- Refinement of the autoneutralization lifetimes of short lived states of SF6-
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Previous measurements of the autoneutralization lifetime of SF6- indicated there are multiple states (lifetimes) and that the distribution of states is controlled, at least in part, by the temperature of the SF6 molecules prior to electron capture.These measurements indicated the existence of a short lived state with a lifetime of the order of 2 μs.The experimental apparatus has been revised to confirm the existence of the short lived state and provide a more accurate measurement of the lifetime.
- Appelhans, A. D.,Delmore, J. E.
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- The standard molar enthalpy of formation at 298.15 K of VS1.043 by combustion calorimetry in fluorine
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The standard molar enthalpy of formation ΔfH0m of VS1.043 has been determined by fluorine-combustion calorimetry.The results obtained, -(230.3+/-2.2)kJ*mol-1 at 298.15 K and p0 = 101.325 kP
- Lewis, Brett M.,O'Hare, P. A. G.,Mukdeeprom, Pannee,Edwards, Jimmie G.
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- Standard molar enthalpy of formation at 298.15 K of the β-modification of molybdenum ditelluride
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Fluorine-combustion calorimetry of a high-purity sample of molybdenum ditelluride has yielded the standard molar enthalpy of formation: ΔfH0m(MoTe2, cr, β, 298.15 K) = -(84.2 +/- 4.6) kJ * mol-1.At 298.15 K, the enthalpy of the hypothetical β-to-α transition in MoTe2 is approximately -6 kJ * mol-1.The present result for ΔfH0m(MoTe2) has been combined with literature values for the decomposition pressures of MoTe2 to yield ΔfH0m(Mo3Te4, cr, 298.15 K) = -(185 +/- 10) kJ * mol-1.Our previously published ΔfH0m(TeF6) (Trans.Faraday Soc. 1966, 62, 558) has been revised slightly to -(1371.8 +/- 1.8) kJ * mol-1.
- O'Hare, P. A. G.,Hope, G. A.
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- The standard molar enthalpy of formation at 298.15 K of S2N+AsF6- by fluorine combustion calorimetry
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The energy of combustion of S2N+AsF6- in high-pressure fluorine has been measured calorimetrically.The only fluorine-containing gases formed in the combustion were SF6 and AsF5; both NF3 and AsF3 were sought, but not detected.The standard molar
- O'Hare, P. A. G.,Awere, Edward G.,Parsons, Simon,Passmore, Jack
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- F5SN(H)Xe+; a rare example of xenon bonded to sp 3-hybridized nitrogen; synthesis and structural characterization of [F5SN(H)Xe][AsF6]
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The salt [F5SN(H)Xe][AsF6] has been synthesized by the reaction of [F5SNH3][AsF6] with XeF 2 in anhydrous HF (aHF) and BrF5 solvents and by solvolysis of [F3S=NXeF][AsF6] in aHF. Both F 5SN(H)Xe+ and F5SNH3+ have been characterized by 129Xe, 19F, and 1H NMR spectroscopy in aHF (-20°C) and BrF5 (supercooled to -70°C). The yellow [F5SN(H)Xe][AsF6] salt was crystallized from aHF at -20°C and characterized by Raman spectroscopy at -45°C and by single-crystal X-ray diffraction at -173°C. The Xe-N bond length (2.069(4) A) of the F5SN(H)Xe+ cation is among the shortest Xe-N bonds presently known. The cation interacts with the AsF6- anion by means of a Xe...F-As bridge in which the Xe...F distance (2.634(3) A) is significantly less than the sum of the Xe and F van der Waals radii (3.63 A) and the AsF6 - anion is significantly distorted from Oh symmetry. The 19F and 129Xe NMR spectra established that the [F 5SN(H)Xe][AsF6] ion pair is dissociated in aHF and BrF5 solvents. The F5SN(H)Xe+ cation decomposes by HF solvolysis to F5SNH3+ and XeF 2, followed by solvolysis of F5SNH3+ to SF6 and NH4+. A minor decomposition channel leads to small quantities of F5SNF2. The colorless salt, [F5SNH3][AsF6], was synthesized by the HF solvolysis of F3S≡NAsF5 and was crystallized from aHF at -35°C. The salt was characterized by Raman spectroscopy at -160°C, and its unit cell parameters were determined by low-temperature X-ray diffraction. Electronic structure calculations using MP2 and DFT methods were used to calculate the gas-phase geometries, charges, bond orders, and valencies as well as the vibrational frequencies of F5SNH 3+ and F5SN(H)Xe+ and to aid in the assignment of their experimental vibrational frequencies. In addition to F 5TeN(H)Xe+, the F5SN(H)Xe+ cation provides the only other example of xenon bonded to an sp3-hybridized nitrogen center that has been synthesized and structurally characterized. These cations represent the strongest Xe-N bonds that are presently known.
