Academic literature on the topic 'Oxygen and sodium nuclei structure'
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Journal articles on the topic "Oxygen and sodium nuclei structure"
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Bosáček, Vladimír, Stanislav Vratislav, and Mája Dlouhá. "Bridging Methoxy Groups in NaY, NaX and NaLSX Zeolites." Collection of Czechoslovak Chemical Communications 69, no. 8 (2004): 1537–52. http://dx.doi.org/10.1135/cccc20041537.
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Distribution of chemisorbed methyl groups and sodium cations in the structure of NaY, NaX and NaLSX zeolites was estimated by neutron diffraction. Chemisorbed methyl groups were prepared in the structure by reaction of methyl iodide with reactive sodium cations available in SII and SIII positions of faujasites. Methyl cations CH3+, formed in the reaction, react immediately with the lattice oxygen forming surface bonded methyl groups in bridging configuration. 13C NMR signals of chemisorbed surface species and their linear dependence on the intermediate electronegativity of the zeolite lie in the interval from 53 ppm for most basic CsLSX to 58 ppm TMS for stabilized and acid leached sample of H,NaY-St. Changes in the distribution of structural sodium cations in the lattice after chemisorption of methyl cations have been detected. C-O distances in surface methoxy groups in void cavities were longer than in ordinary crystalline organometallic compounds with bridging methoxy groups. The location of chemisorbed methyl groups at the O1 lattice oxygen type was most probable for NaY. Nuclear densities of chemisorbed methyl groups were detected in NaX at O1 and at O4 lattice oxygens. The origin of the split signal at 58 ppm on NaX and NaLSX samples has been discussed.
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Starratt, Alvin N., Edmund W. B. Ward, and J. B. Stothers. "Coprinolone and Δ6-coprinolone: new sesquiterpenes from Coprinus psychromorbidus." Canadian Journal of Chemistry 67, no. 3 (March 1, 1989): 417–27. http://dx.doi.org/10.1139/v89-065.
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The structure of coprinolone (1), an oxygen-bridged protoilludane from the W2 isolate of the fungus Coprinuspsychromorbidus, has been elucidated by chemical transformations and detailed 1H and 13C magnetic resonance studies, including homo- and heteronuclear correlation spectra. The 1H–1H coupling data and nuclear Overhauser difference spectra for 1 and derived isomers led to the establishment of its stereochemistry. A second metabolite was identified as Δ6-coprinolone (20) by spectroscopic results. Confirmatory evidence in support of the structures was obtained from the labelling patterns of the compounds from cultures supplemented with sodium [1,2-13C2]acetate. Keywords: coprinolone, Δ6-coprinolone, protoilludane, sesquiterpenes, NMR.
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Wolfe, Saul, Raymond John Bowers, Hee-Sook Shin, Chang-Kook Sohn, Donald Fredric Weaver, and Kiyull Yang. "Phenceptin: a biomimetic model of the phenytoin receptor." Canadian Journal of Chemistry 66, no. 11 (November 1, 1988): 2751–62. http://dx.doi.org/10.1139/v88-425.
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5,5-Diphenylhydanytoin (phenytoin) is the most widely used anticonvulsant drug, but has many side effects. Although its chemical mode of action is unknown, phenytoin is believed to function primarily by interference with the transport of sodium ions across the neuronal membrane. Structure–activity and lipophilicity–activity studies suggest that the drug interacts with its receptor through hydrogen bonding to the N3—C4 amide bond, and an aromatic–aromatic interaction with the C5 substituent. Since sodium channels are cysteine-rich peptides, whose function depends upon the cysteine[Formula: see text]cystine redox process, it has been hypothesized that the action of the phenytoin receptor may be mimicked by a properly designed cyclodepsipeptide containing a cystinyl moiety, a cavity lined with five oxygen atoms oriented in the trigonal-bipyramidal manner appropriate for selective transport of sodium ions, and a site for the binding of phenytoin. A computer programme and strategy were developed to permit the three-dimensional structures of potential target molecules to be viewed, prior to synthesis. Use of this programme led to the discovery of Boc-L-cystinyl-glycyl-L-prolyl-glycyl-L-prolyl-L-cystine-OCHPh2. This compound, termed phenceptin, was synthesized from a linear precursor containing tert-butoxycarbonyl protection at the N-terminus, benzhydryl ester protection at the C-terminus, and trityl protection at sulfur. Detritylation and cyclization to phenceptin were accomplished with iodine in methanol–pyridine. Using an n-octanol membrane to study the kinetics of ion transport, phenceptin was found to transport sodium ions selectively, but only in its oxidized, cyclic form. This transport was inhibited significantly by one mol-equiv. of phenytoin, and not at all by biologically inactive analogs of the drug. The nature of the binding of phenytoin to phenceptin was examined by nuclear magnetic resonance, in n-C8D17-OH solvent, and found to involve hydrogen bonding of the drug to a glycine residue whose oxygen atom is involved in complexation to sodium ions.
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Dickson, R. S., and J. A. Weil. "The magnetic properties of the oxygen-hole aluminum centres in crystalline SiO2. IV. [AlO4/Na]+." Canadian Journal of Physics 68, no. 7-8 (July 1, 1990): 630–42. http://dx.doi.org/10.1139/p90-094.
