. Metal ion control of peptide function is a saliently interesting concept. Calcium ions, in the conditions studied, apparently do not bind to the peptide. Trifluoroethanol and temperature (60 degrees C) affected the secondary structure of the peptide, and the peptide was found capable of assuming various conformations in solution

  18. Physical and chemical properties of pyropheophorbide-a methyl ester in ethanol, phosphate buffer and aqueous dispersion of small unilamellar dimyristoyl-L-alpha-phosphatidylcholine vesicles.

    Science.gov (United States)

    Delanaye, Lisiane; Bahri, Mohamed Ali; Tfibel, Francis; Fontaine-Aupart, Marie-Pierre; Mouithys-Mickalad, Ange; Heine, Bélinda; Piette, Jacques; Hoebeke, Maryse

    2006-03-01

    The aggregation process of pyropheophorbide-a methyl ester (PPME), a second-generation photosensitizer, was investigated in various solvents. Absorption and fluorescence spectra showed that the photosensitizer was under a monomeric form in ethanol as well as in dimyristoyl-L-alpha-phosphatidylcholine liposomes while it was strongly aggregated in phosphate buffer. A quantitative determination of reactive oxygen species production by PPME in these solvents has been undertaken by electron spin resonance associated with spin trapping technique and absorption spectroscopy. In phosphate buffer, both electron spin resonance and absorption measurements led to the conclusion that singlet oxygen production was not detectable while hydroxyl radical production was very weak. In liposomes and ethanol, singlet oxygen and hydroxyl radical production increased highly; the singlet oxygen quantum yield was determined to be 0.2 in ethanol and 0.13 in liposomes. The hydroxyl radical production origin was also investigated. Singlet oxygen was formed from PPME triplet state deactivation in the presence of oxygen. Indeed, the triplet state formation quantum yield of PPME was found to be about 0.23 in ethanol, 0.15 in liposomes (too small to be measured in PBS).

  19. Localization of double bonds in wax esters by high-performance liquid chromatography/atmospheric pressure chemical ionization mass spectrometry utilizing the fragmentation of acetonitrile-related adducts.

    Science.gov (United States)

    Vrkoslav, Vladimír; Háková, Martina; Pecková, Karolina; Urbanová, Klára; Cvačka, Josef

    2011-04-15

    Unsaturated wax esters (WEs) provided molecular adducts with C(3)H(5)N ([M + 55](+•)) in APCI sources in the presence of acetonitrile. CID MS/MS of [M + 55](+•) yielded fragments allowing the localization of double bond(s) in the hydrocarbon chains of the WEs. These fragments were formed by a cleavage on each side of the double bond. In methylene-interrupted polyunsaturated WEs, diagnostic fragments related to each double bond were detected; the most abundant were those corresponding to the cleavage of the C-C bond next to the first and the last double bond. To differentiate between those fragments differing in their structure or origin, a simple nomenclature based on α and ω ions has been introduced. Fragmentation of the α-type ions (fragments containing an ester bond) provided information on the occurrence of a double bond in the acid or alcohol part of the WEs. While no significant differences between the spectra of the WEs differing by cis/trans isomerism were found, the isomers were separated chromatographically. A data-dependent HPLC/APCI-MS(2) method for the comprehensive characterization of WEs in their complex mixtures has been developed and applied to natural mixtures of WEs isolated from jojoba oil and beeswax. More than 50 WE molecular species were completely identified, including the information on the acid and alcohol chain length and the position of the double bonds.

  20. CHEMICALS

    CERN Multimedia

    Medical Service

    2002-01-01

    It is reminded that all persons who use chemicals must inform CERN's Chemistry Service (TIS-GS-GC) and the CERN Medical Service (TIS-ME). Information concerning their toxicity or other hazards as well as the necessary individual and collective protection measures will be provided by these two services. Users must be in possession of a material safety data sheet (MSDS) for each chemical used. These can be obtained by one of several means : the manufacturer of the chemical (legally obliged to supply an MSDS for each chemical delivered) ; CERN's Chemistry Service of the General Safety Group of TIS ; for chemicals and gases available in the CERN Stores the MSDS has been made available via EDH either in pdf format or else via a link to the supplier's web site. Training courses in chemical safety are available for registration via HR-TD. CERN Medical Service : TIS-ME :73186 or service.medical@cern.ch Chemistry Service : TIS-GS-GC : 78546

  1. Ultrasonic and Thermal Properties of Borate and Phosphate Glasses Containing Bismuth and Lead

    Science.gov (United States)

    Aziz, Sidek Hj. Abd.; Ahmad, Hamezan; Wahab, Zaidan A.; Sulaiman, Zainal Abidin; Talib, Zainal Abidin; Shaari, A. Halim; Senin, H. B.

    2007-05-01

    Systematic series of (B2O3,P2O5)-Bi2O3-PbO glasses have been successfully prepared by using the rapid quenching technique in which each oxide content changes for every series on the basis of its weight percentage. Their amorphous natures were confirmed earlier by the x-ray diffraction technique. The experimental results show that the density of both glasses, determined by using the Archimedes principle, increases with the glass modifier content. This is due to the replacement of Bi2O3 and PbO in the borate and phosphate glassy networks. The molar volume for borate glass increases with the addition of bismuth and lead oxides, but a reverse trend occurs for the phosphate glass. The longitudinal and shear ultrasound velocities, determined by the MBS 8000 system, of both lead bismuth borate and phosphate glasses show a decreasing trend as more PbO and Bi2O3 are added to the glass system. The increase in PbO/Bi2O3 content was probably related to the progressive increase in the concentration of non-bridging oxygen (NBOs). Thermal studies of the glass, using the Labsys DTA-Setaram machine, show that the value of the glass transition temperature (Tg) is closely related to the chemical bond in the system. In lead bismuth borate glasses, the addition of more Pb2+ and Bi3+ results in a more dominant ionic bond character in the system and hence decreases Tg of the sample. However, in lead bismuth phosphate glasses, the addition of Pb2+ and Bi3+ not only failed to weaken the covalent character in P-O-P bonds, but strengthened it further, leading to an increment in the values of Tg.

  2. Integrated mined-area reclamation and land use planning. Volume 3B. A case study of surface mining and reclamation planning: international minerals and chemical corporation, phosphate operations, Polk County, Florida. [Land reclamation and use planning for phosphate operations in Polk County, Florida

    Energy Technology Data Exchange (ETDEWEB)

    LaFevers, J R; Brown, L A; Fountain, R C

    1977-02-01

    The reports in this series are designed primarily to familiarize professional land use and resource planners with the range of possibilities and effective procedures for achieving integrated mining, reclamation, and land use planning. These reports are based on a research program which included an extensive literature review, the compilation and analysis of case study data, and close coordination and interaction with related government programs. In Volume 3, A Guide to Mined Area Reclamation Technology for Reclamation and Land Use Planners, the method used to reclaim land in each of several mineral industries are discussed in relation to the physical and cultural constraints that must be considered in planning a reclamation program. Much of the information for this document was obtained from case studies conducted in several mining districts. Volume 3B presents data from a case study of surface mining and reclamation planning, International Minerals and Chemical Corporation, Phosphate Operations, Polk County, Florida.

  3. Effective removal of methyl blue by fine-structured strontium and barium phosphate nanorods

    Science.gov (United States)

    Zhang, Fan; Song, Weijie; Lan, Jing

    2015-01-01

    In this work, the composite of strontium phosphate and barium phosphate (called SBP) nanorods have been synthesized, characterized and studied for removal of methyl blue (MB). The effects of pH, temperature, contact time, initial dye concentration on removal of MB were studied in detail. Results suggest that pH and temperature were not critical limiting factors for the removal of MB. Reaching equilibrium was very rapid (within 10 min) and the high adsorption capacity of MB by SBP nanorods was 1691.8 mg/g at initial dye concentration of 2000 mg/L. The adsorption process obeyed the pseudo-second-order kinetics model and Langmuir isotherm model. Importantly, the mechanism contributed to the MB removal was proposed to be the ionic interaction and hydrogen bonds for low dye concentration, chemical precipitation for high dye concentration. It is predicted that the SBP nanorods being an effective adsorbent for elimination of MB from colored aqueous solutions.

  4. Comparative anti-inflammatory activities of curcumin and tetrahydrocurcumin based on the phenolic O-H bond dissociation enthalpy, ionization potential and quantum chemical descriptor.

    Science.gov (United States)

    Murakami, Yukio; Ishii, Hiroaki; Takada, Naoki; Tanaka, Shoji; Machino, Mamoru; Ito, Shigeru; Fujisawa, Seiichiro

    2008-01-01

    Curcumin and its reduced derivative tetrahydrocurcumin have been shown to exhibit chemopreventive activity. Cyclooxygenase-2 (COX-2) inhibition in lipopolysaccharide (LPS)- or Porphyromonas gingivalis fimbria-stimulated RAW 264.7 cells was investigated using Northern blot analysis. The fimbria-stimulated expression of the COX-2 gene was inhibited by curcumin but not by tetrahydrocurcumin. LPS-stimulated COX-2 gene expression was completely inhibited by curcumin, but an increase in the concentration of tetrahydrocurcumin did not cause complete inhibition of COX-2 expression. The inhibitory effect of curcumin on nuclear factor kappa B (NF-kappaB) activation in the cells was clearly observed, but that of tetrahydrocurcumin was incomplete even at a concentration of 20 microM. To explain the difference in effect between the two compounds, analysis of the frontier orbital was performed using ab initio 6-31G* wave function. The calculated chemical hardness (eta) for curcumin was clearly smaller, whereas its electronegativity (chi) and electrophilicity (omega) were clearly greater than the corresponding values for the curcumin-related compounds tetrahydrocurcumin, isoeugenol and eugenol. This suggested that the anti-inflammatory activities of curcumin may be related to eta-, chi- and/or omega-controlled enzymes. In addition, the bond dissociation enthalpy (BDE) of the phenolic OH was calculated using the density function theory (DFT)/B3LY. The total BDE values of curcumin and tetrahydrocurcumin were almost identical, but the BDE of one-electron oxidation and ionization potential (IP) for curcumin were lower than those for tetrahydrocurcumin, suggesting the highly pro-oxidative activity of curcumin. Curcumin has both oxidant and antioxidant properties. A causal link between the anti-inflammatory activities and molecular properties of phenolic antioxidants is suggested.

  5. Silica chemically bonded N-propyl kriptofix 21 and 22 with immobilized palladium nanoparticles for solid phase extraction and preconcentration of some metal ions

    Energy Technology Data Exchange (ETDEWEB)

    Ghaedi, Mehrorang, E-mail: m_ghaedi@mail.yu.ac.ir [Chemistry Department, Yasouj University, Yasouj, 75914-353 (Iran, Islamic Republic of); Niknam, Khodabakhsh, E-mail: niknam@pgu.ac.ir [Chemistry Department, Faculty of Sciences, Persian Gulf University, Bushehr, 75169 (Iran, Islamic Republic of); Zamani, Saeed; Abasi Larki, Habib [Chemistry Department, Islamic Azad University, Omidiyeh Branch, Omidiyeh (Iran, Islamic Republic of); Roosta, Mostafa [Chemistry Department, Yasouj University, Yasouj, 75914-353 (Iran, Islamic Republic of); Soylak, Mustafa [Chemistry Department, University of Erciyes, 38039 Kayseri (Turkey)

    2013-08-01

    Silica gel chemically bonded N-propyl kriptofix 21 (SBNPK 21) and N-propyl kriptofix 22 (SBNPK 22) and subsequently immobilized with palladium nanoparticles (PNP-SBNPK 21 and PNP-SBNPK 22) to produce two new complexing lipophilic materials. Then these novel sorbents were applied for the enrichment of some metal ions and their subsequent determination by flame atomic absorption spectroscopy (FAAS). The influences of the variables including pH, amount of solid phase, sample flow rate, eluent conditions and sample volume on the metal ion recoveries were investigated. The detection limit of proposed method was in the interval 2.1–2.3 and 1.7–2.8 ng mL{sup −1} for PNP-SBNPK 21 and PNP-SBNPK 22 respectively, while the preconcentration factor was 80 for two sorbents. The relative standard deviations of recoveries were between 1.23–1.31 and 1.28–1.49 for PNP-SBNPK 21 and PNP-SBNPK 22 respectively. The method has high sorption-preconcentration efficiency even in the presence of various interfering ions. Due to the reasonable selectivity of proposed method, the relative standard deviation of recoveries of all understudied metal ions in some complicated matrices was less than 3.0%. Highlights: • Highly selective sorbents for solid phase extraction were synthesized. • The method has been successfully applied for the determination of trace metals ions. • Excellent properties of the sorbent have been illustrated in detail.

  6. Parental Bonding

    Directory of Open Access Journals (Sweden)

    T. Paul de Cock

    2014-08-01

    Full Text Available Estimating the early parent–child bonding relationship can be valuable in research and practice. Retrospective dimensional measures of parental bonding provide a means for assessing the experience of the early parent–child relationship. However, combinations of dimensional scores may provide information that is not readily captured with a dimensional approach. This study was designed to assess the presence of homogeneous groups in the population with similar profiles on parental bonding dimensions. Using a short version of the Parental Bonding Instrument (PBI, three parental bonding dimensions (care, authoritarianism, and overprotection were used to assess the presence of unobserved groups in the population using latent profile analysis. The class solutions were regressed on 23 covariates (demographics, parental psychopathology, loss events, and childhood contextual factors to assess the validity of the class solution. The results indicated four distinct profiles of parental bonding for fathers as well as mothers. Parental bonding profiles were significantly associated with a broad range of covariates. This person-centered approach to parental bonding has broad utility in future research which takes into account the effect of parent–child bonding, especially with regard to “affectionless control” style parenting.

  7. Effect of Interface Bond Type on the Structure of InAs/GaSb Superlattices Grown by Metalorganic Chemical Vapor Deposition

    Institute of Scientific and Technical Information of China (English)

    LI Li-Gong; LIUShu-Man; LUO Shuai; YANG Tao; WANG Li-Jun; LIUFeng-Qi; YE Xiao-Ling; XU Bo; WANG Zhan-Guo

    2011-01-01

    InAs/GaSb type-II superlattices were grown on (100) GaSb substrates by meta.lorga.nic chemical vapor deposition. Raman scattering spectroscopy reveals that it is possible to grow superlattices with almost pure GaAs-like and mixed-like (plane of mixed As and Sb atoms that connect the GaSb and lnAs layers) interfaces. Introducing the InSb-like interface results in nanopipes and As contamination of the GaSb layers. X-ray diffraction and atomic force microscopy demonstrate that the superlattices with a mixed-like interface have better morphology and crystalline quality.%InAs/GaSb type-Ⅱ superlattices were grown on (100) GaSb substrates by metalorganic chemical vapor deposition.Raman scattering spectroscopy reveals that it is possible to grow superlattices with almost pure GaAs-like and mixed-like (plane of mixed As and Sb atoms that connect the GaSb and InAs layers) interfaces.Introducing the InSb-like interface results in nanopipes and As contamination of the GaSb layers.X-ray diffraction and atomic force microscopy demonstrate that the superlattices with a mixed-like interface have better morphology and crystalline quality.InAs/GaSb type-Ⅱ superlattices (SLs) have been shown to be a promising alternative to the existing HgCdTe and quantum well infrared detectors.[1,2]This material system can be tailored over a wide range of infrared wavelength from 3 to more than 30 μm by changing the thicknesses of the InAs and GaSb layers.Using the same technique,the Auger recombination rate can be significantly reduced in InAs/GaSb SLs,which is especially important for realizing high-performance infrared detectors at room temperature.[3,4] Furthermore,due to the large electron effective mass of the SL structures,the bandto-band tunneling current is intrinsically small compared to that of HgCdTe.[5] Since both the anion and the cation change across the interface (IF) of the InAs/GaSb SL,two types of interfaces are possible,InSb-like and GaAs-like.It has been shown that the

  8. A Vision of Interdisciplinary Education: Students' Reasoning about "High-Energy Bonds" and ATP

    CERN Document Server

    Dreyfus, Benjamin W; Turpen, Chandra; Gouvea, Julia; Redish, Edward F

    2014-01-01

    As interdisciplinary courses are developed, instructors and researchers have to grapple with questions of how students should make connections across disciplines. We explore the issue of interdisciplinary reconciliation (IDR): how students reconcile seemingly contradictory ideas from different disciplines. While IDR has elements in common with other frameworks for the reconciliation of ideas across contexts, it differs in that each disciplinary idea is considered canonically correct within its own discipline. The setting for the research is an introductory physics course for biology majors that seeks to build greater interdisciplinary coherence and therefore includes biologically relevant topics such as ATP and chemical bond energy. In our case-study data, students grapple with the apparent contradiction between the energy released when the phosphate bond in ATP is broken and the idea that an energy input is required to break a bond. We see students justifying context-dependent modeling choices, showing nuanc...

  9. Tracing the Fingerprint of Chemical Bonds within the Electron Densities of Hydrocarbons: A Comparative Analysis of the Optimized and the Promolecule Densities.

    Science.gov (United States)

    Keyvani, Zahra Alimohammadi; Shahbazian, Shant; Zahedi, Mansour

    2016-10-18

    The equivalence of the molecular graphs emerging from the comparative analysis of the optimized and the promolecule electron densities in two hundred and twenty five unsubstituted hydrocarbons was recently demonstrated [Keyvani et al. Chem. Eur. J. 2016, 22, 5003]. Thus, the molecular graph of an optimized molecular electron density is not shaped by the formation of the C-H and C-C bonds. In the present study, to trace the fingerprint of the C-H and C-C bonds in the electron densities of the same set of hydrocarbons, the amount of electron density and its Laplacian at the (3, -1) critical points associated with these bonds are derived from both optimized and promolecule densities, and compared in a newly proposed comparative analysis. The analysis not only conforms to the qualitative picture of the electron density build up between two atoms upon formation of a bond in between, but also quantifies the resulting accumulation of the electron density at the (3, -1) critical points. The comparative analysis also reveals a unified mode of density accumulation in the case of 2318 studied C-H bonds, but various modes of density accumulation are observed in the case of 1509 studied C-C bonds and they are classified into four groups. The four emerging groups do not always conform to the traditional classification based on the bond orders. Furthermore, four C-C bonds described as exotic bonds in previous studies, for example the inverted C-C bond in 1,1,1-propellane, are naturally distinguished from the analysis.

  10. How do halogen bonds (S-O⋯I, N-O⋯I and C-O⋯I) and halogen-halogen contacts (C-I⋯I-C, C-F⋯F-C) subsist in crystal structures? A quantum chemical insight.

    Science.gov (United States)

    Pandiyan, B Vijaya; Deepa, P; Kolandaivel, P

    2017-01-01

    Thirteen X-ray crystal structures containing various non-covalent interactions such as halogen bonds, halogen-halogen contacts and hydrogen bonds (I⋯N, I⋯F, I⋯I, F⋯F, I⋯H and F⋯H) were considered and investigated using the DFT-D3 method (B97D/def2-QZVP). The interaction energies were calculated at MO62X/def2-QZVP and MP2/aug-cc-pvDZ level of theories. The higher interaction and dispersion energies (2nd crystal) of -9.58 kcal mol(-1) and -7.10 kcal mol(-1) observed for 1,4-di-iodotetrafluorobenzene bis [bis (2-phenylethyl) sulfoxide] structure indicates the most stable geometrical arrangement in the crystal packing. The electrostatic potential values calculated for all crystal structures have a positive σ-hole, which aids understanding of the nature of σ-hole bonds. The significance of the existence of halogen bonds in crystal packing environments was authenticated by replacing iodine atoms by bromine and chlorine atoms. Nucleus independent chemical shift analysis reported on the resonance contribution to the interaction energies of halogen bonds and halogen-halogen contacts. Hirshfeld surface analysis and topological analysis (atoms in molecules) were carried out to analyze the occurrence and strength of all non-covalent interactions. These analyses revealed that halogen bond interactions were more dominant than hydrogen bonding interactions in these crystal structures. Graphical Abstract Molecluar structure of 1,4-Di-iodotetrafluorobenzene bis(thianthrene 5-oxide) moelcule and its corresponding molecular electrostatic potential map for the view of σ-hole.