- Smith, Gregory L.,Mercier, Helene P. A.,Schrobilgen, Gary J.
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p. 4173 - 4184
(2009/02/01)
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- Kinetics of sulfur oxide, sulfur fluoride, and sulfur oxyfluoride anions with atomic species at 298 and 500 K
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The rate constants and product-ion branching ratios for the reactions of sulfur dioxide (SO2-), sulfur fluoride (SF n-), and sulfur oxyfluoride anions (SOxF y-) with H, H2, N, N2, NO, and O have been measured in a selected-ion flow tube (SIFT). H atoms were generated through a microwave discharge on a H2/He mixture, whereas O atoms were created via N atoms titrated with NO, where the N had been created by a microwave discharge on N2. None of the ions reacted with H 2, N2 or NO; thus, the rate constants are -12 cm3 s-1. SOxFy - ions react with H by only fluorine-atom abstraction to form HF at 298 and 500 K. Successive F-atom removal does not occur at either temperature, and the rate constants show no temperature dependence over this limited range. SO2- and F- undergo associative detachment with H to form a neutral molecule and an electron. Theoretical calculations of the structures and energetics of HSO2- isomers were performed and showed that structural differences between the ionic and neutral HSO 2 species can account for at least part of the reactivity limitations in the SO2- + H reaction. All of the SOxF y- ions react with O; however, only SO2 - reacts with both N and O. SOxFy- reactions with N (SO2- excluded) have a rate constant limit of -11 cm3 s-1. The rate constants for the SOxFy- reactions with H and O are ≤25% of the collision rate constant, as seen previously in the reactions of these ions with O3, consistent with a kinetic bottleneck limiting the reactivity. The only exceptions are the reactions of SO2 - with N and O, which are much more efficient. Three pathways were observed with O atoms: F-atom exchange in the reactant ion, F- exchange in the reactant ion, and charge transfer to the O atom. No associative detachment was observed in the N- and O-atom reactions.
- Midey, Anthony J.,Viggian
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p. 1852 - 1859
(2008/10/09)
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- Pentafluoronitrosulfane, SF5NO2
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The synthesis of pentafluoronitrosulfane, SF5NO2, is accomplished either by reacting N(SF5)3 with NO 2 or by the photolysis of a SF5Br/NO2 mixture using diazo lamps. The product is purified by treatment with CsF and repeated trap-to-trap condensation. The solid compound melts at -78°C, and the extrapolated boiling point is 9°C. SF5NO2 is characterized by 19F, 15N NMR, IR, Raman, and UV spectroscopy as well as by mass spectrometry. The molecular structure of SF 5NO2 is determined by gas electron diffraction. The molecule possesses C2v symmetry with the NO2 group staggering the equatorial S-F bonds and an extremely long 1.903(7) A S-N bond. Calculated bond enthalpies depend strongly on the computational method: 159 (MP2/6-311G++(3df)) and 87 kJ mol-1 (B3LYP/6-311++G-(3df)). The experimental geometry and vibrational spectrum are reproduced reasonably well by quantum chemical calculations.