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The centre [AlO4/Na]+, formed in α-quartz by X irradiation at 77 K, contains an aluminum ion substituted for a silicon ion, with an electron hole on a nearest-neighbor oxygen ion, and an interstitial sodium ion, which acted as a charge compensator before loss of the electron. Electron paramagnetic resonance spectra of this centre at 35 K have yielded spin-Hamiltonian nuclear quadrupole and hyperfine parameter matrices [Formula: see text], Ā(23Na), and [Formula: see text], in addition to matrices [Formula: see text] and Ā(27Al) more accurate than those measured previously. The line width anisotropy is parameterized by an appropriate matrix W. Hartree–Fock molecular orbital geometry optimizations on a small model cluster, [Al(OH)4Na]+, and hyperfine matrices calculated for the lowest energy configuration, confirm that [AlO4/Na]+ has the same type of structure as [AlO4/H]+ and [AlO4/Li]+; the hole is on an oxygen ion linked to the aluminum ion by a "short" bond, and the sodium ion is in the nearby c-axis channel on the long-bond side of the aluminum ion. The thermal decay of [AlO4/Na]+ to [AlO4]0, measurable at 154 K and above, and the subsequent formation of centres [GeO4/Na]0 from [GeO4]− were studied.
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Yan, Lu, and Fan Ping. "Synthesis and Study of 4, 4-12-12 Alkyl Phenol Polyoxyethylene Sulfonate Gemini Surfactant." Recent Innovations in Chemical Engineering (Formerly Recent Patents on Chemical Engineering) 12, no. 4 (October 28, 2019): 262–74. http://dx.doi.org/10.2174/2405520412666190723112325.
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Background: Gemini surfactants have good prospect of application development in various fields for their superior performance in foaming, wettability, and emulsification with lower critical micelle concentration (CMC) than conventional mono-surfactants. Objective: The purpose of this study was to synthesize an ionic sulfonate Gemini surfactant, which is mainly used as an oil flooding agent, to improve oil recovery and reduce oil production cost. Methods: With 4-dodecyl phenol, diethylene glycol and triethylene glycol as the raw materials to synthesize two sulfonate Gemini surfactants. The single factor experiment combined with Box-Behnken center composite experimental design, the optimum reaction conditions were determined. The optimal reaction condition of sulfonation was determined by orthogonal test. The product structure was characterized by nuclear magnetic resonance and infrared. Results: The mass fraction of sodium hydroxide ω(NaOH), temperature and the quality ratio of hexadecyl trimethyl ammonium bromide to dodecyl phenol were 18%, 93.5°C and 14.2%, respectively. Under the condition of ice bath, the molar ratio of chlorosulfonic acid to 4, 4- 12-12 alkyl phenol polyoxyethylene ether was 2.02:1 and reaction for 5h. The critical micelle concentration was determined to be 2×10-4, 1.05×10-4, respectively. Conclusion: Two sulfonate Gemini surfactants, namely 5, 5-dilauryl alkyl-2,2'-(diethylene glycol oxygen base) sodium diphenyl sulfonate and 5,5-dilauryl alkyl-2,2'-(triethylene glycol oxygen base) sodium diphenyl sulfonate (recorded as III and IV, respectively) were synthesized. The synthesized surfactants have excellent emulsification ability.
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Stefanovsky, Sergey V., Andrey A. Shiryaev, Michael B. Remizov, Elena A. Belanova, Pavel A. Kozlov, and Boris F. Myasoedov. "Valence and Local Environment of Molybdenum in Aluminophosphate Glasses for Immobilization of High Level Waste from Uranium-Graphite Reactor Spent Nuclear Fuel Reprocessing." MRS Proceedings 1744 (2015): 73–78. http://dx.doi.org/10.1557/opl.2015.299.
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ABSTRACTTwo Mo-bearing glasses considered as candidate forms for high level waste (HLW) a uranium-graphite reactor spent nuclear fuel (SNF) reprocessing were characterized. Incorporation of Mo in sodium aluminophosphate (SAP) glass increases its tendency to devitrification with segregation of orthophosphate phases. Valence state and local environment of Mo in the materials containing ∼2 wt.% MoO3 were determined by X-ray absorption fine structure (XAFS) spectroscopy. In the quenched samples composed of major vitreous and minor AlPO4 nearly all Mo is located in the vitreous phase as [Mo6+О6] units whereas in the annealed samples Mo is partitioned among vitreous and one or two orthophosphate crystalline phases in favor of the vitreous phase. Mo predominantly exists in a hexavalent state in distorted octahedral environment. Four oxygen ions are positioned at a distance of ∼1.71-1.73 Å and two - at a distance of 2.02-2.04 Å. Minor Mo(V) is also present as indicated by a response in EPR spectra with g ≈ 1.911-1.915.
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Berry, David Eric, Kathryn Anne Beveridge, Jane Browning, Gordon William Bushnell, and Keith Roger Dixon. "Ligand properties of phosphinito platinum complexes: 31P and 195Pt nuclear magnetic resonance studies and the crystal and molecular structure of [Cl(Et3P)Pt(μ-PPh2O)2Pt(PEt3)2][BF4]." Canadian Journal of Chemistry 64, no. 9 (September 1, 1986): 1903–11. http://dx.doi.org/10.1139/v86-314.
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Reaction of sodium hydride in tetrahydrofuran with the hydrogen-bonded phosphinito complex, [PtCl(PEt3){(PPh2O)2H}], gives a solution of the salt, [PtCl(PEt3){(PPh2O)2Na}], which is a precusor to synthesis of other bimetallic derivatives, [PtCl(PEt3){(μ-PPh2O)2Q}]n+: n = 0, Q = Rh(COD) or Ir(COD); n = 1, Q = Pd(PEt3)2 or Pt(PEt3)2. Detailed 31P and 195Pt nmr studies are reported for these and related examples including a titanium complex (n = 0, Q = Ti(acac)Cl2) synthesised by direct reaction of [PtCl(PEt3){(PPh2O)2H}] with [TiCl2(acac)2]. The diplatinurn complex, [Cl(PEt3)Pt(μ-PPh2O)2Pt(PEt3)2][BF4] crystallizes in the monoclinic space group P21/n, with a = 13.018(2), b = 34.205(9), c = 11.279(2) Å, β = 91.71(2)°. A complete X-ray diffraction study shows that the two platinum centres are significantly non-planar and are linked by the phosphinito ligands to form a six-membered ring in a boat conformation with phosphorus and oxygen atoms forming the prows of the boat.