  11. Study on the covalence of Cu and chemical bonding in an inorganic fullerene-like molecule, [CuCl]20[Cp*FeP5]12[Cu-(CH3CN)2+Cl-]5, by a density functional approach

    Institute of Scientific and Technical Information of China (English)

    WANG Bingwu; XU Guangxian; CHEN Zhida

    2004-01-01

    The electronic structure and chemical bonding in a recently synthesized inorganic fullerene-like molecule, {[CuCl]20[Cp*FeP5]12 [Cu(CH3CN)+2Cl-]5}, has been studied by a density functional approach. Geometrical optimization of the three basic structural units of the molecule is performed with Amsterdam Density Functional Program. The results are in agreement with the experiment. Localized MO's obtained by Boys-Foster method give a clear picture of the chemical bonding in this molecule. The reason why CuCl can react with Cp*FeP5 in solvent CH3CN to form the fullerene-like molecule is explained in terms of the soft-hard Lewis acid base theory and a new concept of covalence.

  12. Electronic, optical properties and chemical bonding in six novel 1111-like chalcogenide fluorides AMChF (A=Sr, Ba; M=Cu, Ag; and Ch=S, Se, Te) from first principles calculations

    Science.gov (United States)

    Bannikov, V. V.; Shein, I. R.; Ivanovskii, A. L.

    2012-12-01

    Employing first-principles band structure calculations, we have examined the electronic, optical properties and the peculiarities of the chemical bonding for six newly synthesized layered quaternary 1111-like chalcogenide fluorides SrAgSF, SrAgSeF, SrAgTeF, BaAgSF, BaAgSeF, and SrCuTeF, which are discussed in comparison with some isostructural 1111-like chalcogenide oxides. We found that all of the studied phases AMChF (A=Sr, Ba; M=Cu, Ag; and Ch=S, Se, Te) are semiconductors for which the fitted “experimental” gaps lie in the interval from 2.23 eV (for SrAgSeF) to 3.07 eV (for SrCuTeF). The near-Fermi states of AMChF are formed exclusively by the valence orbitals of the atoms from the blocks (MCh); thus, these phases belong to the layered materials with “natural multiple quantum wells”. The bonding in these new AMChF phases is described as a high-anisotropic mixture of ionic and covalent contributions, where ionic M-Ch bonds together with covalent M-Ch and Ch-Ch bonds take place inside blocks (MCh), while inside blocks (AF) and between the adjacent blocks (MCh)/(AF) mainly ionic bonds emerge.

  13. Bonding in cementitious composites

    Energy Technology Data Exchange (ETDEWEB)

    Mindess, S. (British Columbia Univ., Vancouver, BC (Canada)) Shah, S.P. (Northwestern Univ., Evanston, IL (USA))

    1988-01-01

    These proceedings discuss the papers presented at the symposium on the subject of high performance cement composites. Some of the topics discussed were; calcium hydroxides treated ceramics microspheres and mechanical properties of high temperature light weight cements; microstructure and chemical variations of class F fly ash; microstructure and bond strength of cement and crack propagation as detected by laser holography and acoustic emission.

  14. Phosphate based oil well cements

    Science.gov (United States)

    Natarajan, Ramkumar

    The main application of the cement in an oil well is to stabilize the steel casing in the borehole and protect it from corrosion. The cement is pumped through the borehole and is pushed upwards through the annulus between the casing and the formation. The cement will be exposed to temperature and pressure gradients of the borehole. Modified Portland cement that is being used presently has several shortcomings for borehole sealant. The setting of the Portland cement in permafrost regions is poor because the water in it will freeze even before the cement sets and because of high porosity and calcium oxide, a major ingredient it gets easily affected by the down hole gases such as carbon dioxide. The concept of phosphate bonded cements was born out of considerable work at Argonne National Laboratory (ANL) on their use in stabilization of radioactive and hazardous wastes. Novel cements were synthesized by an acid base reaction between a metal oxide and acid phosphate solution. The major objective of this research is to develop phosphate based oil well cements. We have used thermodynamics along with solution chemistry principles to select calcined magnesium oxide as candidate metal oxide for temperatures up to 200°F (93.3°C) and alumina for temperatures greater than 200°F (93.3°C). Solution chemistry helped us in selecting mono potassium phosphate as the acid component for temperatures less than 200°F (93.3°C) and phosphoric acid solution greater than 200°F (93.3°C). These phosphate cements have performance superior to common Portland well cements in providing suitable thickening time, better mechanical and physical properties.

  15. Inverted-sandwich-type and open-lantern-type dinuclear transition metal complexes: theoretical study of chemical bonds by electronic stress tensor

    CERN Document Server

    Ichikawa, Kazuhide; Kurokawa, Yusaku I; Sakaki, Shigeyoshi; Tachibana, Akitomo

    2011-01-01

    We study the electronic structure of two types of transition metal complexes, the inverted-sandwich-type and open-lantern-type, by the electronic stress tensor. In particular, the bond order b_e measured by the energy density which is defined from the electronic stress tensor is studied and compared with the conventional MO based bond order. We also examine the patterns found in the largest eigenvalue of the stress tensor and corresponding eigenvector field, the "spindle structure" and "pseudo-spindle structure". As for the inverted-sandwich-type complex, our bond order b_e calculation shows that relative strength of the metal-benzene bond among V, Cr and Mn complexes is V > Cr > Mn which is consistent with the MO based bond order. As for the open-lantern-type complex, we find that our energy density based bond order can properly describe the relative strength of Cr--Cr and Mo--Mo bonds by the surface integration of the energy density over the "Lagrange surface" which can take into account the spatial extent ...

  16. Light weight phosphate cements

    Science.gov (United States)

    Wagh, Arun S.; Natarajan, Ramkumar,; Kahn, David

    2010-03-09

    A sealant having a specific gravity in the range of from about 0.7 to about 1.6 for heavy oil and/or coal bed methane fields is disclosed. The sealant has a binder including an oxide or hydroxide of Al or of Fe and a phosphoric acid solution. The binder may have MgO or an oxide of Fe and/or an acid phosphate. The binder is present from about 20 to about 50% by weight of the sealant with a lightweight additive present in the range of from about 1 to about 10% by weight of said sealant, a filler, and water sufficient to provide chemically bound water present in the range of from about 9 to about 36% by weight of the sealant when set. A porous ceramic is also disclosed.

  17. Computational Chemistry of Adhesive Bonds

    Science.gov (United States)

    Phillips, Donald H.

    1999-01-01

    This investigation is intended to determine the electrical mechanical, and chemical properties of adhesive bonds at the molecular level. The initial determinations will be followed by investigations of the effects of environmental effects on the chemistry and properties of the bond layer.

  18. An investigation of hydrogen-bonding effects on the nitrogen and hydrogen electric field gradient and chemical shielding tensors in the 9-methyladenine real crystalline structure: a density functional theory study.

    Science.gov (United States)

    Mirzaei, Mahmoud; Hadipour, Nasser L

    2006-04-13

    Hydrogen-bonding effects in the real crystalline structure of 9-methyladenine, 9-MA, were studied using calculated electric field gradient, EFG, and chemical shielding, CS, tensors for nitrogen and hydrogen nuclei via density functional theory. The calculations were carried out at the B3LYP and B3PW91 levels with the 6-311++G basis set via the Gaussian 98 package. Nuclear quadrupole coupling constants, C(Q), and asymmetry parameters, eta(Q), are reported for (14)N and (2)H. The chemical shielding anisotropy, Deltasigma, and chemical shielding isotropy, sigma(iso), are also reported for (15)N and (1)H. The difference between the calculated parameters of the monomer and heptameric layer-like cluster 9-MA shows how much H-bonding interactions affect the EFG and CS tensors of each nucleus. This result indicates that N(10) (imino nitrogen) has a major role in H-bonding interactions, whereas that of N(9) is negligible. There is good agreement between the present calculated parameters and reported experimental data. Although some discrepancies were observed, this could be attributed to the different conditions which were applied for calculation and the experiments.

  19. Phosphate homeostasis and disorders.

    Science.gov (United States)

    Manghat, P; Sodi, R; Swaminathan, R

    2014-11-01

    Recent studies of inherited disorders of phosphate metabolism have shed new light on the understanding of phosphate metabolism. Phosphate has important functions in the body and several mechanisms have evolved to regulate phosphate balance including vitamin D, parathyroid hormone and phosphatonins such as fibroblast growth factor-23 (FGF23). Disorders of phosphate homeostasis leading to hypo- and hyperphosphataemia are common and have clinical and biochemical consequences. Notably, recent studies have linked hyperphosphataemia with an increased risk of cardiovascular disease. This review outlines the recent advances in the understanding of phosphate homeostasis and describes the causes, investigation and management of hypo- and hyperphosphataemia.

  20. Benchmark quantum-chemical calculations on a complete set of rotameric families of the DNA sugar-phosphate backbone and their comparison with modern density functional theory.

    Science.gov (United States)

    Mládek, Arnošt; Krepl, Miroslav; Svozil, Daniel; Cech, Petr; Otyepka, Michal; Banáš, Pavel; Zgarbová, Marie; Jurečka, Petr; Sponer, Jiří

    2013-05-21

    The DNA sugar-phosphate backbone has a substantial influence on the DNA structural dynamics. Structural biology and bioinformatics studies revealed that the DNA backbone in experimental structures samples a wide range of distinct conformational substates, known as rotameric DNA backbone conformational families. Their correct description is essential for methods used to model nucleic acids and is known to be the Achilles heel of force field computations. In this study we report the benchmark database of MP2 calculations extrapolated to the complete basis set of atomic orbitals with aug-cc-pVTZ and aug-cc-pVQZ basis sets, MP2(T,Q), augmented by ΔCCSD(T)/aug-cc-pVDZ corrections. The calculations are performed in the gas phase as well as using a COSMO solvent model. This study includes a complete set of 18 established and biochemically most important families of DNA backbone conformations and several other salient conformations that we identified in experimental structures. We utilize an electronically sufficiently complete DNA sugar-phosphate-sugar (SPS) backbone model system truncated to prevent undesired intramolecular interactions. The calculations are then compared with other QM methods. The BLYP and TPSS functionals supplemented with Grimme's D3(BJ) dispersion term provide the best tradeoff between computational demands and accuracy and can be recommended for preliminary conformational searches as well as calculations on large model systems. Among the tested methods, the best agreement with the benchmark database has been obtained for the double-hybrid DSD-BLYP functional in combination with a quadruple-ζ basis set, which is, however, computationally very demanding. The new hybrid density functionals PW6B95-D3 and MPW1B95-D3 yield outstanding results and even slightly outperform the computationally more demanding PWPB95 double-hybrid functional. B3LYP-D3 is somewhat less accurate compared to the other hybrids. Extrapolated MP2(D,T) calculations are not as

  1. LAMMPS Framework for Directional Dynamic Bonding

    DEFF Research Database (Denmark)

    2012-01-01

    and bond types. When breaking bonds, all angular and dihedral interactions involving broken bonds are removed. The framework allows chemical reactions to be modeled, and use it to simulate a simplistic, coarse-grained DNA model. The resulting DNA dynamics illustrates the power of the present framework.......We have extended the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) to support directional bonds and dynamic bonding. The framework supports stochastic formation of new bonds, breakage of existing bonds, and conversion between bond types. Bond formation can be controlled...... to limit the maximal functionality of a bead with respect to various bond types. Concomitant with the bond dynamics, angular and dihedral interactions are dynamically introduced between newly connected triplets and quartets of beads, where the interaction type is determined from the local pattern of bead...

  2. New chemical approach to obtain dense layer phosphate-based ionic conductor coating on negative electrode material surface: Synthesis way, outgassing and improvement of C-rate capability

    Science.gov (United States)

    Fleutot, Benoit; Davoisne, Carine; Gachot, Grégory; Cavalaglio, Sébastien; Grugeon, Sylvie; Viallet, Virginie

    2017-04-01

    Li4Ti5O12 (LTO) based batteries have severe gassing behavior during charge/discharge and storage process, due to interfacial reactions between active material and electrolyte solution. In the same time, the electronic and ionic conductivity of pristine LTO is very poor and induces the use of nanoparticles which increase the outgassing phenomena. The coating of LTO particles could be a solution. For this the LTO spinel particles are modified with ionic conductor Li3PO4 coating using a spray-drying method. For the first time a homogeneous thin dense layer phosphate based conductor is obtained without nanoparticles, as a thin film material. It is so possible to study the influence of ionic conductor deposited on the negative electrode material on performances by the controlled layer thickness. This coating was characterized by XRD, SEM, XPS and TEM. The electrochemical performance of Li3PO4 coated Li4Ti5O12 is improved at high C-rate by the surface modification (improvement of 30 mAh g-1 at 5 C-rate compared to pristine LTO for 5 nm of coating), inducing by a modification of surface energy. An optimum coating thickness was studied. This type of coating allows a significant decrease of outgassing phenomena due the conformal coating and opens the way to a great number of studies and new technologies.

  3. Glucose-6-phosphate dehydrogenase

    Science.gov (United States)

    ... medlineplus.gov/ency/article/003671.htm Glucose-6-phosphate dehydrogenase test To use the sharing features on this page, please enable JavaScript. Glucose-6-phosphate dehydrogenase (G6PD) is a protein that helps red ...

  4. Chloroquine Phosphate Oral

    Science.gov (United States)

    Chloroquine phosphate is in a class of drugs called antimalarials and amebicides. It is used to prevent and treat ... Chloroquine phosphate comes as a tablet to take by mouth. For prevention of malaria in adults, one dose is ...

  5. Influence of zinc and magnesium dopping on the physical and chemical properties of tricalcium phosphate powders; Influenciancia da dopagem de zinco e magnesio nas propriedades fisico-quimicas em pos de fosfato tricalcio

    Energy Technology Data Exchange (ETDEWEB)

    Machado, C.A.V.A.; Marchi, J., E-mail: carlos.machado.ufabc@gmail.com, E-mail: marchi.juliana@hotmail.com [Universidade Federal do ABC (CCNH/UFABC), Santo Andre, SP (Brazil). Centro de Ciencias Naturais e Humanas; Ussui, V.; Bressiani, A.H.A. [Instituto de Pesquisas Energeticas e Nucleares (CCTM/IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Ciencia e Tecnologia de Materiais

    2011-07-01

    Tricalcium phosphate (Ca{sub 3} (PO{sub 4}) {sub 2} - TCP) is a resorbable ceramic material has phases β-TCP and α-TCP. The β-TCP phase has a suitable solubility rate in order to maintain the bone cells structure, while α-TCP has a higher solubility rate. In this work, we studied the influence of magnesium and zinc in the physical-chemical properties of TCP ceramics. Magnesium increases the temperature of β-α phase transformation and zinc has been associated with bone formation. The general formula of the co-doped ceramics is (Ca{sub 1-x-y}Mg{sub x}Zn{sub y}){sub 3}(PO{sub 4}){sub 2}. The co-doped ceramics were compared with pure TCP. The powders were produced via wet synthesis from Ca(OH){sub 2}, H{sub 3}PO{sub 4}, Mg(OH) and ZnO, dried by freeze drying and calcined at 800 °C. The doping influence on the physical-chemical properties of powders were evaluated through thermal analysis, X-ray diffraction and the microstructure was analyzed by scanning electron microscopy. (author)

  6. 40 CFR 721.6000 - Tris (2,3-dibromopropyl) phosphate.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Tris (2,3-dibromopropyl) phosphate... Substances § 721.6000 Tris (2,3-dibromopropyl) phosphate. (a) Chemical substance and significant new use subject to reporting. (1) The chemical substance tris (2,3-dibromopropyl) phosphate (CAS Number...

  7. 40 CFR 721.3900 - Alkyl polyethylene glycol phosphate, potassium salt.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkyl polyethylene glycol phosphate... Specific Chemical Substances § 721.3900 Alkyl polyethylene glycol phosphate, potassium salt. (a) Chemical... as alkyl polyethylene glycol phosphate, potassium salt (P-90-481), is subject to reporting under...

  8. Chemical bond properties and charge transfer bands of O(2-)-Eu(3+), O(2-)-Mo(6+) and O(2-)-W(6+) in Eu(3+)-doped garnet hosts Ln3M5O12 and ABO4 molybdate and tungstate phosphors.

    Science.gov (United States)

    Liu, Xiaoguang; Li, Ling; Noh, Hyeon Mi; Moon, Byung Kee; Choi, Byung Chun; Jeong, Jung Hyun

    2014-06-21

    Charge transfer (CT) energy from the ligand to the central ions is an important factor in luminescence properties for rare earth doped inorganic phosphors. The dielectric theory of complex crystals was used to calculate chemical bond properties. Combining the photoluminescence and the dielectric theory of complex crystals, the CT bands of O(2-)-Eu(3+), O(2-)-Mo(6+) and O(2-)-W(6+) for Eu(3+)-doped inorganic phosphors have been investigated experimentally and theoretically. Taking Eu(3+)-doped Ln3M5O12 (Ln = Y, Lu and M = Al, Ga), Gd3Ga5O12, MMoO4 (M = Ca, Sr, Ba) and MWO4 (M = Ca, Sr, Ba) as typical phosphors, we investigated the effects of the cation size on the CT bands and chemical bond properties including the bond length (d), the covalency (fc), the bond polarizability (αb) and the environmental factor (he) of O(2-)-Eu(3+), O(2-)-Mo(6+) and O(2-)-W(6+), respectively. For systematic isostructural Ln3M5O12 (Ln = Y, Lu and M = Al, Ga) phosphors, with the increasing M ion radius, the bond length of Ln-O decreases, but fc and αb increase, which is the main reason that the environmental factor increased. For the isostructural MMoO4:Eu, with the increasing M ion radius, the Mo-O bond length increases, but fc and αb decrease, and thus he decreases. However, in the compound system MWO4:Eu (M = Ca, Ba) with the increasing M ion radius, the O-W bond length increases, but fc and αb increase, and thus he increases and the O-W CT energy decreases. Their O(2-)-Eu(3+), O(2-)-Mo(6+) and O(2-)-W(6+) CT bands as well as their full width at half maximum (FWHM) were directly influenced by he. And with the increasing he, CT bands of O-Eu or O-Mo or O-W decrease and their FWHM increases. These results indicate a promising approach for changing the material properties, searching for new Eu(3+) doped molybdate, tungstate or other oxide phosphors and analyzing the experimental result.

  9. Bond Boom

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The Ministry of Finance recently kick-started a pilot program allowing local governments of Shanghai and Shenzhen,and Zhejiang and Guangdong provinces to issue bonds for the first time.How will the new policy affect fiscal capacities of local governments and the broader economy? What else should the country do to build a healthy bond market? Economists and experts discussed these issues in an interview with the Shanghai Securities Journal.Edited excerpts follow.