- Lu, Norman,Thrasher, Joseph S.,Von Ahsen, Stefan,Willner, Helge,Hnyk, Drahomir,Oberhammer, Heinz
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p. 1783 - 1788
(2008/10/09)
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- HONO solubility and heterogeneous reactivity on sulfuric acid surfaces
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The solubility of HONO in various wt% sulfuric acid solutions was measured. HONO becomes increasingly more soluble in high acid wt% solutions, probably resulting from the protonation of HONO to give H2ONO+, followed by dissociation and association to give NO+HSO4- (nitrosyl sulfuric acid). The reaction of HONO with HCl on 50, 60, 67, and 70 wt% sulfuric acid solutions was also studied. The measured uptake coefficients could not be explained simply by the occurrence of a bulk phase reaction, and a surface effect is found to contribute to the uptake. The reaction of HONO with HCl was measured on sulfuric acid particles, and a small reacto-diffusive length further supports a surface reaction. From extrapolating our measured uptake values to stratospheric conditions, the formation of ClNO from the heterogeneous reaction of HONO and HCl is concluded to be an insignificant process in the volcanically unperturbed stratosphere.
- Longfellow,Imamura,Ravishankara,Hanson
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p. 3323 - 3332
(2007/10/03)
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- Low temperature fluorination of some non-metals and non-metal compounds with fluorine
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Low temperature fluorination with elemental fluorine of elemental phosphorus, sulphur, silicon, amorphous carbon and phosphorus trichloride, phosphorus pentoxide, triphenylphosphine, hexafluorodisilane, hexachlorodisilane, hexabromodisilane, tetrasulphur tetranitride, sulphur dioxide, thionyl chloride and sulphuryl chloride has been carried out in freon-11 medium.The corresponding fluoro compounds have been isolated in near quanititative yields, purified by low temperature fractional condensation and characterised by IR spectroscopy and elemental analysis.
- Padma, D K,Kalbandkeri, R G,Suresh, B S,Bhat, V Subrahmanya
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p. 172 - 176
(2007/10/02)
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- Attempted Synthesis of Osmium(VI) and Iridium(VI) Thiofluorides; the Preparation of OsF5.SF4 and IrF5.SF4
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The interaction of OsF4 or IrF4 with ZnS or B2S3 at elevated temperature yields the adducts OsF5.SF4 and IrF5.SF4 rather than the trasition-metal thiofluorides.Infrared and X-ray powder diffraction studies indicate that the adducts have contributions to the bonding from the ionic formulations +- and +- and there is also (19)F n.m.r. evidence for the latter in solution in anhydrous HF.
- Holloway, John. H,Rook, John
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p. 2285 - 2288
(2007/10/02)
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- Lewis acid induced intramolecular redox reactions of difluoramino compounds
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It is shown that strong Lewis acids, such as AsF5 or SbF5, which are good fluoride ion acceptors, strongly catalyze an intramolecular redox reaction of difluoramino compounds, such as CF3NF2, SF5NF2, ClNF2, CF3ONF2, and SF5ONF2. In the ClNF2-AsF5 system a thermally unstable intermediate is formed at -78°C, which on the basis of its Raman spectra is the fluorine-bridged donor-acceptor adduct ClNF2-AsF5. The nature of the final decomposition products can be rationalized in terms of their stability. In connection with the low-temperature Raman studies, an unidentified, unstable, blue-green species was observed that gives rise to a resonance Raman spectrum with v = 177 cm-1 and that is also formed from Cl3+AsF6- and excess Cl2. For NF2Cl, 14N-19F spin-spin coupling was observed in its 19F NMR spectrum.
- Christe, Karl O.,Wilson, William W.,Schack, Carl J.,Wilson, Richard D.
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p. 303 - 307
(2008/10/08)
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- Ion Chemistry and Electron Affinity of WF6
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The rate coefficients and branching ratios have been measured for the reactions of WF6 with F(-),Cl(1-), Br(1-), I(1-),CN(1-),NO3(1-), NO2(1-),SF5(1-) and SF6(1-).WF6 was found to react rapidly with these ions.Three channels were observed: asociation, cha
- Viggiano, A. A.,Paulson, John, F.,Dale, Fred,Henchman, Michael,Adams,N. G.,Smith, D.