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Caurant, Daniel, Arnaud Quintas, Odile Majérus, Thibault Charpentier, and I. Bardez. "Structural Role and Distribution of Alkali and Alkaline-Earth Cations in Rare Earth-Rich Aluminoborosilicate Glasses." Advanced Materials Research 39-40 (April 2008): 19–24. http://dx.doi.org/10.4028/www.scientific.net/amr.39-40.19.
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The structure of a seven oxide aluminoborosilicate simplified nuclear glass, bearing a high amount of neodymium or lanthanum oxide (16 wt%), alkali and alkaline earth cations is studied. Nd3+ or La3+ are supposed to simulate the trivalent lanthanides and minor actinides present in nuclear wastes. In the studied glass composition, lanthanide ions have a modifying role and are located in highly depolymerized regions of the structure as shown by neodymium optical absorption and EXAFS spectroscopies. Both alkali and alkaline earth cations are present around Nd3+ ions enabling their stabilization in glass structure near non-bridging oxygen atoms (NBOs). We show that both the nature of alkali R+ and alkaline earth R'2+ cations and the K = [R'O]/([R2O]+[R'O]) ratio can greatly influence the structure of the aluminoborosilicate glass network. Three glass series were prepared for which: (i) K ratio was varied from 0 to 0.5 (Na+ and Ca2+ being respectively the only alkali and alkaline-earth cations), (ii) the nature of R+ cation was varied from Li+ to Cs+ (Ca2+ being the only alkaline earth cation and K = 0.3), (iii) the nature of R'2+ cation was varied from Mg2+ to Ba2+ (Na+ being the only alkali cation and K = 0.3). 27Al MAS NMR spectroscopy results show that (AlO4)- units are preferentially charge compensated by alkali cations rather than by alkaline-earth cations. Both R+ and R’2+ cations can compensate (BO4)- units. Nevertheless, whereas the proportion N4 of (BO4)- units increases with the size of R'2+ cations, the evolution of N4 with R+ cation size for glasses of the R series is not monotonous. The evolution of sodium ions distribution trough glass structure is followed by 23Na MAS NMR spectroscopy.
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Lee, Sung Keun, George D. Cody, Yingwei Fei, and Bjorn O. Mysen. "Oxygen-17 Nuclear Magnetic Resonance Study of the Structure of Mixed Cation Calcium−Sodium Silicate Glasses at High Pressure: Implications for Molecular Link to Element Partitioning between Silicate Liquids and Crystals." Journal of Physical Chemistry B 112, no. 37 (September 18, 2008): 11756–61. http://dx.doi.org/10.1021/jp804458e.
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Kappaun, Karine, Anne H. S. Martinelli, Valquiria Broll, Barbara Zambelli, Fernanda C. Lopes, Rodrigo Ligabue-Braun, Leonardo L. Fruttero, et al. "Soyuretox, an Intrinsically Disordered Polypeptide Derived from Soybean (Glycine Max) Ubiquitous Urease with Potential Use as a Biopesticide." International Journal of Molecular Sciences 20, no. 21 (October 30, 2019): 5401. http://dx.doi.org/10.3390/ijms20215401.
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Ureases from different biological sources display non-ureolytic properties that contribute to plant defense, in addition to their classical enzymatic urea hydrolysis. Antifungal and entomotoxic effects were demonstrated for Jaburetox, an intrinsically disordered polypeptide derived from jack bean (Canavalia ensiformis) urease. Here we describe the properties of Soyuretox, a polypeptide derived from soybean (Glycine max) ubiquitous urease. Soyuretox was fungitoxic to Candida albicans, leading to the production of reactive oxygen species. Soyuretox further induced aggregation of Rhodnius prolixus hemocytes, indicating an interference on the insect immune response. No relevant toxicity of Soyuretox to zebrafish larvae was observed. These data suggest the presence of antifungal and entomotoxic portions of the amino acid sequences encompassing both Soyuretox and Jaburetox, despite their small sequence identity. Nuclear Magnetic Resonance (NMR) and circular dichroism (CD) spectroscopic data revealed that Soyuretox, in analogy with Jaburetox, possesses an intrinsic and largely disordered nature. Some folding is observed upon interaction of Soyuretox with sodium dodecyl sulfate (SDS) micelles, taken here as models for membranes. This observation suggests the possibility for this protein to modify its secondary structure upon interaction with the cells of the affected organisms, leading to alterations of membrane integrity. Altogether, Soyuretox can be considered a promising biopesticide for use in plant protection.
Dissertations / Theses on the topic "Oxygen and sodium nuclei structure"
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Lewis, D. G. "A study of the reaction (sup(6)Li,d) on light nuclei." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355737.
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Ashbrook, Sharon Elizabeth. "New NMR techniques for the study of quadrupolar nuclei." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342238.
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Hawcroft, Deborah. "A search for superdeformed and hyperdeformed states in '2'2'2Th and '2'3'2U." Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367227.