  10. Bond Boom

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The Ministry of Finance recently kick-started a pilot program allowing local governments of Shanghai and Shenzhen, and Zhejiang and Guangdong provinces to issue bonds for the first time. How will the new policy affect fiscal capacities of local governments and the broader economy? What else should the country do to build a healthy bond market? Economists and experts discussed these issues in an interview with the ShanghaiSecuritiesJournal. Edited excerpts follow:

  11. The effect of Tricresyl-Phosphate (TCP) as an additive on wear of Iron (Fe)

    Science.gov (United States)

    Ghose, Hiren M.; Ferrante, John; Honecy, Frank C.

    1987-01-01

    The effect of tricresyl phosphate (TCP) as an antiwear additive in lubricant trimethyol propane triheptanoate (TMPTH) was investigated. The objective was to examine step loading wear by use of surface analysis, wetting, and chemical bonding changes in the lubricant. The investigation consisted of steploading wear studies by a pin or disk tribometer, the effects on wear related to wetting by contact angle and surface tension measurements of various liquid systems, the chemical bonding changes between lubricant and TCP chromatographic analysis, and by determining the reaction between the TCP and metal surfaces through wear scar analysis by Auger emission spectroscopy (AES). The steploading curve for the base fluid alone shows rapid increase of wear rate with load. The steploading curve for the base fluid in presence of 4.25 percent by volume TCP under dry air purge has shown a great reduction of wear rate with all loads studied. It has also been found that the addition of 4.25 percent by volume TCP plus 0.33 percent by volume water to the base lubricant under N2 purge also greatly reduces the wear rate with all loads studied. AES surface analysis reveals a phosphate type wear resistant film, which greatly increases load-bearing capacity, formed on the iron disk. Preliminary chromatographic studies suggest that this film forms either because of ester oxidation or TCP degradation. Wetting studies show direct correlation between the spreading coefficient and the wear rate.

  12. Effective removal of methyl blue by fine-structured strontium and barium phosphate nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Fan, E-mail: zhangfan0128@njau.edu.cn [College of Science, Nanjing Agricultural University, Nanjing 210095 (China); Song, Weijie [Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Lan, Jing [College of Chemistry and Pharmaceutical Sciences, Qingdao Agricultural University, Qingdao 266109 (China)

    2015-01-30

    Graphical abstract: - Highlights: • SBP nanorods have been studied for removal of methyl blue from solutions. • The high adsorption capacity was calculated to be 1691.8 mg/g. • The equilibrium reached within 10 min and obeyed the pseudo-second-order kinetics. • The mechanism was the ionic interaction, hydrogen bonds and chemical precipitation. - Abstract: In this work, the composite of strontium phosphate and barium phosphate (called SBP) nanorods have been synthesized, characterized and studied for removal of methyl blue (MB). The effects of pH, temperature, contact time, initial dye concentration on removal of MB were studied in detail. Results suggest that pH and temperature were not critical limiting factors for the removal of MB. Reaching equilibrium was very rapid (within 10 min) and the high adsorption capacity of MB by SBP nanorods was 1691.8 mg/g at initial dye concentration of 2000 mg/L. The adsorption process obeyed the pseudo-second-order kinetics model and Langmuir isotherm model. Importantly, the mechanism contributed to the MB removal was proposed to be the ionic interaction and hydrogen bonds for low dye concentration, chemical precipitation for high dye concentration. It is predicted that the SBP nanorods being an effective adsorbent for elimination of MB from colored aqueous solutions.

  13. Nature of the chemical bond in complex hydrides, NaAlH{sub 4}, LiAlH{sub 4}, LiBH{sub 4} and LiNH{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Yoshino, M. [Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya University, Chikusa-Ku, Nagoya 464-8603 (Japan)]. E-mail: yoshino@silky.numse.nagoya-u.ac.jp; Komiya, K. [Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya University, Chikusa-Ku, Nagoya 464-8603 (Japan); Takahashi, Y. [Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya University, Chikusa-Ku, Nagoya 464-8603 (Japan); Shinzato, Y. [Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya University, Chikusa-Ku, Nagoya 464-8603 (Japan); Yukawa, H. [Department of Materials Science and Engineering, Graduate School of Engineering, Nagoya University, Chikusa-Ku, Nagoya 464-8603 (Japan); Morinaga, M. [Department of Materials Science and Engineering, Graduate School of Engineering, Institute for Advanced Research, Nagoya University, Chikusa-Ku, Nagoya 464-8603 (Japan)

    2005-12-08

    The most stable crystal structures of complex hydrides, MXH{sub n} (NaAlH{sub 4}, LiAlH{sub 4}, LiBH{sub 4} and LiNH{sub 2}) were simulated by the plane-wave pseudopotential method. The local chemical bonds between constituent ions were simulated using the DV-X{alpha} molecular orbital method. As a result, it was found that the covalent interaction is operating between X and H ions to form a XH{sub n} ion in MXH{sub n}. In addition, the ionic interaction is operating between M and XH{sub n} ions through the charge transfer from M to XH{sub n} ions. On the basis of this understanding of the nature of the chemical bond between ions, a phase stability diagram of complex hydrides was proposed using two parameters. One is the bond energy of XH diatomic molecules and the other is electronegativity difference, {delta}{phi}{sub X-M}, between M and X ions. The calculated stability change by doping into NaAlH{sub 4} could by explained qualitatively following this diagram. This diagram will provide us a clue to the modification of hydrides to lower the hydrogen decomposition temperature.

  14. Bond strength of direct and indirect bonded brackets after thermocycling.

    Science.gov (United States)

    Daub, Jacob; Berzins, David W; Linn, Brandon James; Bradley, Thomas Gerard

    2006-03-01

    Thermocycling simulates the temperature dynamics in the oral environment. With direct bonding, thermocycling reduces the bond strength of orthodontic adhesives to tooth structure. The purpose of this study was to evaluate the shear bond strengths (SBS) of one direct and two indirect bonding methods/adhesives after thermocycling. Sixty human premolars were divided into three groups. Teeth in group 1 were bonded directly with Transbond XT. Teeth in group 2 were indirect bonded with Transbond XT/Sondhi Rapid Set, which is chemically cured. Teeth in group 3 were indirect bonded with Enlight LV/Orthosolo and light cured. Each sample was thermocycled between 5 degrees C and 55 degrees C for 500 cycles. Mean SBS in groups 1, 2, and 3 were not statistically significantly different (13.6 +/- 2.9, 12.3 +/- 3.0, and 11.6 +/- 3.2 MPa, respectively; P > .05). However, when these values were compared with the results of a previous study using the same protocol, but without thermocycling, the SBS was reduced significantly (P = .001). Weibull analysis further showed that group 3 had the lowest bonding survival rate at the minimum clinically acceptable bond-strength range. The Adhesive Remnant Index was also determined, and group 2 had a significantly (P bond failures at the resin/enamel interface.

  15. Why nature chose phosphates.

    Science.gov (United States)

    Westheimer, F H

    1987-03-06

    Phosphate esters and anhydrides dominate the living world but are seldom used as intermediates by organic chemists. Phosphoric acid is specially adapted for its role in nucleic acids because it can link two nucleotides and still ionize; the resulting negative charge serves both to stabilize the diesters against hydrolysis and to retain the molecules within a lipid membrane. A similar explanation for stability and retention also holds for phosphates that are intermediary metabolites and for phosphates that serve as energy sources. Phosphates with multiple negative charges can react by way of the monomeric metaphosphate ion PO3- as an intermediate. No other residue appears to fulfill the multiple roles of phosphate in biochemistry. Stable, negatively charged phosphates react under catalysis by enzymes; organic chemists, who can only rarely use enzymatic catalysis for their reactions, need more highly reactive intermediates than phosphates.

  16. Genetic analysis of the Fourier-transform infrared spectra of bovine milk with emphasis on individual wavelengths related to specific chemical bonds.

    Science.gov (United States)

    Bittante, G; Cecchinato, A

    2013-09-01

    transmittance, and the heritability estimates of individual waves were generally very low (with some exceptions). The 3 other identified regions contained many transmittance peaks that represented important chemical bonds; these showed much lower phenotypic and genetic variability in terms of individual waves, but relatively higher and less variable heritability estimates. Among them, the SWIR region (near-infrared) showed a peculiar cyclic pattern of the heritability coefficients of transmittance, the MWIR-1 region was particularly important for the estimation of fat, and the MWIR-LWIR region (also known also as the "fingerprint region") had 3 areas of relatively high heritability. In summary, we found that the transmittance data from the FTIR spectra of milk have genetic variability that may prove useful for the direct genetic improvement of dairy species, rather than only through indirect phenotypic predictions of individual milk quality and technological traits.

  17. Core level photoemission spectroscopy and chemical bonding in Sr2Ta2O7

    DEFF Research Database (Denmark)

    Atuchin, V. V.; Grivel, Jean-Claude; Zhang, Z. M.

    2009-01-01

    structural and XPS data for other Sr- and Ta-containing oxide compounds. The new data point for Sr2Ta2O7 is consistent with the previously derived relationship for a set of Sr-bearing oxides. The binding energy difference Delta(O-Sr) was found to decrease with increasing bond distance L(Sr-O)....

  18. Sintering of calcium phosphate bioceramics.

    Science.gov (United States)

    Champion, E

    2013-04-01

    Calcium phosphate ceramics have become of prime importance for biological applications in the field of bone tissue engineering. This paper reviews the sintering behaviour of these bioceramics. Conventional pressureless sintering of hydroxyapatite, Ca10(PO4)6(OH)2, a reference compound, has been extensively studied. Its physico-chemistry is detailed. It can be seen as a competition between two thermally activated phenomena that proceed by solid-state diffusion of matter: densification and grain growth. Usually, the objective is to promote the first and prevent the second. Literature data are analysed from sintering maps (i.e. grain growth vs. densification). Sintering trajectories of hydroxyapatite produced by conventional pressureless sintering and non-conventional techniques, including two-step sintering, liquid phase sintering, hot pressing, hot isostatic pressing, ultrahigh pressure, microwave and spark plasma sintering, are presented. Whatever the sintering technique may be, grain growth occurs mainly during the last step of sintering, when the relative bulk density reaches 95% of the maximum value. Though often considered very advantageous, most assisted sintering techniques do not appear very superior to conventional pressureless sintering. Sintering of tricalcium phosphate or biphasic calcium phosphates is also discussed. The chemical composition of calcium phosphate influences the behaviour. Similarly, ionic substitutions in hydroxyapatite or in tricalcium phosphate create lattice defects that modify the sintering rate. Depending on their nature, they can either accelerate or slow down the sintering rate. The thermal stability of compounds at the sintering temperature must also be taken into account. Controlled atmospheres may be required to prevent thermal decomposition, and flash sintering techniques, which allow consolidation at low temperature, can be helpful.

  19. Physicochemical characterization of zinc-substituted calcium phosphates

    Indian Academy of Sciences (India)

    DOROTA WALCZYK; DAGMARA MALINA; MILENA KRÓL; KLAUDIA PLUTA; AGNIESZKA SOBCZAK-KUPIEC

    2016-04-01

    Biocompatible and bioactive calcium phosphates can make chemical bonds with living bones. Improvement of their biological and physicochemical properties can be achieved by doping with various ions that are presented in natural apatites of bones. These substitutions influence lattice parameters, structure and morphology of apatites. In recent times great attention has been devoted to zinc ions that are the second most abundant trace element present in bones. Zinc embedded into calcium phosphate may enhance the bone formation and in addition exhibits antifungal and antibacterial properties. Therefore, it is rational to form structures incorporated with this ion. In this paper the incorporation of the Zn ions into natural and synthetic calcium phosphates has been reported.Natural hydroxyapatites (HAs) applied in this study were derived mainly from pork bones whereas both brushite and synthetic were formed using wet chemical methods. Ambient temperature synthesis leads to the formation ofbrushite, whereas the process performed at elevated temperature gives HA. Subsequently, attained structures were modified with Zn ions by using in situ or sorption procedures. Phase composition and morphology of obtained materials were determined by means of X-ray diffractometry, Fourier transform infrared spectroscopy and scanning electron microscopy equipped with energy-dispersive spectroscopy. Introduced XRD patterns depict changes of the crystallinity of HA with the increase in the amount of embedded zinc ions. On the contrary, no changes of the crystallinity were observed for the brushite doped with Zn ions. Morphology of attained powders, visualized using scanningelectron microscopy exemplified structural changes between calcium phosphates conjugated with zinc ions. Many authors report that the addition of small amounts of Zn ions leads to loss of crystallinity and decrease of lattice parameters. Interestingly, upon addition of Zn ions to the natural and synthetic HAp by sorption

  20. Optimising hydrogen bonding in solid wood

    DEFF Research Database (Denmark)

    Engelund, Emil Tang

    2009-01-01

    The chemical bonds of wood are both covalent bonds within the wood polymers and hydrogen bonds within and between the polymers. Both types of bonds are responsible for the coherence, strength and stiffness of the material. The hydrogen bonds are more easily modified by changes in load, moisture...... and temperature. The distribution of bond lengths was examined using infrared spectroscopy (ATR-FTIR) both prior to treatments and after. The results show that the absorbance bands of the spectra related to the hydroxyl and carboxyl stretching vibrations were changed by the treatments. Apparently, the first...

  1. Nanoscale Bonding between Human Bone and Titanium Surfaces: Osseohybridization

    Directory of Open Access Journals (Sweden)

    Jun-Sik Kim

    2015-01-01

    Full Text Available Until now, the chemical bonding between titanium and bone has been examined only through a few mechanical detachment tests. Therefore, in this study, a sandblasted and acid-etched titanium mini-implant was removed from a human patient after 2 months of placement in order to identify the chemical integration mechanism for nanoscale osseointegration of titanium implants. To prepare a transmission electron microscopy (TEM specimen, the natural state was preserved as much as possible by cryofixation and scanning electron microscope/focused ion beam (SEM-FIB milling without any chemical treatment. High-resolution TEM (HRTEM, energy dispersive X-ray spectroscopy (EDS, and scanning TEM (STEM/electron energy loss spectroscopic analysis (EELS were used to investigate the chemical composition and structure at the interface between the titanium and bone tissue. HRTEM and EDS data showed evidence of crystalline hydroxyapatite and intermixing of bone with the oxide layer of the implant. The STEM/EELS experiment provided particularly interesting results: carbon existed in polysaccharides, calcium and phosphorus existed as tricalcium phosphate (TCP, and titanium existed as oxidized titanium. In addition, the oxygen energy loss near edge structures (ELNESs showed a possibility of the presence of CaTiO3. These STEM/EELS results can be explained by structures either with or without a chemical reaction layer. The possible existence of the osseohybridization area and the form of the carbon suggest that reconsideration of the standard definition of osseointegration is necessary.

  2. Tensile bond strength of resin luting cement to glass infiltrated porous aluminium oxide cores (In-Ceram).

    Science.gov (United States)

    Isidor, F; Stokholm, R; Ravnholt, G

    1995-09-01

    The effect of various methods of surface treatment of glass infiltrated aluminium oxide (In-Ceram) on tensile bond strength was evaluated. Test specimens were formed as bars. After surface treatment of the flat ends, two bars were bonded together with either a dual curing resin (Twinlook) or a chemical curing resin with a phosphate monomer (Panavia Ex). After cementation the specimens were stored in humid conditions for 1 week and then thermocycled 1,000 times between 15 degrees C and 60 degrees C. The highest median tensile bond strengths were obtained with the Silicoater MD-method without the Opaquer and Twinlook as luting agent (23.9 MPa) or with sandblasting with 250 micrometers Al2O3 particles and Panavia Ex as luting agent (22.0 MPa).

  3. Phosphorus-31, sup 15 N, and sup 13 C NMR of glyphosate: Comparison of pH titrations to the herbicidal dead-end complex with 5-enolpyruvoylshikimate-3-phosphate synthase

    Energy Technology Data Exchange (ETDEWEB)

    Castellino, S.; Leo, G.C.; Sammons, R.D.; Sikorski, J.A. (Monsanto Agricultural Company, St. Louis, MO (USA))

    1989-05-02

    The herbicidal dead-end ternary complex (E{sup S3P}{sub Glyph}) of glyphosate (N-(phosphonomethyl)glycine) with 5-enolpyruvoylshikimate-3-phosphate synthase (EPSPS) and the substrate shikimate 3-phosphate (S3P) has been characterized by {sup 31}P, {sup 15}N, and {sup 13}C NMR. The NMR spectra of EPSPS-bound glyphosate show unique chemical shifts ({delta}) for each of the three nuclei. By {sup 31}P NMR, glyphosate in the dead-end complex is a distinct species 3.5 ppm downfield from free glyphosate. The {sup 13}C signal of glyphosate in the dead-end complex is shifted 4 ppm downfield from that of free glyphosate. The {sup 15}N signal for glyphosate (99%) in the dead-end complex is 5 ppm further downfield than that of any free zwitterionic species and 10 ppm downfield from that of the average free species at pH 10.1. The structures of each ionic state of glyphosate are modeled with force field calculations by using MacroModel. A correlation is made for the {sup 31}P {delta} and the C-P-O bond angle, and the {sup 13}C and {sup 15}N {delta} values are postulated to be related to C-C-O and C-N-C bond angles, respectively. The downfield {sup 31}P chemical shift perturbation for S3P in the EPSPS binary complex is consistent with ionization of the 3-phosphate of S3P upon binding. Comparison with the S3P {sup 31}P {delta} vs pH titration curve specifies predominantly the dianion of the 3-phosphate in the E{sup S3P} binary complex, while the E{sup S3P}{sub Glyph} complex indicates net protonation at the 3-phosphate. Chemical shift perturbations of this latter type may be explained by changes in the O-P-O bond angle.

  4. IR Vibrational spectra of H-bonded complexes of adenine, 2-aminopurine and 2-aminopurine+ with cytosine and thymine: Quantum-chemical study

    Science.gov (United States)

    Brovarets', O. O.; Hovorun, D. M.

    2011-11-01

    Using theoretical study on the B3LYP/6-311++G(d,p) level of theory, we have compared vibrational spectra of 2-aminopurine (as neutral or protonated at N1 atom species) with adenine and H-bonded complexes of 2-aminopurine (as neutral or protoned at N1 atom species) · cytosine or 2-aminopurine · thymine with adenine · cytosine and adenine · thymine base pairs. The nature of the base pairing between adenine, 2-aminopurine, 2-aminopurine+ and cytosine or thymine have been investigated by means of quantum-mechanical calculations. We have investigated the effect of the hydrogen bond formation on the vibrational spectra of the investigated base pairs. The main differences in the vibrational spectra as for bases so for base pairs have been observed in the high-frequency region.

  5. Discussion about magnesium phosphating

    Directory of Open Access Journals (Sweden)

    P. Pokorny

    2016-07-01

    Full Text Available The paper describes results from recently published research focused on production of non-conventional magnesium phosphate Mg3(PO42・4H2O – bobierrite, or MgHPO4・3H2O – newberyite coating for both magnesium alloys and/or mild steel. This new kind of coating is categorized in the context of current state of phosphating technology and its potential advantages and crystal structure is discussed. At the same time, the suitable comparison techniques for magnesium phosphate coating and conventional zinc phosphate coating are discussed.

  6. Ligand size dependence of U-N and U-O bond character in a series of uranyl hexaphyrin complexes: quantum chemical simulation and density based analysis.