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p. 2264 - 2267
(2007/10/02)
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- INTERACTION BETWEEN URANIUM PENTAFLUORIDE AND THE PENTAFLUORIDES OF VANADIUM, ARSENIC, NIOBIUM, TANTALUM, AND BISMUTH, AND THE TETRAFLUORIDE OF SULPHUR
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The interaction of UF5 with SF4, SF4O, and some Lewis-acid pentafluorides of various strengths has been studied.In anhydrous HF solutions, SF4 was shown to yield an adduct of composition 3UF5*SF4 in which both ionic and fluorine-bridged species are present.The pentafluorides of arsenic, tantalum, and niobium combine with UF5 to give adducts of composition 1.5 UF5*AsF5, UF5*2TaF5, and UF5*2NbF5, respectively.The arsenic derivative is stable at room temperature only under a pressure of AsF5, whereas the tantalum and niobium adducts decompose at higher temperature forming UF5*TaF5 and UF5*NbF5, respectively.Vibrational spectroscopic study of the pentafluoride adducts of UF5 has shown that they consist of covalent fluorine-bridged species.Uranium pentafluoride is fluorinated at room temperature by VF5 and by BiF5 in anhydrous HF.
- Holloway, John H.,Staunton, Garry M.,Rediess, Klaus,Bougon, Roland,Brown, David
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p. 2163 - 2166
(2007/10/02)
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- The Reaction of S2NAsF6 with Halogens: Preparation and X-Ray Crystal Structure of Bis(difluorothio)nitronium Hexafluoroarsenate(V), (SF2)2NAsF6; Preparation of (SBr)2NAsF6, and Vibrational Spectrum and Normal-co-ordinate Analysis of the (SX)2N+ (X=Cl or Br) Cations
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Solutions of S2NAsF6 in liquid SO2 react with elemental chlorine and bromine yielding (SX)2NAsF6 (X=Cl or Br), essentially quantitatively.No reaction was detected with iodine.The vibrational spectrum of (SBr)2N+ was similar to that of (SCl)2N+ of known structure, implying a similar structure for the bromine derivative.This conclusion was supported by a normal-co-ordinate analysis of (SX)2N+.The analysis was consistent with some positive interaction between the halogen atoms in (SX)2N+, possibly accounting for the cis planar geometry of these cations.Attempts to prepare (SF)2NAsF6 were unsuccessful.However, (SF2)2NAsF6 was synthesised by the reaction of S2NAsF6 and XeF2 in liquid SO2F2, essentially quantitatively.The structure of (SF2)2NAsF6 was determined by X-ray diffraction.The crystals are orthorhombic with a=14.909(1), b=9.843(4), c=12.113(1) Angstroem, and Z=8.The structure was refined in space group Pbca to a conventional R factor of 0.076 for 902 independent reflections with I>2?(I).It consists of discrete (SF2)2N+ and AsF6- with some cation-anion interactions.The (SF2)2N+ cation has approximate C2γ symmetry with essentially eclipsed fluorine-sulphur bonds as viewed along the sulphur-sulphur axis.The average S-N and S-F distances are 1.551(10) and 1.523(8) Angstroem, and the average FSF and FSN bond angles are 94.0(5) and 100.2(6) deg.The SNS bond angle is 121.1(6) deg.The vibrational spectrum of (SF2)2NAsF6 is reported.
- Brooks, Wendell V. F.,MacLean, Gregory K.,Passmore, Jack,White, Peter S.,Wong, Chi-Ming
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p. 1961 - 1968
(2007/10/02)
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- Novel sulfur-nitrogen-fluorine compounds. Synthesis and properties of SF5NClF, SF5NHF, and FN=SF4 and the molecular structure and vibrational analysis of FN=SF4
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Pentafluoro(fluorochloroamido)sulfur, SF5NFCl, can be synthesized from NSF3 by low-temperature reaction with ClF, followed by reaction with fluorine. Reduction of SF5NClF with mercury in trifluoroacetic acid forms (fluoroimido)pentafluorosulfur, SF5NHF, in high yield. Dehydrofluorination of SF5NFH with KF results in (fluoroimido)tetrafluorosulfur, FN=SF4. The imine is an unusual pentacoordinate molecule which does not undergo positional exchange of the sulfur fluorines according to 19F NMR. A complete vibrational analysis of FN=SF4 based on Cs symmetry has been carried out and found to be in good agreement with the related molecules OSF4, CH2=SF4, and SF4. The gas-phase structure was determined by joint analysis of electron diffraction and microwave spectroscopic data. The structure contains a relatively long S=N bond, short N-F bond, and a large difference in the nonequivalent axial S-F bonds.