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Rander, Torbjörn. "Photoelectron Spectroscopy on Atoms, Molecules and Clusters : The Geometric and Electronic Structure Studied by Synchrotron Radiation and Lasers." Doctoral thesis, Uppsala University, Department of Physics, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8343.
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Atoms, molecules and clusters all constitute building blocks of macroscopic matter. Therefore, understanding the electronic and geometrical properties of such systems is the key to understanding the properties of solid state objects.
In this thesis, some atomic, molecular and cluster systems (clusters of O2, CH3Br, Ar/O2, Ar/Xe and Ar/Kr; dimers of Na; Na and K atoms) have been investigated using synchrotron radiation, and in the two last instances, laser light. We have performed x-ray photoelectron spectroscopy (XPS) on all of these systems. We have also applied ultraviolet photoelectron spectroscopy (UPS), resonant Auger spectroscopy (RAS) and near-edge x-ray absorption spectroscopy (NEXAFS) to study many of the systems. Calculations using ab initio methods, namely density functional theory (DFT) and Møller-Plesset perturbation theory (MP), were employed for electronic structure calculations. The geometrical structure was studied using a combination of ab initio and molecular dynamics (MD) methods.
Results on the dissociation behavior of CH3Br and O2 molecules in clusters are presented. The dissociation of the Na2 molecule has been characterized and the molecular field splitting of the Na 2p level in the dimer has been measured. The molecular field splitting of the CH3Br 3d level has been measured and the structure of CH3Br clusters has been determined to be similar to the structure of the bulk solid. The diffusion behavior of O2, Kr and Xe on large Ar clusters, as a function of doping rate, has been investigated. The shake-down process has been observed from excited states of Na and K. Laser excited Na atoms have been shown to be magnetically aligned. The shake-down process was used to characterize the origin of various final states that can be observed in the spectrum of ground-state K.
Book chapters on the topic "Oxygen and sodium nuclei structure"
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"Structure and Properties of Composite Adsorbents Salt Inside Porous Matrix." In Technology Development for Adsorptive Heat Energy Converters, 43–87. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-4432-7.ch003.
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The chapter is devoted to structure and properties of composite adsorbents ‘salt inside porous matrix'. Characteristics of adsorbents ‘salt inside porous matrix', such as ‘zeolite – crystalline hydrate', ‘vermiculite – crystalline hydrate', ‘silica gel – crystalline hydrate' were analysed. Main advantages of composite adsorbents are shown to be higher adsorptive capacity and lower regeneration temperature as compared with host matrix. Adsorptive capacities of composite materials are shown to be significantly enhanced by introduction of salts in host matrix such as zeolite, vermiculite, or silica gel. Water uptake by composite adsorbent is shown to be increased by rising the salt content in it. The drawback of most of existing impregnation technologies is shown to be impossibility of obtaining composite with salt content more than 40 – 60% along with complexity. Sol gel method is shown to be an alternative for conventional impregnation methods. Properties of adsorbents ‘silica gel – sodium sulphate' synthesized according to sol gel method developed by authors were considered. The composite ‘silica gel – sodium sulphate' composition and structure were studied by IR-spectroscopy and wide-angle x-ray scattering. Adsorptive properties of crystalline Na2SO4 when allocated in silicon oxygen matrix are shown to result from dispersion up to nanoscale. Adsorptive capacities and heat of adsorption of composites ‘silica gel – sodium sulphate' and ‘silica gel – sodium acetate' surpass almost by 30% the value calculated from the linear superposition of the sorption capacities of the sorbent and massive salt. Their adsorption properties are shown to be not a linear combination of properties of silica gel and salt. The formation of a unique structure promoting an increase in the rate of reaction between crystalline hydrates and water vapor in the developed pores of the silicon-oxygen matrix is confirmed. It leads to increasing the heat of adsorption and the heat energy storage density. Strong difference of water sorption kinetic curves of composite ‘silica gel – sodium sulphate' and massive sodium sulphate is revealed. The correlation of their composition, structure, water adsorption kinetic, and operating characteristic as heat storage material is stated.
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Glusker, Jenny Pickworth, and Kenneth N. Trueblood. "Introduction." In Crystal Structure Analysis. Oxford University Press, 2010. http://dx.doi.org/10.1093/oso/9780199576340.003.0009.
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Much of our present knowledge of the architecture of molecules has been obtained from studies of the diffraction of X rays or neutrons by crystals. X rays are scattered by the electrons of atoms and ions, and the interference between the X rays scattered by the different atoms or ions. in a crystal can result in a diffraction pattern. Similarly, neutrons are scattered by the nuclei of atoms. Measurements on a crystal diffraction pattern can lead to information on the arrangement of atoms or ions within the crystal. This is the experimental technique to be described in this book. X-ray diffraction was first used to establish the three-dimensional arrangement of atoms in a crystal by William Lawrence Bragg in 1913 (Bragg, 1913), shortly after Wilhelm Conrad Röntgen had discovered X rays and Max von Laue had shown in 1912 that these X rays could be diffracted by crystals (Röntgen, 1895; Friedrich et al., 1912). Later, in 1927 and 1936 respectively, it was also shown that electrons and neutrons could be diffracted by crystals (Davisson and Germer, 1927; von Halban and Preiswerk, 1936; Mitchell and Powers, 1936). Bragg found from X-ray diffraction studies that, in crystals of sodium chloride, each sodium is surrounded by six equidistant chlorines and each chlorine by six equidistant sodiums. No discrete molecules of NaCl were found and therefore Bragg surmised that the crystal consisted of sodium ions and chloride ions rather than individual (noncharged) atoms (Bragg, 1913); this had been predicted earlier by William Barlow and William Jackson Pope (Barlow and Pope, 1907), but had not, prior to the research of the Braggs, been demonstrated experimentally. A decade and a half later, in 1928, Kathleen Lonsdale used X-ray diffraction methods to show that the benzene ring is a flat regular hexagon in which all carbon–carbon bonds are equal in length, rather than a ring structure that contains alternating single and double bonds (Lonsdale, 1928).Her experimental result, later confirmed by spectroscopic studies (Stoicheff, 1954), was of great significance in chemistry.