    Science.gov (United States)

    Di Pietro, Poppy; Kerridge, Andrew

    2017-03-02

    A series of uranyl complexes with hexaphyrin ligands are investigated at the density functional level of theory and analysed using a variety of density-based techniques. A relationship is identified between the size of the ligand and the stability of the complex, controlled by the presence of meso-carbon centres in the porphyrin ring. The complex with the smallest ligand, cyclo[6]pyrrole, is found to have enhanced covalent character in equatorial U-N bonds as defined by the quantum theory of atoms in molecules (QTAIM), as well as enhanced stability, compared to the larger complexes. QTAIM data are supported by electron density difference distributions, integrated electronic properties and analysis of the reduced density gradient (RDG), which all show unambiguous evidence of electron sharing in all U-N bonds. In all complexes, a weakening of the covalent axial U-Oyl interaction in comparison to free uranyl is found, with evidence for a separation of electronic charge resulting in a more ionic interaction. A relationship between covalent character in the U-N bonds and the magnitude of uranyl charge redistribution is identified, where the greater the covalent character of the U-N interaction, the more ionic the U-Oyl interaction appears. The complex with the largest ligand, hexaphyrin(1.1.1.1.1.1), is found to have additional interactions with the uranyl oxygen centres, perturbing the U-Oyl interaction.

  7. Ab initio investigations of the electronic structures and chemical bonding in LiCo{sub 6}P{sub 4} and Li{sub 2}Co{sub 12}P{sub 7}

    Energy Technology Data Exchange (ETDEWEB)

    Matar, Samir F. [CNRS, ICMCB, UPR 9048, F‐33600 Pessac (France); Université de Bordeaux, ICMCB, UPR 9048, F‐33600 Pessac (France); Al-Alam, Adel; Ouaini, Naïm [Université Saint-Esprit de Kaslik (USEK), Groupe OCM (Optimization et Caractérisation des Matériaux), CSR-USEK, CNRS-L, Jounieh (Lebanon); Pöttgen, Rainer, E-mail: pottgen@uni-muenster.de [Institut für Anorganische und Analytische Chemie, Universität Münster, Corrensstraße 30, D-48149 Münster (Germany)

    2013-06-15

    The electronic structures of the metal-rich phosphides LiCo{sub 6}P{sub 4} and Li{sub 2}Co{sub 12}P{sub 7} were studied by DFT calculations. Both phosphides consist of three-dimensional [Co{sub 6}P{sub 4}] and [Co{sub 12}P{sub 7}] polyanionic networks which leave hexagonal channels for the lithium atoms. COOP data show strong Co–P and Co–Co bonding within the polyanions. The lithium atoms have trigonal prismatic phosphorus coordination. Total energy calculations indicate stability upon de-lithiation towards the Co{sub 6}P{sub 4} and Co{sub 12}P{sub 7} substructures - Graphical abstract: The cobalt–phosphorus networks in LiCo{sub 6}P{sub 4} and Li{sub 2}Co{sub 12}P{sub 7}. - Highlights: • Chemical bonding resolved in the metal-rich phosphides LiCo{sub 6}P{sub 4} and Li{sub 2}Co{sub 12}P{sub 7}. • Strong covalent Co–P bonding character in the [Co{sub 6}P{sub 4}] and [Co{sub 12}P{sub 7}] substructures. • Total energy calculations indicate stability of the de-lithiated substructures.

  8. 水对液相氧化处理聚乙烯木塑复合材胶接性能的影响%Effect of water on bonding properties for liquidoid chemical oxidation treated wood/PE composites

    Institute of Scientific and Technical Information of China (English)

    滕晓磊; 邸明伟

    2011-01-01

    The surface of wood/polyethylene (PE) composites was treated by liquidoid chemical oxidation to improve its adhesion properties.The water-resistance of treated wood/PE composites bonding joint was studied and the failure mechanism at soaking in water for the bonding joint was investigated by using analysis of contact angle,scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) through effect of water on the surface properties of treated wood/PE composites in soaking experiments.The results showed that the untreated wood/PE composites were hard to be adhered due to the polyethylene component gathered on the surface of composites, and the bonding strength and water-resistance for wood/PE composites bonding joint were improved after liquidoid chemical oxidation treatment.Water showed a remarkable effect on the surface properties for oxidation treated wood/PE composites,the surface structure changed and the crack appeared on the surface due to the moisture absorption and expansion of the wood fiber within composites under soaking in water,which resulted in the failure of bonding joint for wood/PE composites.%采用液相氧化方法对木粉/聚乙烯木塑复合材料进行表面处理以改善其胶接性能研究了氧化处理后木塑复合材料胶接接头的耐水性,并利用接触角测试、SEM、FT-IR等分析手段,探讨了木塑复合材料胶接接头在水环境下的老化失效原因 结果表明,未处理的聚乙烯木塑复合材料难以胶接,经过液相氧化处理后,不但可以提高聚乙烯木塑复合材料的胶接强度,还可改善木塑复合材料胶接接头的耐水性 在水的作用下,液相氧化处理聚乙烯木塑复合材的表面结构会发生改变,复合材料中木质纤维的吸水膨胀也会导致材料表面出现裂纹,致使胶接接头失效.

  9. Electronic, optical properties and chemical bonding in six novel 1111-like chalcogenide fluorides AMChF (A=Sr, Ba; M=Cu, Ag; and Ch=S, Se, Te) from first principles calculations

    Energy Technology Data Exchange (ETDEWEB)

    Bannikov, V.V.; Shein, I.R. [Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, 620990 Ekaterinburg (Russian Federation); Ivanovskii, A.L., E-mail: ivanovskii@ihim.uran.ru [Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, 620990 Ekaterinburg (Russian Federation)

    2012-12-15

    Employing first-principles band structure calculations, we have examined the electronic, optical properties and the peculiarities of the chemical bonding for six newly synthesized layered quaternary 1111-like chalcogenide fluorides SrAgSF, SrAgSeF, SrAgTeF, BaAgSF, BaAgSeF, and SrCuTeF, which are discussed in comparison with some isostructural 1111-like chalcogenide oxides. We found that all of the studied phases AMChF (A=Sr, Ba; M=Cu, Ag; and Ch=S, Se, Te) are semiconductors for which the fitted 'experimental' gaps lie in the interval from 2.23 eV (for SrAgSeF) to 3.07 eV (for SrCuTeF). The near-Fermi states of AMChF are formed exclusively by the valence orbitals of the atoms from the blocks (MCh); thus, these phases belong to the layered materials with 'natural multiple quantum wells'. The bonding in these new AMChF phases is described as a high-anisotropic mixture of ionic and covalent contributions, where ionic M-Ch bonds together with covalent M-Ch and Ch-Ch bonds take place inside blocks (MCh), while inside blocks (AF) and between the adjacent blocks (MCh)/(AF) mainly ionic bonds emerge. - Graphical Abstract: Isoelectronic surface for SrAgSeF and atomic-resolved densities of states for SrAgTeF, and SrCuTeF. Highlights: Black-Right-Pointing-Pointer Very recently six new layered 1111-like chalcogenide fluorides AMChF were synthesized. Black-Right-Pointing-Pointer Electronic, optical properties for AMChF phases were examined from first principles. Black-Right-Pointing-Pointer All these materials are characterized as non-magnetic semiconductors. Black-Right-Pointing-Pointer Bonding is highly anisotropic and includes ionic and covalent contributions. Black-Right-Pointing-Pointer Introduction of magnetic ions in AMChF is proposed for search of novel magnetic materials.

  10. Mechanisms of phosphate removal from aqueous solution by blast furnace slag and steel furnace slag

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    We report the adsorption of phosphate and discuss the mechanisms of phosphate removal from aqueous solution by burst furnace slag (BFS) and steel furnace slag (SFS). The results show that the adsorption of phosphate on the slag was rapid and the majority of adsorption was completed in 5~10 min. The adsorption capacity of phosphate by the slag was reduced dramatically by acid treatment. The relative contribution of adsorption to the total removal of phosphate was 26%~28%. Phosphate adsorption on BFS and SFS follows the Freundlich isotherm, with the related constants ofk 6.372 and 1/n 1.739 for BFS, and ofk 1.705 and 1/n 1.718 for SFS. The pH and Ca2+ concentration were decreased with the addition of phosphate, suggesting the formation of calcium phosphate precipitation. At pH 2.93 and 6.93, phosphate was desorbed by about 36%~43% and 9%~11%, respectively.These results indicate that the P adsorption on the slag is not completely reversible and that the bond between the slag particles and adsorbed phosphate is strong. The X-ray diffraction (XRD) patterns of BFS and SFS before and after phosphate adsorption verify SFS is related to the formation of phosphate calcium precipitation and the adsorption on hydroxylated oxides. The results show that BFS and SFS removed phosphate nearly 100%, indicating they are promising adsorbents for the phosphate removal in wastewater treatment and pollution control.

  11. The chemisorptive bond basic concepts

    CERN Document Server

    Clark, Alfred

    1974-01-01

    The Chemisorptive Bond: Basic Concepts describes the basic concepts of the chemisorptive bond on solid surfaces from the simple analogies with ordinary chemical bonds to the quantum-mechanical approaches.This book is composed of 10 chapters and begins with discussions of simple formulas for correlating measurable quantities in chemisorptions and catalysis. The succeeding chapters deal with theories based on quantum-mechanical principles that describe the mutual interactions of atoms of the solid and foreign atoms on the surface. The remaining chapters consider the possible arrangements

  12. Relation between bond-length alternation and two-photon absorption of a push pull conjugated molecules: a quantum-chemical study

    Science.gov (United States)

    Bartkowiak, W.; Zaleśny, R.; Leszczynski, J.

    2003-02-01

    The results of the semiempirical study of the structure/property relationships for the two-photon absorption cross-section ( δ) of a series of prototypical π-conjugated push-pull molecules are presented. The calculations of δ for the first charge-transfer (CT) excited state were performed as a function of the bond length alternation (BLA). The molecular hyperpolarizabilities ( β and γ) were calculated using the finite-field (FF) method. The obtained data were analyzed based on the simple two-state models. A strong dependence of δ on the BLA parameter was noticed.

  13. Relation between bond-length alternation and two-photon absorption of a push-pull conjugated molecules: a quantum-chemical study

    Energy Technology Data Exchange (ETDEWEB)

    Bartkowiak, W.; Zalesny, R.; Leszczynski, J

    2003-02-01

    The results of the semiempirical study of the structure/property relationships for the two-photon absorption cross-section ({delta}) of a series of prototypical {pi}-conjugated push-pull molecules are presented. The calculations of {delta} for the first charge-transfer (CT) excited state were performed as a function of the bond length alternation (BLA). The molecular hyperpolarizabilities ({beta} and {gamma}) were calculated using the finite-field (FF) method. The obtained data were analyzed based on the simple two-state models. A strong dependence of {delta} on the BLA parameter was noticed.

  14. In Situ Laser Coating of Calcium Phosphate on TC4 Surface for Enhancing Bioactivity

    Institute of Scientific and Technical Information of China (English)

    DENG Chi; WANG Yong; ZHANG Ya-ping; GAO Jia-cheng

    2007-01-01

    Titanium alloy has been a successful implant material owing to its excellent ratio of strength to weight,toughness, and bio-inert oxide surface. Significant progress has been made in improving the bioactivity of titanium alloy by coating its oxide surface with calcium phosphates. In the present study, in situ coating was reported on Ti6Al4V(TC4) surface with calcium phosphate (Ca-P) bioceramics synthesized and synchronously cladded by laser beam. This coating was grown by first preplacing directly the raw powders, which contain 80% of CaHPO4 ·2H2O, 20% of CaCO3, and dram of rare earth (RE), on the TC4 surfaces, and then exposing the surfaces to the laser beam with a power density of 12. 73-15.27 MW · m-2 and a scanning velocity of 10. 5 m/s. The resultant coating was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis and Different-thermal Scanning (TG-DSC), and Energy Dispersive X-ray Detection (EDX). The results show that these laser ceramics include hydroxyapatite (HA), tricalcium phosphate (TCP), Ca2P2O7, and other Ca-P phases, and the interface between the coating and the TC4 substrate has tighter fixation, in which the chemical bonding is approved. These laser hybrid coatings are useful in enhancing the bioactivity of titanium alloy surfaces.

  15. Potentiometric and ³¹P NMR studies on inositol phosphates and their interaction with iron(III) ions.

    Science.gov (United States)

    Sala, Martin; Makuc, Damjan; Kolar, Jana; Plavec, Janez; Pihlar, Boris

    2011-03-01

    Potentiometric, conductometric and ³¹P NMR titrations have been applied to study interactions between myo-inositol hexakisphosphate (phytic acid), (±)-myo-inositol 1,2,3,5-tetrakisphosphate and (±)-myo-inositol 1,2,3-trisphosphate with iron(III) ions. Potentiometric and conductometric titrations of myo-inositol phosphates show that addition of iron increases acidity and consumption of hydroxide titrant. By increasing the Fe(III)/InsP(6) ratio (from 0.5 to 4) 3 mol of protons are released per 2 mol of iron(III). At first, phytates coordinate iron octahedrally between P2 and P1,3. The second coordination site represents P5 and neighbouring P4,6 phosphate groups. Complexation is accompanied with the deprotonation of P1,3 and P4,6 phosphate oxygens. At higher concentration of iron(III) intermolecular P-O-Fe-O-P bonds trigger formation of a polymeric network and precipitation of the amorphous Fe(III)-InsP(6) aggregates. (31)P NMR titration data complement the above results and display the largest chemical shift changes at pD values between 5 and 10 in agreement with strong interactions between iron and myo-inositol phosphates. The differences in T(1) relaxation times of phosphorous atoms have shown that phosphate groups at positions 1, 2 and 3 are complexated with iron(III). The interactions between iron(III) ions and inositol phosphates depend significantly on the metal to ligand ratio and an attempt to coordinate more than two irons per InsP(6) molecule results in an unstable heterogeneous system.

  16. Binary and Ternary Heterometallic (La3+, Gd3+, Y3+–Eu3+ Functionalized SBA-15 Mesoporous Hybrids: Chemically Bonded Assembly and Photoluminescence

    Directory of Open Access Journals (Sweden)

    Yan Bing

    2010-01-01

    Full Text Available Abstract A novel kind of organic–inorganic monomer SUASi has been achieved by modifying 5-sulfosalicylic acid (SUA with 3-aminopropyltrimethoxysilane (APS, subsequently binary and ternary Eu3+ mesoporous hybrid materials with 5-sulfosalicylic acid (SUA-functionalized SBA-15 and 1,10-phenanthroline (phen are synthesized by co-condensation of SUASi and TEOS in the presence of Eu3+ complex and Pluronic P123 as a template. Finally, luminescent hybrid mesoporous materials consisting of active rare earth ions (Eu3+—inert rare earth ions (Y3+, La3+, Gd3+ complex covalently bonded to the mesoporous materials network have been obtained via this sol–gel approach. The physical characterization and photoluminescence of all these resulting materials are studied in detail. Especially the luminescent behavior has been studied with the different ratios of Eu3+–(Y3+, La3+, Gd3+, which suggests that the existence of inert rare earth ions can enhance the luminescence intensity of Eu3+. This may be due to the intramolecular energy transfer between Y3+, La3+, Gd3+, and Eu3+ through the covalently bonded mesoporous framework.

  17. Direct, simple derivatization of disulfide bonds in proteins with organic mercury in alkaline medium without any chemical pre-reducing agents

    Energy Technology Data Exchange (ETDEWEB)

    Campanella, Beatrice; Onor, Massimo [National Research Council of Italy, C.N.R., Istituto di Chimica dei Composti Organo Metallici-ICCOM- UOS Pisa, Area di Ricerca, Via G. Moruzzi 1, 56124 Pisa (Italy); Ferrari, Carlo [National Research Council of Italy, C.N.R., Istituto Nazionale di Ottica, INO-UOS Pisa, Area di Ricerca, Via G. Moruzzi 1, 56124 Pisa (Italy); D’Ulivo, Alessandro [National Research Council of Italy, C.N.R., Istituto di Chimica dei Composti Organo Metallici-ICCOM- UOS Pisa, Area di Ricerca, Via G. Moruzzi 1, 56124 Pisa (Italy); Bramanti, Emilia, E-mail: bramanti@pi.iccom.cnr.it [National Research Council of Italy, C.N.R., Istituto di Chimica dei Composti Organo Metallici-ICCOM- UOS Pisa, Area di Ricerca, Via G. Moruzzi 1, 56124 Pisa (Italy)

    2014-09-16

    Highlights: • A simple procedure for the derivatization of proteins disulfide bonds. • Cysteine groups in several proteins derivatised with pHMB in alkaline media. • 75–100% labelling of cysteines in proteins with pHMB. - Abstract: In this work we have studied the derivatization of protein disulfide bonds with p-Hydroxymercurybenzoate (pHMB) in strong alkaline medium without any preliminary reduction. The reaction has been followed by the determination of the protein–pHMB complex using size exclusion chromatography coupled to a microwave/UV mercury oxidation system for the on-line oxidation of free and protein-complexed pHMB and atomic fluorescence spectrometry (SEC–CVG–AFS) detection. The reaction has been optimized by an experimental design using lysozyme as a model protein and applied to several thiolic proteins. The proposed method reports, for the first time, that it is possible to label 75–100% cysteines of proteins and, thus, to determine thiolic proteins without the need of any reducing step to obtain reduced -SH groups before mercury labelling. We obtained a detection limit of 100 nmol L{sup −1} based on a signal-to-noise ratio of 3 for unbound and complexed pHMB, corresponding to a detection limit of proteins ranged between 3 and 360 nmol L{sup −1}, depending on the number of cysteines in the protein sequence.

  18. Radioactivity of phosphate mineral products

    OpenAIRE

    Mitrović Branislava; Vitorović Gordana; Stojanović Mirjana; Vitorović Duško

    2011-01-01

    The phosphate industry is one of the biggest polluters of the environment with uranium. Different products are derived after processing phosphoric ore, such as mineral and phosphate fertilizers and phosphate mineral supplements (dicalcium-and monocalcium phosphate) for animal feeding. Phosphate mineral additives used in animal food may contain a high activity of uranium. Research in this study should provide an answer to the extent in which phosphate minera...

  19. The structure, energetics, and nature of the chemical bonding of phenylthiol adsorbed on the Au(111) surface: implications for density-functional calculations of molecular-electronic conduction.

    Science.gov (United States)

    Bilić, Ante; Reimers, Jeffrey R; Hush, Noel S

    2005-03-01

    The adsorption of phenylthiol on the Au(111) surface is modeled using Perdew and Wang density-functional calculations. Both direct molecular physisorption and dissociative chemisorption via S-H bond cleavage are considered as well as dimerization to form disulfides. For the major observed product, the chemisorbed thiol, an extensive potential-energy surface is produced as a function of both the azimuthal orientation of the adsorbate and the linear translation of the adsorbate through the key fcc, hcp, bridge, and top binding sites. Key structures are characterized, the lowest-energy one being a broad minimum of tilted orientation ranging from the bridge structure halfway towards the fcc one. The vertically oriented threefold binding sites, often assumed to dominate molecular electronics measurements, are identified as transition states at low coverage but become favored in dense monolayers. A similar surface is also produced for chemisorption of phenylthiol on Ag(111); this displays significant qualitative differences, consistent with the qualitatively different observed structures for thiol chemisorption on Ag and Au. Full contours of the minimum potential energy as a function of sulfur translation over the crystal face are described, from which the barrier to diffusion is deduced to be 5.8 kcal mol(-1), indicating that the potential-energy surface has low corrugation. The calculated bond lengths, adsorbate charge and spin density, and the density of electronic states all indicate that, at all sulfur locations, the adsorbate can be regarded as a thiyl species that forms a net single covalent bond to the surface of strength 31 kcal mol(-1). No detectable thiolate character is predicted, however, contrary to experimental results for alkyl thiols that indicate up to 20%-30% thiolate involvement. This effect is attributed to the asymptotic-potential error of all modern density functionals that becomes manifest through a 3-4 eV error in the lineup of the adsorbate and

  20. Definition and Application of Topological Index Based on Bond Connectivity

    Institute of Scientific and Technical Information of China (English)

    WANG Zhen-dong; YANG Feng; YANG Hai-lang; LUO Ming-dao; QU Song-sheng

    2003-01-01

    Bond connectivity topological index Si based on chemical bonds was defined by using a matrix method.And Si is formed by atomic parameters such as the number of valence electrons,the number of the highest main quantum of atoms and the bonding electrons and bond parameters such as the length of bonds,the electronegativity difference of bonding atoms.The molecular bond connectivity topological index S is composed of Si.The thermodynamic properties of saturated hydrocarbons,unsaturated hydrocarbons,oxygen organic,methane halide and transitional element compounds and the molecular bond connectivity topological index S have an optimal correlative relationship.