- DesMarteau, Darryl D.,Eysel, Hans H.,Oberhammer, Heinz,Günther, Horst
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p. 1607 - 1616
(2008/10/08)
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- The Kinetics and the Mechanism of the Thermal Reaction between Sulfurtetrafluoride and Fluorine
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The kinetics of the thermal reaction between SF4 and F2 has been investigated between -2.4 deg C and +24.0 deg C, SF6 and very small amounts of S2F10 being the only products.The reaction is a chain reaction of medium length.Total pressure and surface have only insignificant influence.The reaction rate follows the equation: (equation).The results can be represented by the following mechanism: SF4 + F2 = SF5 + F (1) F + SF4 = SF5 (2) SF5 + F2 = SF6 + F (3) SF5 + F = SF6 (4a) SF5 + SF5 = S2F10 (4b).Under the experimental conditions less than 15percent of the SF5 radicals are consumed by r (4b).Therefore (equation), (equation).Oxygen inhibits the reaction eliminating the SF5 radicals, the final products being now SF5O3SF5 and SF6.From the data obtained in the experiments with high oxygen pressures the rate constant of the primary process and the chain length (ν) are determined. (equation); (equation).E = 10.8 +/- 0.7 kcal, E1 = 11.9 +/- 0.6 kcal and E4 ca. 0.E2 = 5.0 +/- 2.0 kcal (estimated value) and E3 = 4.7 +/- 2.5 kcal. - Key words: Kinetics, Sulfurtetrafluoride, Fluorine
- Gonzalez, Alicia Cristina,Schumacher, Hans Joachim
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p. 1381 - 1385
(2007/10/02)
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- Die Kinetik der thermischen Reaktion zwischen Schwefeltetrafluorid und Fluor in Gegenwart von Sauerstoff
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The kinetics of the thermal reaction between SF4 and F2 in the presence of O2 has been investigated between -14 deg C and +7 deg C.The reaction is homogeneous and the final products are SF6 and SF5O3SF5.An increase of the O2 pressure favours the formation of the trioxide and reduces the SF6 formation and the consumption of F2.The rate of SF4 consumption reaches in the presence of several 100 Torr O2 a minimum and the relation / a maximum.The reaction itself is of 2nd order. .For O2 > 400 Torr results k = (9.1 +/- 0.2)*1E7exp lMol-1s-1. - Keywords: Kinetics / Sulfurtetrafluoride / Fluorine / Oxygen
- Gonzalez, Alicia C.,Schumacher, Hans J.
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p. 167 - 178
(2007/10/02)
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- Negative ion-uranium hexafluoride charge transfer reactions
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The flowing afterglow technique has been used to study the process of charge transfer from selected negative ions (F-, Cl-, Br-, I-, SF6-) to UF6.The sole ionic product in all cases was observed to be
- Streit, Gerald E.,Newton, T. W.
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p. 3178 - 3182
(2007/10/02)
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- Some reactions of pentafluorosulfur hypofluorite and trifluoromethyl hypofluorite
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The reaction of peutafluorosulfur hypofluorite with sulfur dioxide in the liquid phase gives SF5OSO2F. Pentafluorosulfur hypofluorite reacts with sulfur tetrafluoride to give SF5OSF5, SF5OOSF5, and SF5OSF4OSF5, while a similar reaction in the presence of oxygen gives SF5OSF4OOSF5 and SF5OSF4OOSF4OSF5 as additional products. These new peroxides react with benzene to give C6H5OSF4OSF5. The reaction of trifluoromethyl hypofluorite with sulfur tetrafluoride gives CF3OSF5 as the only product. Trifluoromethyl hypofluorite, sulfur tetrafluoride, and oxygen react to give CF3OSF4OSF5, CF3OSF4OOSF5, and a compound believed to be CF3OSF4OOSF4OCF3. A reaction scheme which accounts for these products is proposed.
- Pass,Roberts
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p. 1016 - 1019
(2008/10/08)
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