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Leenheer, Jerry A. "Characterization of Natural Organic Matter by Nuclear Magnetic Resonance Spectroscopy." In Nuclear Magnetic Resonance Spectroscopy in Environment Chemistry. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195097511.003.0019.
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Natural organic matter (NOM) is a major intermediate in the global carbon, nitrogen, sulfur, and phosphorus cycles. NOM is also the environmental matrix that frequently controls binding, transport, degradation, and toxicity of many organic and inorganic contaminants. Despite its importance, NOM is poorly understood at the structural chemistry level because of its molecular complexity and heterogeniety. Nuclear magnetic resonance (NMR) spectroscopy is one of the most useful spectrometric methods used to investigate NOM structure because qualitative and quantitative organic structure information for certain organic elements can be generated by NMR for NOM in both the solution and solid states under nondegradative conditions. However, NMR spectroscopy is not as sensitive as infrared or ultraviolet-visible spectroscopy; it is not at present applicable to organic oxygen and sulfur, and quantification of NMR spectra is difficult under certain conditions. The purpose of this overview is to present briefly the “state of the art” of NMR characterization of NOM, and to suggest future directions for NMR research into NOM. More comprehensive texts concerning the practice of NMR spectroscopy and its application to NOM in various environments have been produced by Wilson and by Wershaw and Mikita. Carbon, hydrogen, and oxygen are the major elements of NOM; together they comprise about 90% of the mass. The minor elements that constitute the remainder are nitrogen, sulfur, phosphorus, and trace amounts of the various halogen elements. With the exception of coal, in which carbon is the most abundant element, the order of relative abundance in NOM on an atomic basis is H > C > O > N > S > P = halogens. The optimum NMR-active nuclei for these elements are 1H, 13C, 17O, 15N, 33S, 31P, and 19F. The natural abundances and receptivities of these nuclei relative to 1H are given in Table 12.1. Quadrupolar effects for 17O, 33S, and halogen elements other than 19F lead to line broadening that greatly limits resolution in NMR studies of these elements in NOM.
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Hoyt, Douglas V., and Kenneth H. Shatten. "Observations of the Sun." In The Role of the Sun in Climate Change. Oxford University Press, 1997. http://dx.doi.org/10.1093/oso/9780195094138.003.0005.
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Our sun is a typical “second generation,” or G2, star nearly 4.5 billion years old. The sun is composed of 92.1% hydrogen and 7.8% helium gas, as well as 0.1% of such all-important heavy elements as oxygen, carbon, nitrogen, silicon, magnesium, neon, iron, sulfur, and so forth in decreasing amounts (see Appendix 3). The heavy elements are generated from nucleosynthetic processes in stars, novae, and supernovae after the original formation of the Universe. This has led to the popular statement that we are, literally, the “children of the stars” because our bodies are composed of the elements formed inside stars. From astronomical studies of stellar structure, we know that, since its beginnings, the sun’s luminosity has gradually increased by about 30%. This startling conclusion has raised the so-called faint young sun climate problem: if the sun were even a few percent fainter in the past, then Earth could have been covered by ice. In this frozen state, it might not have warmed because the ice would reflect most of the incoming solar radiation back into space. Although volcanic aerosols covering the ice, early oceans moderating the climate, and other theories have been suggested to circumvent the “faint young sun” problem, how Earth escaped the ice catastrophe remains uncertain. How can the sun generate vast amounts of energy for billions of years and still keep shining? Before nuclear physics, scientists believed the sun generated energy by means of slow gravitational collapse. Still, this process would only let the sun shine about 30 million years before its energy was depleted. To shine longer, the sun requires another energy source. We now believe that a chain of nuclear reactions occurs inside the sun, with four hydrogen nuclei fusing into one helium nucleus at the sun’s center. Because the four hydrogen nuclei have more mass than the one helium nucleus, the resulting mass deficit is converted into energy according to Einstein’s famous formula E = mc2. The energy, produced near the sun’s center, creates a central temperature of about 15 million degrees Kelvin (°K).
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Dalton, David R. "Adding Sulfur Dioxide (SO2)." In The Chemistry of Wine. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190687199.003.0028.
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The judicious use of sulfur dioxide (SO2) will inhibit the growth of microorganisms (e.g., bacteria) present on the grape skins as the berries come from the vineyard. Its early use presumes the vintner has decided that the adventitious wild yeasts which might be destroyed or inhibited by sulfur dioxide will not contribute to the vintage. It appears that Saccharomyces cerevisiae might be less susceptible to the action of sulfur dioxide than other yeasts that may be present. So, if the particular strain of S. cerevisiae used can cope, it may be able to function unimpeded. Regardless, sulfur dioxide might still be used because, in addition to suppression of deleterious microorganisms, it appears to reduce oxidation of particularly fragile white wine components. In industrial settings, both gaseous sulfur dioxide and sulfur dioxide as a liquefied gas (boiling point – 10 °C [14 °F]) are used. In either form it is a dangerous tool. It is dangerous first because it is toxic and second because an excess of it will ruin the wine. In many cases, because its value is recognized as beneficial, sulfur dioxide is replaced by addition of either sodium metabisulfite (Na2S2O5) or potassium metabisulfite (K2S2O5) with the latter generally preferred. Indeed, while it is best to look at the MSDS. (Manufacturer’s Safety Data Sheet) before use, the solubility of the two salts is the same and given as 450 grams/ liter (g/ L) at 68 °F (20 °C) and the pH on dissolution as between 3.5 and 4.5. The potassium (K) salt appears, at this writing, to be more readily available in food quality (as opposed to chemical quality) grade. So, with regard to sulfur dioxide (SO2), and as shown in Figure 17.1, its structure is much more similar to water and to ozone than it is to carbon dioxide (CO2); sulfur lies beneath oxygen (O2) in the periodic table (silicon, Si, lies beneath carbon). Nonetheless, sulfur dioxide (SO2) reacts with water much the same way that carbon dioxide (CO2) does.