  1. Research and engineering assessment of biological solubilization of phosphate

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, R.D.; McIlwain, M.E.; Losinski, S.J.; Taylor, D.D.

    1993-03-01

    This research and engineering assessment examined a microbial phosphate solubilization process as a method of recovering phosphate from phosphorus containing ore compared to the existing wet acid and electric arc methods. A total of 860 microbial isolates, collected from a range of natural environments were tested for their ability to solubilize phosphate from rock phosphate. A bacterium (Pseudomonas cepacia) was selected for extensive characterization and evaluation of the mechanism of phosphate solubilization and of process engineering parameters necessary to recover phosphate from rock phosphate. These studies found that concentration of hydrogen ion and production of organic acids arising from oxidation of the carbon source facilitated microbial solubilization of both pure chemical insoluble phosphate compounds and phosphate rock. Genetic studies found that phosphate solubilization was linked to an enzyme system (glucose dehydrogenase). Process-related studies found that a critical solids density of 1% by weight (ore to liquid) was necessary for optimal solubilization. An engineering analysis evaluated the cost and energy requirements for a 2 million ton per year sized plant, whose size was selected to be comparable to existing wet acid plants.

  2. Tetramethylammonium dihydrogen phosphate hemihydrate

    Directory of Open Access Journals (Sweden)

    Kyoko Fujita

    2009-04-01

    Full Text Available In the crystal structure of the title compound, C4H12N+·H2PO4−·0.5H2O, the anions form an infinite hydrogen-bonded chain along the [1overline{1}0] direction. The anion chains are connected by water molecules, which lie on crystallographic twofold rotation axes, through O—H...O hydrogen bonds. These hydrogen bonds are almost perpendicular to the other hydrogen bonds which create an assembled structure of anions. In addition, C—H...O hydrogen bonds between anions and cations are observed.

  3. Effect of chromatographic conditions on retention behavior and system efficiency for HPTLC of selected psychotropic drugs on chemically bonded stationary phases.

    Science.gov (United States)

    Petruczynik, Anna; Wróblewski, Karol; Waksmundzka-Hajnos, Monika

    2015-01-01

    Selected psychotropic drug standards have been chromatographed on RP18, CN and diol layers with a variety of aqueous and nonaqueous mobile phases. The effect of buffers at acidic or basic pH, acetic acid, ammonia and diethylamine (DEA) in aqueous mobile phases on retention, efficiency and peak symmetry was examined. Improved peak symmetry and separation selectivity for investigated compounds were observed when ammonia or DEA were used as mobile phase additives. The effect of diethylamine concentration in aqueous eluents on retention, peak symmetry and theoretical plate number obtained on CN plates was also investigated. Because of the strong retention of these basic drugs on stationary phases bonded on silica matrix, nonaqueous eluents containing medium polar diluents, strongly polar modifiers and silanol blockers (ammonia or diethylamine) were applied. Aqueous and nonaqueous eluent systems with the best selectivity and efficiency were used for separate psychotropic drug standards' mixture on CN layer by 2D TLC.

  4. Predicted Chemical Activation Rate Constants for HO2 + CH2NH: The Dominant Role of a Hydrogen-Bonded Pre-reactive Complex.

    Science.gov (United States)

    Ali, Mohamad Akbar; Sonk, Jason A; Barker, John R

    2016-09-15

    The reaction of methanimine (CH2NH) with the hydroperoxy (HO2) radical has been investigated by using a combination of ab initio and density functional theory (CCSD(T)/CBSB7//B3LYP+Dispersion/CBSB7) and master equation calculations based on transition state theory (TST). Variational TST was used to compute both canonical (CVTST) and microcanonical (μVTST) rate constants for barrierless reactions. The title reaction starts with the reversible formation of a cyclic prereactive complex (PRC) that is bound by ∼11 kcal/mol and contains hydrogen bonds to both nitrogen and oxygen. The reaction path for the entrance channel was investigated by a series of constrained optimizations, which showed that the reaction is barrierless (i.e., no intrinsic energy barrier along the path). However, the variations in the potential energy, vibrational frequencies, and rotational constants reveal that the two hydrogen bonds are formed sequentially, producing two reaction flux bottlenecks (i.e., two transition states) along the reaction path, which were modeled using W. H. Miller's unified TST approach. The rate constant computed for the formation of the PRC is pressure-dependent and increases at lower temperatures. Under atmospheric conditions, the PRC dissociates rapidly and its lifetime is too short for it to undergo significant bimolecular reaction with other species. A small fraction isomerizes via a cyclic transition state and subsequent reactions lead to products normally expected from hydrogen abstraction reactions. The kinetics of the HO2 + CH2NH reaction system differs substantially from the analogous isoelectronic reaction systems involving C2H4 and CH2O, which have been the subjects of previous experimental and theoretical studies.

  5. Structure of RNA 3'-phosphate cyclase bound to substrate RNA.

    Science.gov (United States)

    Desai, Kevin K; Bingman, Craig A; Cheng, Chin L; Phillips, George N; Raines, Ronald T

    2014-10-01

    RNA 3'-phosphate cyclase (RtcA) catalyzes the ATP-dependent cyclization of a 3'-phosphate to form a 2',3'-cyclic phosphate at RNA termini. Cyclization proceeds through RtcA-AMP and RNA(3')pp(5')A covalent intermediates, which are analogous to intermediates formed during catalysis by the tRNA ligase RtcB. Here we present a crystal structure of Pyrococcus horikoshii RtcA in complex with a 3'-phosphate terminated RNA and adenosine in the AMP-binding pocket. Our data reveal that RtcA recognizes substrate RNA by ensuring that the terminal 3'-phosphate makes a large contribution to RNA binding. Furthermore, the RNA 3'-phosphate is poised for in-line attack on the P-N bond that links the phosphorous atom of AMP to N(ε) of His307. Thus, we provide the first insights into RNA 3'-phosphate termini recognition and the mechanism of 3'-phosphate activation by an Rtc enzyme.

  6. Metal-phosphate binders

    Science.gov (United States)

    Howe, Beth Ann [Lewistown, IL; Chaps-Cabrera, Jesus Guadalupe [Coahuila, MX

    2009-05-12

    A metal-phosphate binder is provided. The binder may include an aqueous phosphoric acid solution, a metal-cation donor including a metal other than aluminum, an aluminum-cation donor, and a non-carbohydrate electron donor.

  7. A Chemical Understanding of the Band Convergence in Thermoelectric CoSb 3 Skutterudites: Influence of Electron Population, Local Thermal Expansion, and Bonding Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Hanus, Riley; Guo, Xingyu; Tang, Yinglu; Li, Guodong; Snyder, G. Jeffrey; Zeier, Wolfgang G.

    2017-01-13

    N-Type skutterudites, such as YbxCo4Sb12, have recently been shown to exhibit high valley degeneracy with possible band convergence, explaining the excellent thermoelectric efficiency of these materials. Using a combined theoretical and experimental approach involving temperature-dependent synchrotron diffraction, molecular orbital diagrams, and computational studies, the chemical nature of critical features in the band structure is highlighted. We identify how n-type doping on the filler site induces structural changes that are observed in both the diffraction data and computational results. Additionally, we show how chemical n-type doping slightly alters the electronic band structure, moving the high-valley degeneracy secondary conduction band closer to the primary conduction band and thus inducing band convergence.

  8. Mechanical Behavior and Thermal Stability of Acid-Base Phosphate Cements and Composites Fabricated at Ambient Temperature

    Science.gov (United States)

    Colorado Lopera, Henry Alonso

    This dissertation presents the study of the mechanical behavior and thermal stability of acid-base phosphate cements (PCs) and composites fabricated at ambient temperature. These materials are also known as chemically bonded phosphate ceramics (CBPCs). Among other advantages of using PCs when compared with traditional cements are the better mechanical properties (compressive and flexural strength), lower density, ultra-fast (controllable) setting time, controllable pH, and an environmentally benign process. Several PCs based on wollastonite and calcium and alumino phosphates after thermal exposure up to 1000°C have been investigated. First, the thermo-mechanical and chemical stability of wollastonite-based PC (Wo-PC) exposed to temperatures up to 1000°C in air environment were studied. The effects of processing conditions on the curing and shrinkage of the wollastonite-based PC were studied. The chemical reactions and phase transformations during the fabrication and during the thermal exposure are analyzed in detail using scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermo-gravimetric analysis (TGA Then, the thermo-mechanical and chemical stability of glass, carbon and basalt fiber reinforced Wo-PC composites, were studied using SEM, XRD, TGA. The flexural strength and Weibull statistics were analyzed. A significant strength degradation in the composites were found after the thermal exposure at elevated temperatures due to the interdifusion and chemical reactions across the fibers and the matrix at temperatures over 600°C. To overcome this barrier, we have developed a new PC based on calcium and alumino-phosphates (Ca-Al PCs). The Ca-Al PCs were studied in detail using SEM, XRD, TGA, curing, shrinkage, Weibull statistics, and compression tests. Our study has confirmed that this new composite material is chemically and mechanically stable at temperatures up to 1000°C. Moreover, the compression strength increases after exposure to 1000

  9. Phosphate control in dialysis.

    Science.gov (United States)

    Cupisti, Adamasco; Gallieni, Maurizio; Rizzo, Maria Antonietta; Caria, Stefania; Meola, Mario; Bolasco, Piergiorgio

    2013-10-04

    Prevention and correction of hyperphosphatemia is a major goal of chronic kidney disease-mineral and bone disorder (CKD-MBD) management, achievable through avoidance of a positive phosphate balance. To this aim, optimal dialysis removal, careful use of phosphate binders, and dietary phosphate control are needed to optimize the control of phosphate balance in well-nourished patients on a standard three-times-a-week hemodialysis schedule. Using a mixed diffusive-convective hemodialysis tecniques, and increasing the number and/or the duration of dialysis tecniques are all measures able to enhance phosphorus (P) mass removal through dialysis. However, dialytic removal does not equal the high P intake linked to the high dietary protein requirement of dialysis patients; hence, the use of intestinal P binders is mandatory to reduce P net intestinal absorption. Unfortunately, even a large dose of P binders is able to bind approximately 200-300 mg of P on a daily basis, so it is evident that their efficacy is limited in the case of an uncontrolled dietary P load. Hence, limitation of dietary P intake is needed to reach the goal of neutral phosphate balance in dialysis, coupled to an adequate protein intake. To this aim, patients should be informed and educated to avoid foods that are naturally rich in phosphate and also processed food with P-containing preservatives. In addition, patients should preferentially choose food with a low P-to-protein ratio. For example, patients could choose egg white or protein from a vegetable source. Finally, boiling should be the preferred cooking procedure, because it induces food demineralization, including phosphate loss. The integrated approach outlined in this article should be actively adapted as a therapeutic alliance by clinicians, dieticians, and patients for an effective control of phosphate balance in dialysis patients.

  10. Effect of substituents on the strength of N-X (X = H, F, and Cl) bond dissociation energies: a high-level quantum chemical study.

    Science.gov (United States)

    O'Reilly, Robert J; Karton, Amir; Radom, Leo

    2011-06-02

    The effect of substituents on the strength of N-X (X = H, F, and Cl) bonds has been investigated using the high-level W2w thermochemical protocol. The substituents have been selected to be representative of the key functional groups that are likely to be of biological, synthetic, or industrial importance for these systems. We interpreted the effects through the calculation of relative N-X bond dissociation energies (BDE) or radical stabilization energies (RSE(NX)). The BDE and RSE(NX) values depend on stabilizing/destabilizing effects in both the reactant molecule and the product radical of the dissociation reactions. To assist us in the analysis of the substituent effects, a number of additional thermochemical quantities have been introduced, including molecule stabilization energies (MSE(NX)). We find that the RSE(NH) values are (a) increased by electron-donating alkyl substituents or the vinyl substituent, (b) increased in imines, and (c) decreased by electron-withdrawing substituents such as CF(3) and carbonyl moieties or through protonation. A different picture emerges when considering the RSE(NF) and RSE(NCl) values because of the electronegativities of the halogen atoms. The RSE(NX)s differ from the RSE(NH) values by an amount related to the stabilization of the N-halogenated molecules and given by MSE(NX). We find that substituents that stabilize/destabilize the radicals also tend to stabilize/destabilize the N-halogenated molecules. As a result, N-F- and N-Cl-containing molecules that include alkyl substituents or correspond to imines are generally associated with RSE(NF) and RSE(NCl) values that are less positive or more negative than the corresponding RSE(NH). In contrast, N-F- and N-Cl-containing molecules that include electron-withdrawing substituents or are protonated are generally associated with RSE(NF) and RSE(NCl) values that are more positive or less negative than the corresponding RSE(NH).

  11. Hydrogen bonding in tight environments

    DEFF Research Database (Denmark)

    Pirrotta, Alessandro; Solomon, Gemma C.; Franco, Ignacio

    2016-01-01

    The single-molecule force spectroscopy of a prototypical class of hydrogen-bonded complexes is computationally investigated. The complexes consist of derivatives of a barbituric acid and a Hamilton receptor that can form up to six simultaneous hydrogen bonds. The force-extension (F-L) isotherms...... of the host-guest complexes are simulated using classical molecular dynamics and the MM3 force field, for which a refined set of hydrogen bond parameters was developed from MP2 ab initio computations. The F-L curves exhibit peaks that signal conformational changes during elongation, the most prominent...... of which is in the 60-180 pN range and corresponds to the force required to break the hydrogen bonds. These peaks in the F-L curves are shown to be sensitive to relatively small changes in the chemical structure of the host molecule. Thermodynamic insights into the supramolecular assembly were obtained...

  12. Mixed zirconia calcium phosphate coatings for dental implants: Tailoring coating stability and bioactivity potential

    Energy Technology Data Exchange (ETDEWEB)

    Pardun, Karoline [University of Bremen, Advanced Ceramics, Am Biologischen Garten 2, 28359 Bremen (Germany); Treccani, Laura, E-mail: treccani@uni-bremen.de [University of Bremen, Advanced Ceramics, Am Biologischen Garten 2, 28359 Bremen (Germany); Volkmann, Eike [University of Bremen, Advanced Ceramics, Am Biologischen Garten 2, 28359 Bremen (Germany); Streckbein, Philipp [University Hospital, Justus-Liebig-University Giessen, Department of Cranio-Maxillo-Facial Surgery, Klinikstrasse 33, 35385 Giessen (Germany); Heiss, Christian [University Hospital of Giessen-Marburg, Department of Trauma Surgery, Rudolf-Buchheim-Strasse 7, 35385 Giessen, Germany, (Germany); Laboratory of Experimental Surgery, Kerkraderstrasse 9, 35392 Giessen (Germany); Destri, Giovanni Li; Marletta, Giovanni [Laboratory for Molecular Surfaces and Nanotechnology (LAMSUN), Department of Chemistry, University of Catania and CSGI, Viale A. Doria 6, 95125 Catania (Italy); Rezwan, Kurosch [University of Bremen, Advanced Ceramics, Am Biologischen Garten 2, 28359 Bremen (Germany)

    2015-03-01

    Enhanced coating stability and adhesion are essential for long-term success of orthopedic and dental implants. In this study, the effect of coating composition on mechanical, physico-chemical and biological properties of coated zirconia specimens is investigated. Zirconia discs and dental screw implants are coated using the wet powder spraying (WPS) technique. The coatings are obtained by mixing yttria-stabilized zirconia (TZ) and hydroxyapatite (HA) in various ratios while a pure HA coating served as reference material. Scanning electron microscopy (SEM) and optical profilometer analysis confirm a similar coating morphology and roughness for all studied coatings, whereas the coating stability can be tailored with composition and is probed by insertion and dissections experiments in bovine bone with coated zirconia screw implants. An increasing content of calcium phosphate (CP) resulted in a decrease of mechanical and chemical stability, while the bioactivity increased in simulated body fluid (SBF). In vitro experiments with human osteoblast cells (HOB) revealed that the cells grew well on all samples but are affected by dissolution behavior of the studied coatings. This work demonstrates the overall good mechanical strength, the excellent interfacial bonding and the bioactivity potential of coatings with higher TZ contents, which provide a highly interesting coating for dental implants. - Highlights: • Different ratios of zirconia (TZ) and calcium phosphate (CP) were deposited on zirconia substrates. • Enhancement of TZ content in mixed coatings increased coating stability. • Enhancement of CP content in mixed coatings increased bioactivity. • All tested coating compositions were non-toxic.

  13. Dicalcium phosphate cements: brushite and monetite.

    Science.gov (United States)

    Tamimi, Faleh; Sheikh, Zeeshan; Barralet, Jake

    2012-02-01

    Dicalcium phosphate cements were developed two decades ago and ever since there has been a substantial growth in research into improving their properties in order to satisfy the requirements needed for several clinical applications. The present paper presents an overview of the rapidly expanding research field of the two main dicalcium phosphate bioceramics: brushite and monetite. This review begins with a summary of all the different formulae developed to prepare dicalcium phosphate cements, and their setting reaction, in order to set the scene for the key cement physical and chemical properties, such as compressive and tensile strength, cohesion, injectability and shelf-life. We address the issue of brushite conversion into either monetite or apatite. Moreover, we discuss the in vivo behavior of the cements, including their ability to promote bone formation, biodegradation and potential clinical applications in drug delivery, orthopedics, craniofacial surgery, cancer therapy and biosensors.

  14. Density functional study of electronic, charge density, and chemical bonding properties of 9-methyl-3-Thiophen-2-YI-Thieno [3,2-e] [1, 2, 4] Thriazolo [4,3-c] pyrimidine-8-Carboxylic acid ethyl ester crystals

    Energy Technology Data Exchange (ETDEWEB)

    Reshak, A.H., E-mail: maalidph@yahoo.co.uk [New Technologies – Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Kamarudin, H. [Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Alahmed, Z.A. [Department of Physics and Astronomy, King Saud University, Riyadh 11451 (Saudi Arabia); Auluck, S. [CSIR-National Physical Laboratory, Dr. K S Krishnan Marg, New Delhi 110012 (India); Chyský, Jan [Department of Instrumentation and Control Engineering, Faculty of Mechanical Engineering, CTU in Prague, Technicka 4, 166 07 Prague 6 (Czech Republic)

    2014-06-01

    A comprehensive theoretical density functional investigation of the electronic crystal structure, chemical bonding, and the electron charge densities of 9-Methyl-3-Thiophen-2-YI-Thieno [3, 2-e] [1, 2, 4] Thriazolo [4,3-c] Pyrimidine-8-Carboxylic Acid Ethyl Ester (C{sub 15}H{sub 12}N{sub 4}O{sub 2}S{sub 2}) is performed. The density of states at Fermi level equal to 5.50 (3.45) states/Ry cell, and the calculated bare electronic specific heat coefficient is found to be 0.95 (0.59) mJ/mole-K{sup 2} for the local density approximation (Engel–Vosko generalized gradient approximation). The electronic charge density space distribution contours in (1 0 0) and (1 1 0) planes were calculated. We find that there are two independent molecules (A and B) in the asymmetric unit exhibit intramolecular C–H…O, C–H…N interactions. This intramolecular interaction is different in molecules A and B, where A molecule show C–H…O interaction while B molecule exhibit C–H…N interaction. We should emphasis that there is π–π interaction between the pyrimidine rings of the two neighbors B molecules gives extra strengths and stabilizations to the superamolecular structure. The calculated distance between the two neighbors pyrimidine rings found to be 3.345 Å, in good agreement with the measured one (3.424(1) Å). - Highlights: • Electronic structure, chemical bonding, and electron charge density were studied. • Density of states at Fermi level is 5.50 (3.45) states/Ry cell, for LDA (EVGGA). • Bare electronic specific heat coefficient is 0.95 (0.59) mJ/mole-K{sup 2} for LDA(EVGGA). • There are two independent molecules (A and B) in the asymmetric unit.

  15. Thermoelectric, electronic, optical and chemical bonding properties of Ba{sub 2}PrRuO{sub 6}: At temperature 7 K and 150 K

    Energy Technology Data Exchange (ETDEWEB)

    Reshak, A.H. [New Technologies-Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, Kangar, Perlis 01007 Malaysia (Malaysia); Khan, Wilayat, E-mail: walayat76@gmail.com [New Technologies-Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic)

    2015-01-15

    Highlights: • DFT-FPLAPW method used for calculating the electronic structure. • The Fermi surface of BPRO (7 K and 150 K) is also calculated. • The complex dielectric function has been calculated. • Thermoelectric properties were also calculated using BoltzTraP code. • Power factor shows that both compounds are good thermoelectric materials at 600 K. - Abstract: We present first principles calculations of the band structure, density of states, electronic charge density, Fermi surface and optical properties of Ba{sub 2}PrRuO{sub 6} single crystals at two different temperatures. The atomic positions were optimized by minimizing the forces acting on the atoms. We have employed the full potential linear augmented plane wave method within local density approximation, generalized gradient approximation and Engel–Vosko generalized gradient approximation to treat the exchange correlation potential. The calculation shows that the compound is superconductor with strong hybridization near the Fermi energy level. Fermi surface is composed of two sheets. The calculated electronic specific heat capacities indicate, very close agreement with the experimental one. The bonding features of the compounds are analyzed using the electronic charge density in the (1 0 0) and (0–10) crystallographic planes. The dispersion of the optical constants was calculated and discussed. The thermoelectric properties are also calculated using the BoltzTrap code.

  16. Aluminium phosphate sulphate minerals (APS) associated with proterozoic unconformity-type uranium deposits: crystal-chemical characterisation and petrogenetic significance; Les sulfates phosphates d'aluminium hydrates (APS) dans l'environnement des gisements d'uranium associes a une discordance proterozoique: caracterisation cristallochimique et signification petrogenetique

    Energy Technology Data Exchange (ETDEWEB)

    Gaboreau, St

    2005-07-01

    Aluminium phosphate sulfate minerals (APS) are particularly widespread and spatially associated with hydrothermal clay alteration in both the East Alligator River Uranium Field (Northern Territory, Australia) and the Athabasca basin (Saskatchewan, Canada), in the environment of proterozoic unconformity-related uranium deposits (URUD). The purpose of this study is both: 1) to characterize the nature and the origin of the APS minerals on both sides of the middle proterozoic unconformity between the overlying sandstones and the underlying metamorphic basement rocks that host the uranium ore bodies, 2) to improve our knowledge on the suitability of these minerals to indicate the paleo-conditions (redox, pH) at which the alteration processes relative to the uranium deposition operated. The APS minerals result from the interaction of oxidising and relatively acidic fluids with aluminous host rocks enriched in monazite. Several APS-bearing clay assemblages and APS crystal-chemistry have also been distinguished as a function of the distance from the uranium ore bodies or from the structural discontinuities which drained the hydrothermal solutions during the mineralisation event. One of the main results of this study is that the index mineral assemblages, used in the recent literature to describe the alteration zones around the uranium ore bodies, can be theoretically predicted by a set of thermodynamic calculations which simulate different steps of fluid-rock interaction processes related to a downward penetrating of hyper-saline, oxidizing and acidic diagenetic fluids through the lower sandstone units of the basins and then into the metamorphic basement rocks. The above considerations and the fact that APS with different crystal-chemical compositions crystallized in a range of fO{sub 2} and pH at which uranium can either be transported in solution or precipitated as uraninite in the host-rocks make these minerals not only good markers of the degree of alteration of the

  17. On double bonds in fullerenes

    Directory of Open Access Journals (Sweden)

    Stepenshchikov D. G.

    2016-03-01

    Full Text Available Various distributions of double carbon bonds in the fullerenes have been considered in the paper from the point that they are absent in the pentagonal rings. The appropriate classification of the fullerenes has been built. The results may be used when modeling the fullerenes of a given topology and calculating their physical-chemical properties

  18. Solvothermal synthesis of strontium phosphate chloride nanowire

    Science.gov (United States)

    Lam, W. M.; Wong, C. T.; Li, Z. Y.; Luk, K. D. K.; Chan, W. K.; Yang, C.; Chiu, K. Y.; Xu, B.; Lu, W. W.

    2007-08-01

    Strontium phosphate chloride nanowire was synthesized via a solvothermal treatment of strontium tri-polyphosphate and Collin salt in 1,4-dioxane at 150 °C. The effects of 1,4-dioxane concentration on particle morphology, crystallinity and phase purity were investigated in this study. The specimen morphology was analyzed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). When the concentration of 1,4-dioxane was below 10%, micron-sized whisker was the dominant form. At 20-25% concentration of 1,4-dioxane, strontium phosphate chloride single-crystalline nanowire was 31±12 nm in diameter and 1.43±0.6 μm in length with an aspect ratio of 52.28±29.41. X-ray diffraction (XRD) pattern of this nanowire matched with that of strontium phosphate chloride (JCPDS #083-0973). When 1,4-dioxane concentration exceeded 25%, nanorod aggregate was the dominant form instead of nanowire. At 20-25% 1,4-dioxane concentration suitable strontium concentration combine with high chemical potential environment favors the formation of nanowires. By adding 1,4-dioxane impure phase such as β-strontium hydrogen phosphate, nanorod formation was suppressed. This method provides an efficient way to synthesize high aspect ratio strontium phosphate chloride nanowire. It has potential bioactive nanocomposite, high mechanical performance bioactive bone cement filler and fluorescent material applications.

  19. Sodium ascorbyl phosphate in topical microemulsions.

    Science.gov (United States)

    Spiclin, Polona; Homar, Miha; Zupancic-Valant, Andreja; Gasperlin, Mirjana

    2003-04-30

    Sodium ascorbyl phosphate is a hydrophilic derivative of ascorbic acid, which has improved stability arising from its chemical structure. It is used in cosmetic and pharmaceutical preparations since it has many favorable effects in the skin, the most important being antioxidant action. In order to achieve this, it has to be converted into free ascorbic acid by enzymatic degradation in the skin. In the present work, o/w and w/o microemulsions composed of the same ingredients, were selected as carrier systems for topical delivery of sodium ascorbyl phosphate. We showed that sodium ascorbyl phosphate was stable in both types of microemulsion with no significant influence of its location in the carrier system. To obtain liquid microemulsions appropriate for topical application, their viscosity was increased by adding thickening agents. On the basis of rheological characterization, 4.00% (m/m) colloidal silica was chosen as a suitable thickening agent for w/o microemulsions and 0.50% (m/m) xanthan gum for the o/w type. The presence of thickening agent and the location of sodium ascorbyl phosphate in the microemulsion influenced the in vitro drug release profiles. When incorporated in the internal aqueous phase, sustained release profiles were observed. This study confirmed microemulsions as suitable carrier systems for topical application of sodium ascorbyl phosphate.

  20. The effects of inorganic phosphate and arsenate on both passive muscle visco-elasticity and maximum Ca2+ activated tension in chemically skinned rat fast and slow twitch muscle fibres.

    Science.gov (United States)

    Mutungi, Gabriel

    2003-01-01

    The effects of adding either 25 mM inorganic phosphate (Pi) or its structural analogue arsenate (ASi) on both the maximum Ca2+ activated tension (Po) and passive muscle visco-elasticity (P2 tension) were investigated at 10 degrees C, using segments of single, chemically skinned rat muscle fibres. Whilst the results confirmed some previous findings on the effects of Pi on Po, they also showed that the addition of 25 mM ASi led to a large (approximately 50%) but completely reversible depression of Po in both the fast and slow twitch rat muscle fibres. Moreover, the depression of Po by ASi was greater at low than at high pH values. Examined in the presence of Dextran T-500, the passive tension and sarcomere length responses to a ramp stretch were found to be qualitatively and quantitatively similar to those previously reported in intact rat muscle fibres. Thus, the tension response to a ramp stretch, in the presence and absence of either 25 mM Pi or ASi, consisted of a viscous (P1), a visco-elastic (P2) and an elastic (P3) tension. However, the addition of either 25 mM Pi or ASi led to approximately 15-18% increase in the amplitude of the visco-elastic (P2) tension but had little or no effect on the amplitudes of the other two tension components (viscous, P1 and elastic, P3 tensions). Furthermore, neither compound significantly altered the relaxation rate of the passive muscle visco-elasticity (P2 tension). These results show that Po (arising from cycling cross-bridges) and passive muscle visco-elasticity (P2 tension) are affected differently by both Pi and ASi and suggest that they may not share a common structural basis. The possibility that passive muscle visco-elasticity (P2 tension) arises from the gap-(titin) filament (as suggested previously by Mutungi and Ranatunga, 1996b J Physiol 496: 827-837) and that Pi and ASi increase its amplitude by interacting with the PEVK region of the filament are discussed.

  1. Chemical conversion process of AZ91D magnesium alloy based on phosphate-permanganate electrolyte%AZ91D镁合金磷酸盐-高锰酸盐体系化学转化工艺

    Institute of Scientific and Technical Information of China (English)

    农登; 宋东福; 戚文军; 梁涛; 赵雅情

    2012-01-01

    通过正交试验研究了以磷酸盐-高锰酸盐为基础的镁合金无铬转化工艺,讨论了工艺参数对转化膜厚度及其有机涂层耐蚀的影响,并通过扫描电镜、能谱等方法分析了转化膜的微观形貌和化学成分.研究表明,当磷酸二氢铵为10~15 g/L、高锰酸钾为5~10g/L时,磷酸盐-高锰酸的最佳处理工艺为:ZnSO43 g/L,NaF 3 g/L,pH 3,温度45℃.转化液pH对膜层厚度及有机涂层的耐蚀性有显著的影响.在试验参数范围内,转化膜的厚度及后续有机涂层的耐蚀性能随pH的减小而大幅度提高.经该工艺处理后,后续有机涂层的耐蚀性能提高10倍以上.%A process for chromium-free conversion of magnesium alloys based on phosphate-permanganate electrolyte was studied by orthogonal test. The effects of process parameters on the thickness of conversion film and the corrosion resistance of organic coating on it were discussed. The microscopic morphology and chemical composition of the conversion film were analyzed by SEM and energy-dispersive spectroscopy. For an electrolyte containing NH4H2PO4 10-15 g/L and KMnO4 5-10g/L, the optimal process conditions are as follows: ZnSO4 3 g/L, NaF 3 g/L, temperature 45 °C, and pH 3. The thickness of conversion film and the corrosion resistance of subsequently prepared organic coating are greatly affected by the pH of electrolyte, since they are increased greatly with the decreasing of pH in the test range. The corrosion resistance of subsequent organic coating is improved by more than 10 times after treatment by the process.

  2. 新型钙镁磷酸复合材料理化机械性能的初步评价%Mechanical and chemical properties of novel calcium-magnesium phosphate cements

    Institute of Scientific and Technical Information of China (English)

    沈晴昳; 李恺; 李国强

    2016-01-01

    Objective To study the mechanical and chemical properties of novel calcium⁃magnesium phosphate cements( CMPCs) . Methods Components of the CMPCs were analyzed by XRD and SEM. The physicochemical properties of the CMPCs were investiga⁃ted, and the effects of different components on setting time, compressive strength, rate of degradation were studied. Results Accord⁃ing to the analysis of XRD and SEM, CMPCs were composed of Ca3( PO4 ) 2 , Mg3( PO4 ) 2 and HA, and a small amount of unreacted MgO was also observed. It showed that with the increasing amount the CMPCs exhibited shorter setting time and higher compressive strength than the CPC. In addition, CMPCs showed significantly improved degradability compared with the CPC in SBF. Conclusion CMPCs possess a significant clinical advantage over CPC, and it might have the value of in⁃depth study as dental restorative material.%目的:研究新型磷酸钙-磷酸镁水门汀( CMPCs)的理化机械性能。方法采用 X 射线衍射( XRD)、扫描电镜( SEM)分析主要物相组成,研究比较材料不同组成对固化时间、抗压强度、降解率的影响。结果 XRD、SEM 分析显示, CMPCs主要包含Ca3( PO4)2、Mg3( PO4)2、HA以及少量MgO。随着磷酸镁水门汀含量的增加,CMPCs的固化时间缩短,抗压强度提高,降解率升高。结论 CMPCs理化机械性能优良,作为齿科修复材料具有深入研究的价值。

  3. Hydrogen bond dynamics in bulk alcohols

    NARCIS (Netherlands)

    Shinokita, Keisuke; Cunha, Ana V.; Jansen, Thomas L. C.; Pshenichnikov, Maxim S.

    2015-01-01

    Hydrogen-bonded liquids play a significant role in numerous chemical and biological phenomena. In the past decade, impressive developments in multidimensional vibrational spectroscopy and combined molecular dynamics-quantum mechanical simulation have established many intriguing features of hydrogen

  4. Phosphate control in dialysis

    Directory of Open Access Journals (Sweden)

    Cupisti A

    2013-10-01

    Full Text Available Adamasco Cupisti,1 Maurizio Gallieni,2 Maria Antonietta Rizzo,2 Stefania Caria,3 Mario Meola,4 Piergiorgio Bolasco31Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy; 2Nephrology and Dialysis Unit, San Carlo Borromeo Hospital, Milan, Italy; 3Territorial Department of Nephrology and Dialysis, ASL Cagliari, Italy; 4Sant'Anna School of Advanced Studies, University of Pisa, Pisa, ItalyAbstract: Prevention and correction of hyperphosphatemia is a major goal of chronic kidney disease–mineral and bone disorder (CKD–MBD management, achievable through avoidance of a positive phosphate balance. To this aim, optimal dialysis removal, careful use of phosphate binders, and dietary phosphate control are needed to optimize the control of phosphate balance in well-nourished patients on a standard three-times-a-week hemodialysis schedule. Using a mixed diffusive–convective hemodialysis tecniques, and increasing the number and/or the duration of dialysis tecniques are all measures able to enhance phosphorus (P mass removal through dialysis. However, dialytic removal does not equal the high P intake linked to the high dietary protein requirement of dialysis patients; hence, the use of intestinal P binders is mandatory to reduce P net intestinal absorption. Unfortunately, even a large dose of P binders is able to bind approximately 200–300 mg of P on a daily basis, so it is evident that their efficacy is limited in the case of an uncontrolled dietary P load. Hence, limitation of dietary P intake is needed to reach the goal of neutral phosphate balance in dialysis, coupled to an adequate protein intake. To this aim, patients should be informed and educated to avoid foods that are naturally rich in phosphate and also processed food with P-containing preservatives. In addition, patients should preferentially choose food with a low P-to-protein ratio. For example, patients could choose egg white or protein from a vegetable source

  5. Chemically optimized antimyosin Fab conjugates with chelating polymers: importance of the nature of the protein-polymer single site covalent bond for biodistribution and infarction localization.

    Science.gov (United States)

    Trubetskoy, V S; Narula, J; Khaw, B A; Torchilin, V P

    1993-01-01

    Murine antimyosin Fab fragment was conjugated with 111In-labeled N-terminal-modified DTPA-polylysine using three bifunctional reagents: N-hydroxysuccinimide esters of 3-(2-pyridyldithio)propionic acid (SPDP conjugate), 4-(maleimidomethyl)cyclohexanecarboxylic acid (SMCC conjugate) and bromoacetic acid (BrAc conjugate) for potential localization of experimental myocardial infarction. Using various antibody preparations and a rabbit acute myocardial infarction model the following parameters were observed: (1) an in vitro antigen binding activity of SPDP conjugate = SMCC conjugate > BrAc conjugate, (2) a blood clearance rate of SPDP conjugate > BrAc conjugate > SMCC conjugate, (3) a liver and splenic accumulation of SPDP conjugate > BrAc conjugate > SMCC conjugate, and (4) the infarcted tissue activity showed an accumulation of SMCC conjugate > SPDP conjugate > BrAc conjugate. This study exemplifies the importance of rational chemical design of antimyosin Fab-chelating polymer conjugate for improved target tissue localization in vivo.

  6. In vitro and in vivo studies on the thin and defect-free calcium phosphate films formed by electron-beam evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D.H.; Kwon, S.H.; Hong, S.H.; Kim, H.E.; Lee, I.S. [Seoul National Univ. (Korea). School of Materials Science and Engineering; Jung, Y.C. [Yonsei Univ. (Korea). Coll. of Dentistry

    2001-07-01

    The thin and defect-free calcium phosphate film deposited to a thickness of 1 {mu}m by electron beam evaporation was characterized in vivo and in vitro. For the in vivo study, as-machined, as-blasted, and calcium phosphate coating on machined surface of commercially pure titanium screw implants were inserted in the rabbit tibiae. Twelve screws of each condition were implanted, and the total of 144 implants were evaluated. The various Ca/P ratios of calcium phosphate films were formed by e-beam evaporation without simultaneous Ar ion bombardment. The as-deposited films had the average bonding strengths of 64.8 MPa to metal implant and different dissolution rates with the Ca/P ratio. After a healing period of 12-week, at the day of sacrifice, the implants were unscrewed with a torque gauge instrument. The coated sample showed the highest removal torque in both normal and ovariectomized group indicating direct chemical bond with bone tissues. (orig.)

  7. DFT modeling of the electronic and magnetic structures and chemical bonding properties of intermetallic hydrides; Modelisation au sein de la DFT des proprietes des structures electronique et magnetique et de liaison chimique des Hydrures d'Intermetalliques

    Energy Technology Data Exchange (ETDEWEB)

    Al Alam, A.F.