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Richards, Nigel G. J. "An Introduction to the Theoretical Basis of Semi-Empirical Quantum-Mechanical Methods for Biological Chemists." In Molecular Orbital Calculations for Biological Systems. Oxford University Press, 1998. http://dx.doi.org/10.1093/oso/9780195098730.003.0007.
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Computational methods that can be employed to investigate fundamental questions concerning the complex chemical and structural behavior of biological molecules such as proteins, carbohydrates, and nucleic acids have been traditionally limited by the large number of atoms that comprise even the simplest system of biochemical interest. As a consequence, highly parameterized, empirical force field methods have been developed that describe the energy of macromolecular structures as a function of the spatial locations of the atomic nuclei. In combination with algorithms for simulating molecular dynamics, these classical models allow relatively accurate calculations of the structural and thermodynamic properties associated with proteins and nucleic acids. On the other hand, empirical approaches cannot be used to model molecular behavior that is directly dependent on electrons and their energies. For example, no information can be obtained concerning the electronic spectra of macromolecule/ligand complexes, electron transfer reactions such as those that occur within the photosynthetic reaction center, nitrogenase, an enzyme involved in nitrogen fixation, or cytochrome c oxidase which catalyzes the reduction of oxygen in the last step of aerobic respiration. Accurate modeling of transition states, excited states, and intermediates in biological catalysis requires application of quantummechanical (QM) representations since all of these phenomena depend on the distribution and/or excitation of electrons. At present, the most accurate ab initio algorithms for calculating electronic structure cannot be applied to systems comprised of hundreds of atoms, as such calculations scale as N4–N7 on most workstations, where N is the number of functions used in constructing the many-electron, molecular wavefunction. Even with the implementation of ab initio codes optimized for use on parallel computing engines, and density functional approaches, it is likely that high-accuracy QM calculations in the near future will remain limited to systems that comprise tens, rather than hundreds, of nonhydrogen atoms. Semi-empirical quantum-mechanical methods combine fundamental theoretical treatments of electronic behavior with parameters obtained from experiment to obtain approximate wavefunctions for molecules composed of hundreds of atoms.
Conference papers on the topic "Oxygen and sodium nuclei structure"
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Otake, Shiro, Masahiro Nishimura, and Ken-ichiro Sugiyama. "Oxidization and Combustion in Liquid Sodium Droplet." In 17th International Conference on Nuclear Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/icone17-75250.
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Liquid sodium is used as the coolant of the fast reactor because of its high thermal conductivity. It is superior as thermal medium in spite of high chemical reactivity with oxygen. In many cases, the combustion starts after forming the dendrite oxides on its reaction surface in oxygen atmosphere. This fact indicates that sodium doesn’t ignite and burn easily unless dendrite oxides are formed. The understanding of the formation mechanism of the dendrite oxides helps us to obtain the optimum handling of leftover non-burning sodium after the accident. However, experimental knowledge to understand the mechanism of combustion is still insufficient. The purpose of this study is to clarify the oxidization behavior of a liquid sodium droplet precisely [1]. The reason why we choose the droplet form is derived from the fact that the reaction surface can be easily observed. The experiment was carried out in a glove box filled with argon gas. A single sodium droplet was made at the tip of the nozzle and preheated at the experimental temperature. The oxidization started by supplying the gas mixture of nitrogen and oxygen. The oxygen concentration of the gas mixture and the initial sodium temperature were adopted as experimental parameters, 4% ∼ 20% O2 and 200°C ∼ 500°C respectively. When the gas mixture was supplied, the droplet surface was covered with a white oxide layer. Gradually, the dendrite oxides appeared on the lower side of the sodium droplet, and the aerosol was generated in the vapor phase area. Then, the dendrite oxides on the surface sank in the droplet and the surface became smooth again. Finally the sodium droplet was encompassed by orange flame. The dendrite oxides were found to grow bigger at the first reaction period. It is suggested that the dendrite oxides have a porous structure and the liquid sodium in the droplet is drawn up to their tips by capillary force. Then the sodium oxidization occurs at the tips. The sodium droplet covered by dendrite oxides was also found to be heated up and the dendrite oxides sank into the droplet due to the high oxygen solubility and be finally burned due to the attainment of its ignition temperature as the second reaction period. The heat generation of oxidization as the first reaction period contributed to the combustion phenomena.
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Ohno, Shuji, Takashi Takata, and Yuji Tajima. "Evaluation of Sodium Pool Fire and Thermal Consequence in Two-Cell Configuration." In 2016 24th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/icone24-61095.
Full textAbstract:
Evaluation of accidental sodium leak, combustion, and its thermal consequence is one of the important issues to be assessed in the field of sodium-cooled fast reactor (SFR) since the liquid sodium is chemically active and might give thermal load to plant building structure due to its exothermic reaction with oxygen in air atmosphere. Therefore, many experimental investigations and numerical simulation tools development have been and still now are being carried out to understand the details of sodium fire behaviors and to contribute to the investigation and preparation of appropriate mitigation measures in the plant design. From various kinds of sodium fire situations, the present paper treats the sodium pool fire and subsequent heat transfer behavior in air atmosphere two-cell geometry both experimentally and analytically because such two-cell configuration is considered as the typical one to possess important characteristic of multi-compartment system seen in an actual plant. Main description of this paper consists of a sodium pool fire experiment that was performed in a rectangular-shaped two-cell system with an opening between the cells, and the discussion of the experimental results. Inner volume of the experimental cells is about 70 m3. The amount of used sodium and the prepared pool surface area in the experiment are about 55 kg and 2.25 m2, respectively. The experiment has provided the temperature data measured in more than 100 positions for atmospheric gas and structures other than the data of oxygen concentration and suspended sodium aerosols concentration in the cells. The analyses of the measured data clarify the basic characteristics of sodium pool combustion and consequential heat and mass transfer in the cells, for instance, suggesting several features of multidimensional thermal-hydraulic behaviors such as thermal stratification near the opening between the two cells. In the discussion, numerical analysis using a lumped-parameter based zonal model safety analysis code ‘SPHINCS’ and the comparison of its results with the experimental data are also carried out to investigate the validity and applicability of the code to this type of sodium fire situation.
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Balbaud-Ce´le´rier, F., and L. Martinelli. "Modelling of Fe-Cr Martensitic Steels Corrosion in Liquid Lead Alloys." In 17th International Conference on Nuclear Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/icone17-75292.
Full textAbstract:
Among the Generation IV systems, Sodium Fast Reactors (SFR) are promising and benefit of considerable technological experience. However, the availability and the acceptability of the SFR are affected by the problems linked with the sodium-water reaction. One innovative solution to this problem is the replacement of the sodium in the secondary loops by an alternative liquid fluid. Among the fluids considered, lead-bismuth is at the moment being evaluated, liquid lead-bismuth has been considerably studied in the frame of the research program on Accelerator Driven Systems for transmutation applications. However, lead alloys are corrosive towards structural materials. The main parameters impacting the corrosion rate of Fe-Cr martensitic steels (considered as structural materials) are the nature of the steel (material side), the temperature, the liquid alloy velocity and the dissolved oxygen concentration (liquid alloy side). In this study, attention is focused on the behaviour of Fe-9Cr steels and more particularly T91 martensitic steel. It has been shown that in the case of Fe-Cr martensitic steels the corrosion process depends on the concentration of oxygen dissolved in Pb-Bi. - For an oxygen concentration lower than the one necessary for magnetite formation (approximately < 10−8 wt% at T ≈ 500 °C for Fe-9Cr steels), corrosion proceeds by dissolution of the steel. - For a higher oxygen content dissolved in Pb-Bi, corrosion proceeds by oxidation of the steel. These two corrosion processes have been experimentally and theoretically studied in CEA Saclay and also by other partners leading to some corrosion modelling in order to predict the life duration of these materials as well as their limits of utilisation. This study takes into account the two kinds of corrosion processes, dissolution and oxidation. In these two different processes, the lead alloy physico-chemical parameters are considered: the temperature and the liquid alloy velocity for both processes and the oxygen concentration for oxidation.
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Rao, P. M., N. Kasinathan, and S. E. Kannan. "Analysis of Sodium Fire in the Containment Building of Prototype Fast Breeder Reactor Under the Scenario of Core Disruptive Accident." In 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89566.
Full textAbstract:
The potential for sodium release to reactor containment building from reactor assembly during Core Disruptive Accident (CDA) in Fast Breeder Reactors (FBR) is an important safety issue with reference to the structural integrity of Reactor Containment Building (RCB). For Prototype Fast Breeder Reactor (PFBR), the estimated sodium release under a CDA of 100 MJ energy release is 350 kg. The ejected sodium reacts easily with air in RCB and causes temperature and pressure rise in the RCB. For estimating the severe thermal consequences in RCB, different modes of sodium fires like pool and spray fires were analyzed by using SOFIRE–II and NACOM sodium fire computer codes. Effects of important parameters like amount of sodium, area of pool, containment air volume and oxygen concentration have been investigated. A peak pressure rise of 7.32 kPa is predicted by SOFIRE II code for 350 kg sodium pool fire in 86,000 m3 RCB volume. Under sodium release as spray followed by unburnt sodium as pool fire mode analysis, the estimated pressure rise is 5.85 kPa in the RCB. In the mode of instantaneous combustion of sodium, the estimated peak pressure rise is 13 kPa.
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Vijayakumar, V., S. C. Chetal, K. Madhusoodanan, C. Paramasivan Pillai, M. Sakthivel, and Uma Seshadri. "Sodium and Steam Generator Leak Detection for Prototype Fast Breeder Reactor (PFBR)." In 12th International Conference on Nuclear Engineering. ASMEDC, 2004. http://dx.doi.org/10.1115/icone12-49362.