    2009-06-15

    This thesis presents an ab initio study of several classes of intermetallics and their hydrides. These compounds are interesting from both a fundamental and an applied points of view. To achieve this aim two complementary methods, constructed within the DFT, were chosen: (i) pseudo potential based VASP for geometry optimization, structural investigations and electron localization mapping (ELF), and (ii) all-electrons ASW method for a detailed description of the electronic structure, chemical bonding properties following different schemes as well as quantities depending on core electrons such as the hyperfine field. A special interest is given with respect to the interplay between magneto-volume and chemical interactions (metal-H) effects within the following hydrided systems: binary Laves (e.g. ScFe{sub 2}) and Haucke (e.g. LaNi{sub 5}) phases on one hand, and ternary cerium based (e.g. CeRhSn) and uranium based (e.g. U{sub 2}Ni{sub 2}Sn) alloys on the other hand. (author)

  8. Synthesis of aryl phosphates based on pyrimidine and triazine scaffolds.

    Science.gov (United States)

    Courme, Caroline; Gresh, Nohad; Vidal, Michel; Lenoir, Christine; Garbay, Christiane; Florent, Jean-Claude; Bertounesque, Emmanuel

    2010-01-01

    The syntheses of the triazinyl-based bis-aryl phosphates 2 and 3, and of the aminopyrimidyl-based aryl phosphate 4 are described. Each compound contains a diaryl ether-phosphate structural motif. The synthetic route to bis-aryl phosphates 2 and 3 consisted in two nucleophilic substitution reactions with amines from cyanuric chloride, followed by a Suzuki coupling with the resulting 2,4-diamino-6-chloro-1,3,5-triazine derivative 12 to introduce the diaryl ether functionality. Aryl phosphate 4 was obtained via condensation of aryl guanidine 34 with aryloxyphenyl butenone 31. These de novo-designed aryl phosphates were evaluated as potential inhibitors of the Grb2-SH2 domain using an ELISA assay. The water-soluble sodium salt 26 of 3 gave an IC(50) value in the high micromolar range. Molecular modeling studies were subsequently performed upon modifying the 1,3,5-trisubstituted triazine scaffold of 3. Non-phosphate derivatives encompassing cyclopropane, pyrrole, keto-acid, and IZD fragments were thus step-wise designed and their Grb2-SH2 complexes were modeled by molecular dynamics. Some derivatives gave rise to an enriched pattern of H-bonds and cation-pi interactions with Grb2-SH2.

  9. Phosphate Mines, Jordan

    Science.gov (United States)

    2008-01-01

    Jordan's leading industry and export commodities are phosphate and potash, ranked in the top three in the world. These are used to make fertilizer. The Jordan Phosphate Mines Company is the sole producer, having started operations in 1935. In addition to mining activities, the company produces phosphoric acid (for fertilizers, detergents, pharmaceuticals), diammonium phosphate (for fertilizer), sulphuric acid (many uses), and aluminum fluoride (a catalyst to make aluminum and magnesium). The image covers an area of 27.5 x 49.4 km, was acquired on September 17, 2005, and is located near 30.8 degrees north latitude, 36.1 degrees east longitude. The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  10. Surface chemical bonds, surface-enhanced Raman scattering, and dielectric constant of SiO2 nanospheres in-situ decorated with Ag-nanoparticles by electron-irradiation

    Science.gov (United States)

    Phatangare, A. B.; Dhole, S. D.; Dahiwale, S. S.; Mathe, V. L.; Bhoraskar, S. V.; Late, D. J.; Bhoraskar, V. N.

    2016-12-01

    Nanostructures of dielectric materials decorated with metal nanoparticles are of great scientific interest; however, the involved synthesis methods are complicated and require multistep chemical processing, including functionalization of the dielectric surfaces. In the present work, without chemical processes, silver nanoparticles of average sizes in the range of 11 to 15 nm were in-situ synthesized and decorated on SiO2 nanospheres in a single step process by irradiating a solution (AgNO3-polyvinylpyrrolidone (PVP)-SiO2 nanospheres) with 6 MeV electrons at 1.5 × 1015 e-/cm2, 3.0 × 1015 e-/cm2, and 4.5 × 1015 e-/cm2 fluences. The electron irradiated solutions were characterized with different surface and other techniques. The results revealed that the SiO2 nanospheres were uniformly decorated with Ag nanoparticles, and the prominent chemical bonds involved were Ag-O, Si-O-Ag, and Si-Ag. Moreover, the sizes and the decoration density of Ag nanoparticles could be tailored by varying electron fluence. The Surface-enhanced Raman scattering (SERS) of 4-aminothiophenol (4-ATP) solutions was studied using substrates in the form of thin coatings of the solutions of Ag-decorated SiO2 nanospheres. The appearance of the characteristic SERS peaks of both 4-ATP and 4, 4'-dimercaptoazobenzene (4, 4'-DMAB) in Raman spectra confirmed the conversion of a fraction of 4-ATP into 4, 4'-DMAB in the presence of Ag nanoparticles. Composites in the form of thin films were synthesized from the mixture solutions of PVP and Ag-decorated SiO2 nanospheres. The dielectric constant of each thin film was higher as compared to polymers, and could be tailored by varying electron fluence used for decorating Ag nanoparticles.

  11. New insights into the interactions between cork chemical components and pesticides. The contribution of π-π interactions, hydrogen bonding and hydrophobic effect.

    Science.gov (United States)

    Olivella, M À; Bazzicalupi, C; Bianchi, A; Fiol, N; Villaescusa, I

    2015-01-01

    The role of chemical components of cork in the sorption of several pesticides has been investigated. For this purpose raw cork and three cork extracted fractions (i.e. cork free of aliphatic extractives, cork free of all extractives and cork free of all extractives and suberin) were used as sorbent of three ionic pesticides (propazine, 2,4-dichlorophenoxy acetic acid (2,4-D) and alachlor) and five non-ionic pesticides (chlorpyrifos, isoproturon, metamitron, methomyl and oxamyl) with a logKow within the range -0.47 to 4.92. The effect of cations on the ionic pesticides, propazine and 2,4-D sorption was also analyzed. Results indicated that the highest yields were obtained for chlorpyrifos and alachlor sorption onto raw cork (>55%). After removal of aliphatic extractives sorption of all pesticides increased that ranged from 3% for propazine to 31% for alachlor. In contrast, removal of phenolic extractives caused a sorption decrease. Low sorption yields were obtained for hydrophobic pesticides such as metamitron, oxamyl and methomyl (cork fractions and extremely low when using raw cork (cork toward aromatic pesticides. Results presented in this paper gain insights into the cork affinities for pesticides and the interactions involved in the sorption process and also enables to envisage sorption affinity of cork for other organic pollutants.

  12. Can the hydrophilicity of functional monomers affect chemical interaction?

    Science.gov (United States)

    Feitosa, V P; Ogliari, F A; Van Meerbeek, B; Watson, T F; Yoshihara, K; Ogliari, A O; Sinhoreti, M A; Correr, A B; Cama, G; Sauro, S

    2014-02-01

    The number of carbon atoms and/or ester/polyether groups in spacer chains may influence the interaction of functional monomers with calcium and dentin. The present study assessed the chemical interaction and bond strength of 5 standard-synthesized phosphoric-acid ester functional monomers with different spacer chain characteristics, by atomic absorption spectroscopy (AAS), ATR-FTIR, thin-film x-ray diffraction (TF-XRD), scanning electron microscopy (SEM), and microtensile bond strength (μTBS). The tested functional monomers were 2-MEP (two-carbon spacer chain), 10-MDP (10-carbon), 12-MDDP (12-carbon), MTEP (more hydrophilic polyether spacer chain), and CAP-P (intermediate hydrophilicity ester spacer). The intensity of monomer-calcium salt formation measured by AAS differed in the order of 12-MDDP=10-MDP>CAP-P>MTEP>2-MEP. FTIR and SEM analyses of monomer-treated dentin surfaces showed resistance to rinsing for all monomer-dentin bonds, except with 2-MEP. TF-XRD confirmed the weaker interaction of 2-MEP. Highest µTBS was observed for 12-MDDP and 10-MDP. A shorter spacer chain (2-MEP) of phosphate functional monomers induced formation of unstable monomer-calcium salts, and lower chemical interaction and dentin bond strength. The presence of ester or ether groups within longer spacer carbon chains (CAP-P and MTEP) may affect the hydrophilicity, μTBS, and also the formation of monomer-calcium salts.

  13. DICOR surface treatments for enhanced bonding.

    Science.gov (United States)

    Bailey, L F; Bennett, R J

    1988-06-01

    Treatments for preparing castable ceramic surfaces for enhanced bonding to specially formulated resin-based cements were examined. An ammonium bifluoride etch combined with gamma-methacryloxypropyl-trimethoxysilane produced shear bond strengths higher than when an ammonium bifluoride treatment was used alone. The method of curing the silane was highly significant in the contribution to the cement/substrate bond strength, with the heat-cure producing the highest values. Long-term water storage tests indicated that the cement bond with etch plus silane-treated castable ceramic surfaces (whether heat or chemically cured silane was used) demonstrated no significant decrease in strength after a one-year period.

  14. Primary retention following nuclear recoil in β-decay: Proposed synthesis of a metastable rare gas oxide ((38)ArO4) from ((38)ClO4(-)) and the evolution of chemical bonding over the nuclear transmutation reaction path.

    Science.gov (United States)

    Timm, Matthew J; Matta, Chérif F

    2014-12-01

    Argon tetroxide (ArO4) is the last member of the N=50 e(-) isoelectronic and isosteric series of ions: SiO4(4-), PO4(3-), SO4(2-), and ClO4(-). A high level computational study demonstrated that while ArO4 is kinetically stable it has a considerable positive enthalpy of formation (of ~298kcal/mol) (Lindh et al., 1999. J. Phys. Chem. A 103, pp. 8295-8302) confirming earlier predictions by Pyykkö (1990. Phys. Scr. 33, pp. 52-53). ArO4 can be expected to be difficult to synthesize by traditional chemistry due to its metastability and has not yet been synthesized at the time of writing. A computational investigation of the changes in the chemical bonding of chlorate (ClO4(-)) when the central chlorine atom undergoes a nuclear transmutation from the unstable artificial chlorine isotope (38)Cl to the stable rare argon isotope (38)Ar through β-decay, hence potentially leading to the formation of ArO4, is reported. A mathematical model is presented that allows for the prediction of yields following the recoil of a nucleus upon ejecting a β-electron. It is demonstrated that below a critical angle between the ejected β-electron and that of the accompanying antineutrino their respective linear momentums can cancel to such an extent as imparting a recoil to the daughter atom insufficient for breaking the Ar-O bond. As a result, a primary retention yield of ~1% of ArO4 is predicted following the nuclear disintegration. The study is conducted at the quadratic configuration interaction with single and double excitations [QCISD/6-311+G(3df)] level of theory followed by an analysis of the electron density by the quantum theory of atoms in molecules (QTAIM). Crossed potential energy surfaces (PES) were used to construct a PES from the metastable ArO4 ground singlet state to the Ar-O bond dissociation product ArO3+O((3)P) from which the predicted barrier to dissociation is ca. 22kcal/mol and the exothermic reaction energy is ca. 28kcal/mol [(U)MP2/6-311+G(d)].

  15. Structural, spectroscopic, and multiconfigurational quantum chemical investigations of the electron-rich metal-metal triple-bonded Tc(2)X(4)(PMe(3))(4) (X = Cl, Br) complexes.

    Science.gov (United States)

    Poineau, Frederic; Forster, Paul M; Todorova, Tanya K; Gagliardi, Laura; Sattelberger, Alfred P; Czerwinski, Kenneth R

    2010-07-19

    The compounds Tc(2)Cl(4)(PMe(3))(4) and Tc(2)Br(4)(PMe(3))(4) were formed from the reaction between (n-Bu(4)N)(2)Tc(2)X(8) (X = Cl, Br) and trimethylphosphine. The Tc(II) dinuclear species were characterized by single-crystal XRD, UV-visible spectroscopy, and cyclic voltammetry techniques, and the results are compared to those obtained from density functional theory and multiconfigurational (CASSCF/CASPT2) quantum chemical studies. The compound Tc(2)Cl(4)(PMe(3))(4) crystallizes in the monoclinic space group C2/c [a = 17.9995(9) A, b = 9.1821(5) A, c = 17.0090(9) A, beta = 115.4530(10) degrees ] and is isostructural to M(2)Cl(4)(PMe(3))(4) (M = Re, Mo, W) and to Tc(2)Br(4)(PMe(3))(4). The metal-metal distance (2.1318(2) A) is similar to the one found in Tc(2)Br(4)(PMe(3))(4) (2.1316(5) A). The calculated molecular structures of the ground states are in excellent agreement with the structures determined experimentally. Calculations of effective bond orders for Tc(2)X(8)(2-) and Tc(2)X(4)(PMe(3))(4) (X = Cl, Br) indicate stronger pi bonds in the Tc(2)(4+) core than in Tc(2)(6+) core. The electronic spectra were recorded in benzene and show a series of low intensity bands in the range 10 000-26 000 cm(-1). Assignment of the bands as well as computing their excitation energies and intensities were performed at both TD-DFT and CASSCF/CASPT2 levels of theory. Calculations predict that the lowest energy band corresponds to the delta* --> sigma* transition, the difference between calculated and experimental values being 228 cm(-1) for X = Cl and 866 cm(-1) for X = Br. The next bands are attributed to delta* --> pi*, delta --> sigma*, and delta --> pi* transitions. The cyclic voltammograms exhibit two reversible waves and indicate that Tc(2)Br(4)(PMe(3))(4) exhibits more positive oxidation potentials than Tc(2)Cl(4)(PMe(3))(4.) This phenomenon is discussed and ascribed to stronger metal (d) to halide (d) back bonding in the bromo complex. Further analysis indicates that Tc

  16. Cross Shear Roll Bonding

    DEFF Research Database (Denmark)

    Bay, Niels; Bjerregaard, Henrik; Petersen, Søren. B;

    1994-01-01

    The present paper describes an investigation of roll bonding an AlZn alloy to mild steel. Application of cross shear roll bonding, where the two equal sized rolls run with different peripheral speed, is shown to give better bond strength than conventional roll bonding. Improvements of up to 20......-23% in bond strength are found and full bond strength is obtained at a reduction of 50% whereas 65% is required in case of conventional roll bonding. Pseudo cross shear roll bonding, where the cross shear effect is obtained by running two equal sized rolls with different speed, gives the same results....

  17. Reaction Mechanisms of Magnesium Potassium Phosphate Cement and its Application

    Science.gov (United States)

    Qiao, Fei

    Magnesium potassium phosphate cement (MKPC) is a kind of cementitious binder in which the chemical bond is formed via a heterogeneous acid-base reaction between dead burned magnesia powder and potassium phosphate solution at room temperature. Small amount of boron compounds can be incorporated in the cement as a setting retarder. The final reaction product of MgO-KH2PO4-H 2O ternary system is identified as magnesium potassium phosphate hexahydrate, MgKPO4·6H2O. However, the mechanisms and procedures through which this crystalline product is formed and the conditions under which the crystallization process would be influenced are not yet clear. Understanding of the reaction mechanism of the system is helpful for developing new methodologies to control the rapid reaction process and furthermore, to adjust the phase assemblage of the binder, and to enhance the macroscopic properties. This study is mainly focused on the examination of the reaction mechanism of MKPC. In addition, the formulation optimization, microstructure characterization and field application in rapid repair are also systematically studied. The chemical reactions between magnesia and potassium dihydrogen phosphate are essentially an acid-base reaction with strong heat release, the pH and temperature variation throughout the reaction process could provide useful information to disclose the different stages in the reaction. However, it would be very difficult to conduct such tests on the cement paste due to the limited water content and fast setting. In the current research, the reaction mechanism of MKPC is investigated on the diluted MKPC system through monitoring the pH and temperature development, identification of the solid phase formed, and measurement of the ionic concentration of the solution. The reaction process can be explained as follows: when magnesia and potassium phosphate powder are mixed with water, phosphate is readily dissolved, which is instantly followed by the dissociation of

  18. Fusion bonding of silicon nitride surfaces

    DEFF Research Database (Denmark)

    Reck, Kasper; Østergaard, Christian; Thomsen, Erik Vilain

    2011-01-01

    While silicon nitride surfaces are widely used in many micro electrical mechanical system devices, e.g. for chemical passivation, electrical isolation or environmental protection, studies on fusion bonding of two silicon nitride surfaces (Si3N4–Si3N4 bonding) are very few and highly application...... specific. Often fusion bonding of silicon nitride surfaces to silicon or silicon dioxide to silicon surfaces is preferred, though Si3N4–Si3N4 bonding is indeed possible and practical for many devices as will be shown in this paper. We present an overview of existing knowledge on Si3N4–Si3N4 bonding and new...... results on bonding of thin and thick Si3N4 layers. The new results include high temperature bonding without any pretreatment, along with improved bonding ability achieved by thermal oxidation and chemical pretreatment. The bonded wafers include both unprocessed and processed wafers with a total silicon...

  19. Iron phosphate materials as cathodes for lithium batteries

    CERN Document Server

    Prosini, Pier Paolo

    2011-01-01

    ""Iron Phosphate Materials as Cathodes for Lithium Batteries"" describes the synthesis and the chemical-physical characteristics of iron phosphates, and presents methods of making LiFePO4 a suitable cathode material for lithium-ion batteries. The author studies carbon's ability to increase conductivity and to decrease material grain size, as well as investigating the electrochemical behaviour of the materials obtained. ""Iron Phosphate Materials as Cathodes for Lithium Batteries"" also proposes a model to explain lithium insertion/extraction in LiFePO4 and to predict voltage profiles at variou

  20. Glucose-6-phosphate dehydrogenase deficiency

    Science.gov (United States)

    ... medlineplus.gov/ency/article/000528.htm Glucose-6-phosphate dehydrogenase deficiency To use the sharing features on this page, please enable JavaScript. Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a condition in which ...

  1. Research on Uncrystallized Phosphating Film

    Institute of Scientific and Technical Information of China (English)

    TANG En-jun; XING Ze-kuan

    2004-01-01

    This article excogitated a kind of uncrystallized phosphating film bears wearing capacity goodly by adding Ca2 + in normal phosphating solution. This technology is very useful to protect steel parts working in oil from abrasion.

  2. Bypassing the Pentose Phosphate Pathway: Towards Modular Utilization of Xylose

    OpenAIRE

    Kulika Chomvong; Stefan Bauer; Daniel I Benjamin; Xin Li; Daniel K Nomura; Cate, Jamie H. D.

    2016-01-01

    The efficient use of hemicellulose in the plant cell wall is critical for the economic conversion of plant biomass to renewable fuels and chemicals. Previously, the yeast Saccharomyces cerevisiae has been engineered to convert the hemicellulose-derived pentose sugars xylose and arabinose to d-xylulose-5-phosphate for conversion via the pentose phosphate pathway (PPP). However, efficient pentose utilization requires PPP optimization and may interfere with its roles in NADPH and pentose product...

  3. Thermoelectric, band structure, chemical bonding and dispersion of optical constants of new metal chalcogenides Ba{sub 4}CuGa{sub 5}Q{sub 12} (Q=S, Se)

    Energy Technology Data Exchange (ETDEWEB)

    Reshak, A.H. [New Technologies – Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Azam, Sikander, E-mail: sikander.physicst@gmail.com [New Technologies – Research Center, University of West Bohemia, Univerzitni 8, 306 14 Pilsen (Czech Republic)

    2014-08-01

    The electronic structure and dispersion of optical constants of the Ba{sub 4}CuGa{sub 5}S{sub 12} and Ba{sub 4}CuGa{sub 5}Se{sub 12} compounds were calculated by the first-principles full-potential linearized augmented plane wave (FPLAPW) method. We employed the local density approximation (LDA), generalized gradient approximation (GGA) and Engel–Vosko GGA (EVGGA) to calculate the electronic structures, Fermi surface, thermoelectric, chemical bonding and dispersion of optical constants of these compounds. By investigating the influence of replacing S by Se, it has been found that the charge density around ‘Ga’ is greater in Ba{sub 4}CuGa{sub 5}Se{sub 12} than Ba{sub 4}CuGa{sub 5}S{sub 12}. Fermi surface of Ba{sub 4}CuGa{sub 5}S{sub 12} consists of an electronic sheet only because there is no empty region while Ba{sub 4}CuGa{sub 5}Se{sub 12} contains both holes and electronic sheets because this compound contains both empty and shaded region. As we replace S by Se the heights of the peaks decreases as a results the reflectivity also decreases. It is noticed that the reflectivity is over 68% (60%) for Ba{sub 4}CuGa{sub 5}S{sub 12} (Ba{sub 4}CuGa{sub 5}Se{sub 12}) compounds within the energy range studied. This implies that the material will serve as a good reflector. By replacing S by Se the figure of merit values increases from 0.97 to 1.0, which shows the good thermoelectric behavior of both compounds. - Highlights: • DFT-FPLAPW method used for calculating the properties. • For predicting the chemical bonding the charge density behavior is studied in 2D. • The optical properties were also calculated and analyzed. • The Fermi surface is composed of two bands crossing along the EF level. • The thermoelectric properties have also been calculated.