Full textAbstract:
Construction of Prototype Fast Breeder Reactor (PFBR) a 500 MWe pool type sodium cooled breeder reactor with MOX fuel has started at Kalpakkam. Instrumentation & Control (I&C) of PFBR is designed for safe, reliable and economic operation of the plant. Special feature of breeder reactors is sodium instrumentation. Leaks in sodium systems have the possibility of being exceptionally hazardous due to the reaction of liquid sodium with oxygen and water vapour in the air. In addition, leakage from primary systems can cause radioactive contamination. Potential regions of leakage are near welds and high stress areas. Sodium also reacts with concrete releasing hydrogen and leading to damage and loss of strength of concrete structures. Leaking sodium catches fire depending on its temperature. Sodium temperature in the plant ranges from 423 K at filling condition to 820 K at reactor nominal power operating condition. Leak detectors are provided on pipelines, tanks and other capacities. Sodium leak detection systems are designed to meet requirements of ASME section XI- division 3 which specifies that sodium leak at the rate of 100 g/h are to be detected in 20 h for air filled vaults and 250 h for inert vaults. Diverse leak detection methods are employed for active and non-active sodium equipment and pipes. For detection of water leaks into Sodium in steam generators, Hydrogen in Sodium Detectors (HSD) are used. Hydrogen in Argon Detectors (HAD) are used for sodium temperatures below 623 K as HSD is not effective below this temperature due to non-dissolution of hydrogen formed. Choice and challenges posed in implementation of above leak detection requirements are discussed in this paper.
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Morawitz, Falk. "Multilayered Narration in Electroacoustic Music Composition Using Nuclear Magnetic Resonance Data Sonification and Acousmatic Storytelling." In ICAD 2019: The 25th International Conference on Auditory Display. Newcastle upon Tyne, United Kingdom: Department of Computer and Information Sciences, Northumbria University, 2019. http://dx.doi.org/10.21785/icad2019.052.
Full textAbstract:
Nuclear magnetic resonance (NMR) spectroscopy is an analytical tool to determine the structure of chemical compounds. Unlike other spectroscopic methods, signals recorded using NMR spectrometers are frequently in a range of zero to 20000 Hz, making direct playback possible. As each type of molecule has, based on its structural features, distinct and predictable features in its NMR spectra, NMR data sonification can be used to create auditory ‘fingerprints’ of molecules. This paper describes the methodology of NMR data sonification of the nuclei nitrogen, phosphorous, and oxygen and analyses the sonification products of DNA and protein NMR data. The paper introduces On the Extinction of a Species, an acousmatic music composition combining NMR data sonification and voice narration. Ideas developed in electroacoustic composition, such as acousmatic storytelling and sound-based narration are presented and investigated for their use in sonification-based creative works.
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Butterman, Heidi C., and Marco J. Castaldi. "CO2 Enhanced Steam Gasification of Biomass Fuels." In 16th Annual North American Waste-to-Energy Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/nawtec16-1949.
Full textAbstract:
The current study involves an experimental investigation of the decomposition of various biomass feedstocks and their conversion to gaseous fuels such as hydrogen. The steam gasification process resulted in higher levels of H2 and CO for various CO2 input ratios. With increasing rates of CO2 introduced into the feed stream, enhanced char conversion and increased CO levels were observed. While CH4 evolution was present throughout the gasification process at consistently low concentrations, H2 evolution was at significantly higher levels though it was detected only at elevated gasification temperatures: above 500°C for the herbaceous and non-wood samples and above 650°C for the wood biomass fuels studied. The biomass feedstocks were studied through the use of Thermo Gravimetric Analysis (TGA), Gas Chromatography, Calorimetry, Atomic Absorption Spectrophotometry (AAS), and the Scanning Electron Microscope with Energy Dispersive X-Ray Analysis (SEM/EDX). The chemical composition of the various biomass fuels and their combustion and gasification ash residues, in addition to the mass decay and gaseous evolution behavior were investigated as a function of temperature. The thermal treatment of biomass fuels involves pyrolysis and gasification with combustion occurring at the higher temperatures. In the gasification environment, when combustion processes are occurring, gaseous components evolve from the fuel and react with oxygen either released from the biomass structure itself, or from the injected steam and CO2. These high temperature reactions are responsible for the enhanced burnout of the carbon (charcoal) structure that is produced during the low temperature pyrolytic breakdown of the biomass. Since the ligno-cellulosic biomass component typically found in U.S. MSW is greater than 50%, techniques to enhance the thermal treatment of biomass feedstocks can also aid in the processing of MSW. Gas evolution as a function of temperature was monitored for H2, CH4, CO2 and CO for several biomass fuels that included woods, grasses and other ligno-cellulosic samples. These included oak, sugar maple, poplar, spruce, white pine, Douglas fir, alfalfa, cordgrass, beachgrass, maple bark, pine needles, blue noble fir needles, pecan shells, almond shells, walnut shells, wheat straw, and green olive pit. The TGA mass decay curves showed similar behavior for the woods, grasses and agricultural residues, where most of the mass loss occurred before 500°C. Most feedstocks exhibited 2 constant mass steps though several exhibited a third with completed mass loss by 900°–1000°C. Two distinct mass decay regimes were found to correlate well with two distinct gas evolution regimes exhibited in the curves for CO, H2 and CH4. Most of the mass loss occurred during pyrolysis, with the remaining degradation to ash or char occurring in the high temperature gasification regime. One characteristic of biomass samples is the highly variable nature of the mineral composition. SEM/EDX analyses indicated high levels of potassium, magnesium and phosphorus in the ash residue. The devitrification and embrittlement of the quartz furnace and balance rods were attributed to the high mineral content of many of the biomass feedstocks, with the high alkaline oxide levels of the grasses being particularly destructive. While mineral content may exert a beneficial effect through enhanced char reactivity with the possibility for a more thorough processing of the feedstock, the potential for corrosion and slagging would necessitate the judicious selection and possible pretreatment of biomass fuels. A major advantage of thermal treatment through gasification prior to combustion is the ability to remove many of the corrosive volatiles and ash elements such as potassium, sodium and chlorine to avert damage to the process equipment.