  4. Effect of humic substances on the precipitation of calcium phosphate

    Institute of Scientific and Technical Information of China (English)

    SONG Yong-hui; Hermann H. HAHN; Erhard HOFFMANN; Peter G. WEIDLER

    2006-01-01

    For phosphorus (P) recovery from wastewater, the effect of humic substances (HS) on the precipitation of calcium phosphate was studied. Batch experiments of calcium phosphate precipitation were undertaken with synthetic water that contained 20 mg/L phosphate (as P) and 20 mg/L HS (as dissolved organic carbon, DOC) at a constant pH value in the range of 8.0-10.0. The concentration variations of phosphate, calcium (Ca) and HS were measured in the precipitation process; the crystalline state and compositions of the precipitates were analysed by powder X-ray diffraction (XRD) and chemical methods, respectively. It showed that at solution pH 8.0, the precipitation rate and removal efficiency of phosphate were greatly reduced by HS, but at solution pH ≥9.0,the effect of HS was very small. The Ca consumption for the precipitation of phosphate increased when HS was added; HS was also removed from solution with the precipitation of calcium phosphate. At solution pH 8.0 and HS concentrations ≤ 3.5 mg/L, and at pH ≥ 9.0 and HS concentrations ≤ 10 mg/L, the final precipitates were proved to be hydroxyapatite (HAP) by XRD. The increases of solution pH value and initial Ca/P ratio helped reduce the influence of HS on the precipitation of phosphate.

  5. Wire bonding in microelectronics

    CERN Document Server

    Harman, George G

    2010-01-01

    Wire Bonding in Microelectronics, Third Edition, has been thoroughly revised to help you meet the challenges of today's small-scale and fine-pitch microelectronics. This authoritative guide covers every aspect of designing, manufacturing, and evaluating wire bonds engineered with cutting-edge techniques. In addition to gaining a full grasp of bonding technology, you'll learn how to create reliable bonds at exceedingly high yields, test wire bonds, solve common bonding problems, implement molecular cleaning methods, and much more. Coverage includes: Ultrasonic bonding systems and technologies, including high-frequency systems Bonding wire metallurgy and characteristics, including copper wire Wire bond testing Gold-aluminum intermetallic compounds and other interface reactions Gold and nickel-based bond pad plating materials and problems Cleaning to improve bondability and reliability Mechanical problems in wire bonding High-yield, fine-pitch, specialized-looping, soft-substrate, and extreme-temperature wire bo...

  6. [Application of phosphates and phosphonates prodrugs in drug research and development].

    Science.gov (United States)

    Ji, Xun; Wang, Jiang; Zhang, Lei; Zhao, Lin-Xiang; Jiang, Hua-Liang; Liu, Hong

    2013-05-01

    Based on the character of the molecular structure, the prodrugs of phosphates and phosphonates were divided into two categories. The first is the drug which contained the phosphate group, introducing protected groups to increase lipophilicity and improve bioavailability. The other one is the drug which had no phosphate group, introducing the phosphate group into molecules to enhance the solubility, regulate the distribution coefficient and enhance the drug-like property. This review focuses on the application of phosphates and phosphonates in drug research and development based on improvement of physico-chemical property, drug safety and the pharmacokinetics.

  7. Practical application of phosphate treatment

    Energy Technology Data Exchange (ETDEWEB)

    Caravaggio, Mike [Integrated Chemistry Solutions Pte. Ltd., Singapore (Singapore)

    2011-05-15

    Phosphate treatment has been applied to subcritical fossil power boilers for well over half a century, as well as being used frequently in heat recovery steam generators. The use of this treatment has evolved over the decades, with the operating sodium to phosphate ratio being the defining factor for the evolution of the treatment. The evolving prescribed sodium to phosphate ratios have been based on the scientific research results and operating experience available at the time, and in the latest EPRI Guidelines issued in 2004 are set at a minimum sodium to phosphate ratio of 3:1, with provision to add up to 1 mg . L{sup -1} of additional free caustic. The ratio limitation has always been set in an effort to minimize the potential for corrosion caused by the potential misapplication of the treatment. Typically, the operating ranges for phosphate treatments are depicted on an x-y plot with the x-axis the phosphate concentration and the y-axis the corrected pH value based on the maximum sodium to phosphate ratio allowed for by the treatment. These operating range plots define the theoretical operating range of a phosphate treatment. This paper briefly discusses the origin of the current phosphate control limits in the EPRI Guidelines, discusses phosphate chemistry, outlines the limitations involved when applying a phosphate treatment and provides additional practical guidance for overcoming these limitations and minimizing the potential for corrosion induced by the incorrect application of a phosphate treatment. (orig.)

  8. Proton transport properties of tin phosphate, chromotropic acid anchored onto tin phosphate and tin phenyl phosphonate

    Indian Academy of Sciences (India)

    Chithra Sumej; P P Sharmila; Nisha J Tharayil; S Suma

    2013-02-01

    Tin (IV) phosphates of the class of tetravalent metal acid (TMA) salts have been synthesized by sol–gel method. The functionalized materials of tin (IV) phosphate (SnP) like chromotropic acid anchored tin phosphate (SnPCA) and tin phenyl phosphonate (SnPP) were also synthesized. These materials have been characterized for elemental analysis (ICP–AES), thermal analysis, X-ray analysis and FTIR spectroscopy. Chemical resistivity of these materials has been accessed in acidic, basic and organic solvent media. The proton present in the structural hydroxyl groups indicates good potential for TMA salts to exhibit solid-state proton conduction. The transport properties of these materials have been explored by measuring specific proton conductance at different temperatures. Based on the specific conduction data and Arrhenius plots, a suitable mechanism has been proposed.

  9. Correlation of Fe2+ isomer shifts with bond lengths and bond strengths in neso- and sorosilicates

    Institute of Scientific and Technical Information of China (English)

    李哲; E.DeGrave

    1995-01-01

    An evaluation of Mbssbauer isomer shift and quadrupole splitting data of Fe2+ in a number of structurally well characterized neso- and sorosilicates is presented. It is found that the nearly linear correlations exist both between the isomer shift and the bond length and between the isomer shift and the bond strength. These correlations are discussed on the basis of the variation of the s-electron density at the Fe2+ nuclei with the chemical bond characteristics.

  10. Structure and bonding of second-row hydrides

    OpenAIRE

    Blinder, S. M.

    2014-01-01

    The atomic orbitals, hybridization and chemical bonding of the most common hydrides of boron, carbon, nitrogen and oxygen are described. This can be very instructive for beginning students in chemistry and chemical physics.

  11. Determination of Chemical Bond of Tetrahedral Amorphous Carbon Films by Ellipsometry Approach%椭偏法表征四面体非晶碳薄膜的化学键结构

    Institute of Scientific and Technical Information of China (English)

    李晓伟; 周毅; 孙丽丽; 汪爱英

    2012-01-01

    Tetrahedral amorphous carbon (ta-C) films under different substrate negative bias are prepared by a home developed filtered cathodic vacuum arc (FCVA) technology with double bend shape. The film thickness is measured by a combined spectrophotometry and spectroscopic ellipsometry (SE) approach; the chemical bonds including sp2C and sp3C are gained by the fitted ellipsometry method. Furthermore,the accuracy of ellipsometry results is evaluated by comparing with those of X-ray photoelectron spectroscopy (XPS) and Raman spectra. The results indicate that the minimum thickness of ta-C film of 33. 9 nm is obtained when the bias voltage is -100 V; with the increase of bias voltage,the optical gaps and the content of sp3C atomic bond decrease,while the sp2C content increases correspondingly. By comparison with the results of XPS and Raman spectra,it is found that when the optical constants of sp2C model are represented by the glassy carbon and the fitting wavelength ranges are chosen from 250 to 1700 nm,the best fitting result of atomic bonds of ta-C films can be deduced by the ellipsometry method. Therefore,it could be said that the elliposometry method is a quite promising method to characterize the atomic bonds of ta-C films including sp2C and sp3C,as a new nondestructive,fast,quantitative and easy way.%采用自主研制的双弯曲磁过滤阴极真空电弧(FCVA)技术,在不同衬底负偏压下制备了四面体非晶碳(ta-C)薄膜.通过分光光度计和椭偏(SE)联用技术精确测量了薄膜厚度,重点采用椭偏法对不同偏压下制备的ta-C薄膜sp3C键和sp2C键结构进行了拟合表征,并与X射线光电子能谱(XPS)和拉曼光谱的实验结果相对比,分析了非晶碳结构的椭偏拟合新方法可靠性.结果表明,在-100 V偏压时薄膜厚度最小,为33.9 nm;随着偏压的增加,薄膜中的sp2C含量增加,sp3C含量减小,光学带隙下降.对比结果发现,椭偏法作为一种无损、简易、快速的表征

  12. Halogen bonds in crystal engineering: like hydrogen bonds yet different.

    Science.gov (United States)

    Mukherjee, Arijit; Tothadi, Srinu; Desiraju, Gautam R

    2014-08-19

    The halogen bond is an attractive interaction in which an electrophilic halogen atom approaches a negatively polarized species. Short halogen atom contacts in crystals have been known for around 50 years. Such contacts are found in two varieties: type I, which is symmetrical, and type II, which is bent. Both are influenced by geometric and chemical considerations. Our research group has been using halogen atom interactions as design elements in crystal engineering, for nearly 30 years. These interactions include halogen···halogen interactions (X···X) and halogen···heteroatom interactions (X···B). Many X···X and almost all X···B contacts can be classified as halogen bonds. In this Account, we illustrate examples of crystal engineering where one can build up from previous knowledge with a focus that is provided by the modern definition of the halogen bond. We also comment on the similarities and differences between halogen bonds and hydrogen bonds. These interactions are similar because the protagonist atoms-halogen and hydrogen-are both electrophilic in nature. The interactions are distinctive because the size of a halogen atom is of consequence when compared with the atomic sizes of, for example, C, N, and O, unlike that of a hydrogen atom. Conclusions may be drawn pertaining to the nature of X···X interactions from the Cambridge Structural Database (CSD). There is a clear geometric and chemical distinction between type I and type II, with only type II being halogen bonds. Cl/Br isostructurality is explained based on a geometric model. In parallel, experimental studies on 3,4-dichlorophenol and its congeners shed light on the nature of halogen···halogen interactions and reveal the chemical difference between Cl and Br. Variable temperature studies also show differences between type I and type II contacts. In terms of crystal design, halogen bonds offer a unique opportunity in the strength, atom size and interaction gradation; this may be

  13. Comprehensive analysis of individual pulp fiber bonds quantifies the mechanisms of fiber bonding in paper

    Science.gov (United States)

    Hirn, Ulrich; Schennach, Robert

    2015-05-01

    The process of papermaking requires substantial amounts of energy and wood consumption, which contributes to larger environmental costs. In order to optimize the production of papermaking to suit its many applications in material science and engineering, a quantitative understanding of bonding forces between the individual pulp fibers is of importance. Here we show the first approach to quantify the bonding energies contributed by the individual bonding mechanisms. We calculated the impact of the following mechanisms necessary for paper formation: mechanical interlocking, interdiffusion, capillary bridges, hydrogen bonding, Van der Waals forces, and Coulomb forces on the bonding energy. Experimental results quantify the area in molecular contact necessary for bonding. Atomic force microscopy experiments derive the impact of mechanical interlocking. Capillary bridges also contribute to the bond. A model based on the crystal structure of cellulose leads to values for the chemical bonds. In contrast to general believe which favors hydrogen bonding Van der Waals bonds play the most important role according to our model. Comparison with experimentally derived bond energies support the presented model. This study characterizes bond formation between pulp fibers leading to insight that could be potentially used to optimize the papermaking process, while reducing energy and wood consumption.

  14. Biomimetic calcium phosphate coating on Ti-7.5Mo alloy for dental application.

    Science.gov (United States)

    Escada, A L A; Machado, J P B; Schneider, S G; Rezende, M C R Alves; Claro, A P R Alves

    2011-11-01

    Titanium and its alloys have been used as bone-replacement implants due to their excellent corrosion resistance and biocompatibility. However, a titanium coating is a bioinert material and cannot bond chemically to bone tissue. The objective of this work was to evaluate the influence of alkaline treatment and heat treatment on the formation of calcium phosphate layer on the surface of a Ti-7.5Mo alloy after soaking in simulated body fluid (SBF). Thirty six titanium alloy plates were assigned into two groups. For group I, samples were immersed in a 5.0-M NaOH aqueous solution at 80°C for 72 h, washed with distilled water and dried at 40°C for 24 h. For group II, after the alkaline treatment, samples were heat-treated at 600°C for 1 h in an electrical furnace in air. Then, all samples were immersed in SBF for 7 or 14 days to allow the formation of a calcium phosphate coating on the surface. The surfaces were characterized using SEM, EDS, AFM and contact angle measurements.

  15. A natural orbital analysis of the long range behavior of chemical bonding and van der Waals interaction in singlet H2: the issue of zero natural orbital occupation numbers.

    Science.gov (United States)

    Sheng, X W; Mentel, Ł M; Gritsenko, O V; Baerends, E J

    2013-04-28

    This paper gives a natural orbital (NO) based analysis of the van der Waals interaction in (singlet) H2 at long distance. The van der Waals interaction, even if not leading to a distinct van der Waals well, affects the shape of the interaction potential in the van der Waals distance range of 5-9 bohrs and can be clearly distinguished from chemical bonding effects. In the NO basis the van der Waals interaction can be quantitatively covered with, apart from the ground state configurations (1σ(g))(2) and (1σ(u))(2), just the 4 configurations (2σ(g))(2) and (2σ(u))(2), and (1π(u))(2) and (1π(g))(2). The physics of the dispersion interaction requires and explains the peculiar relatively large positive CI coefficients of the doubly excited electron configurations (2σ(u))(2) and (1π(g))(2) (the occupancy amplitudes of the 2σ(u) and 1π(gx, y) NOs) in the distance range 5-9 bohrs, which have been observed before by Cioslowski and Pernal [Chem. Phys. Lett. 430, 188 (2006)]. We show that such positive occupancy amplitudes do not necessarily lead to the existence of zero occupation numbers at some H-H distances.

  16. Calcium Phosphate Biomaterials: An Update

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Current calcium phosphate (CaP) biomaterials for bone repair, substitution, augmentation and regeneration include hydroxyapatite ( HA ) from synthetic or biologic origin, beta-tricalcium phosphate ( β-TCP ) , biphasic calcium phosphate (BCP), and are available as granules, porous blocks, components of composites (CaP/polymer) cements, and as coatings on orthopedic and dental implants. Experimental calcium phosphate biomaterials include CO3- and F-substituted apatites, Mg-and Zn-substituted β-TCP, calcium phosphate glasses. This paper is a brief review of the different types of CaP biomaterials and their properties such as bioactivity, osteoconductivity, osteoinductivity.

  17. Removal of Phosphate from Synthetic Aqueous Solution by Adsorption with Dolomite from Padalarang

    Directory of Open Access Journals (Sweden)

    Fadjari Lucia Nugroho

    2014-12-01

    Full Text Available The presence of phosphate in wastewaters can cause eutrophication of surface water bodies leading to algal-blooming in the aquatic environment and degradation of water quality. Phosphate removal from wastewaters by conventional biological treatment removes only 10-30% of the phosphate, whilst chemical treatment using precipitants such as calcium or iron salts, although effective, is expensive and produces water-rich sludge which must be further treated. Hence, phosphate removal by adsorption in the form of Ca -phosphate has been proposed as an alternative to the more traditional methods. This study investigated the feasibility of using dolomite–a common sedimentary rock–from Padalarang, West Java, Indonesia as the adsorbent for the removal of phosphate from synthetic aqueous solution. Chemical analysis revealed that the Padalarang dolomite contains 33.6-36.2% CaO. Batch experiments at room temperature indicated that optimum removal of phosphate was achieved at pH 9. At 25°C , where increasing concentrations of phosphate (10–100 mg/L increased phosphate adsorption (2.15-31.3 mg/g by the dolomite. The adsorption of phosphate could be described by the Langmuir isotherm model, with constants Qm= 476.19 mg/g, K L= 0,00106 L/mg and equilibrium parameter (R L: 0.904 – 0.989. Phosphate adsorption by dolomite not only permits its removal but also its potential recovery for reuse.

  18. Constructing Models in Teaching of Chemical Bonds: Ionic Bond, Covalent Bond, Double and Triple Bonds, Hydrogen Bond and Molecular Geometry

    Science.gov (United States)

    Uce, Musa

    2015-01-01

    Studies in chemistry education show that chemistry topics are considered as abstract, complicated and hard to understand by students. For this reason, it is important to develop new materials and use them in classes for better understanding of abstract concepts. Moving from this point, a student-centered research guided by a teacher was conducted…

  19. Biomediated continuous release phosphate fertilizer

    Science.gov (United States)

    Goldstein, Alan H.; Rogers, Robert D.

    1999-01-01

    A composition is disclosed for providing phosphate fertilizer to the root zone of plants. The composition comprises a microorganism capable of producing and secreting a solubilization agent, a carbon source for providing raw material for the microorganism to convert into the solubilization agent, and rock phosphate ore for providing a source of insoluble phosphate that is solubilized by the solubilization agent and released as soluble phosphate. The composition is provided in a physical form, such as a granule, that retains the microorganism, carbon source, and rock phosphate ore, but permits water and soluble phosphate to diffuse into the soil. A method of using the composition for providing phosphate fertilizer to plants is also disclosed.

  20. Phosphate adsorption on lanthanum loaded biochar.

    Science.gov (United States)

    Wang, Zhanghong; Shen, Dekui; Shen, Fei; Li, Tianyu

    2016-05-01

    To attain a low-cost and high-efficient phosphate adsorbent, lanthanum (La) loaded biochar (La-BC) prepared by a chemical precipitation method was developed. La-BC and its pristine biochar (CK-BC) were comparatively characterized using zeta potential, BET surface area, scanning electron microscopy/energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The adsorption ability and the mechanisms during adsorption process for the La-BC samples were also investigated. La loaded on the surface of biochar can be termed as La-composites (such as LaOOH, LaONO3 and La(OH)3), leading to the decrease of negative charge and surface area of biochar. La-BC exhibited the high adsorption capacity to phosphate compared to CK-BC. Adsorption isotherm and adsorption kinetic studies showed that the Langmuir isotherm and second order model could well describe the adsorption process of La-BC, indicating that the adsorption was dominated by a homogeneous and chemical process. The calculated maximum adsorption capacity was as high as 46.37 mg g(-1) (computed in P). Thermodynamic analysis revealed that the adsorption was spontaneous and endothermic. SEM, XRD, XPS and FT-IR analysis suggested that the multi-adsorption mechanisms including precipitation, ligand exchange and complexation interactions can be evidenced during the phosphate adsorption process by La-composites in La-BC.