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1.
The hydrothermal reactions of vanadium oxide starting materials with divalent transition metal cations in the presence of nitrogen donor chelating ligands yield the bimetallic cluster complexes with the formulae [{Cd(phen 2) 2V 4O 12]·5H 2O (1) and [Ni(phen) 3] 2[V 4O 12]·17.5H 2O (2). Crystal data: C 48H 52Cd 2N 8O 22V 4 (1), triclinic.
a=10.3366(10), b=11.320(3), c=13.268(3) Å, =103.888(17)°, β=92.256(15)°, γ=107.444(14)°, Z=1; C 72H 131N 12Ni 2O 29.5V 4 (2), triclinic.
a=12.305(3), b=13.172(6), c=15.133(4), =79.05(3)°, β=76.09(2)°, γ=74.66(3)°, Z=1. Data were collected on a Siemens P4 four-circle diffractometer at 293 K in the range 1.59° <θ<26.02° and 2.01°<θ<25.01° using the ω-scan technique, respectively. The structure of 1 consists of a [V 4O 12] 4− cluster covalently attached to two {Cd(phen) 2} 2+ fragments, in which the [V 4O 12] 4− cluster adopts a chair-like configuration. In the structure of 2, the [V 4O 12] 4− cluster is isolated. And the complex formed a layer structure via hydrogen bonds between the [V 4O 12] 4− unit and crystallization water molecules. 相似文献
2.
The syntheses and structural determination of Nd III and Er III complexes with nitrilotriacetic acid (nta) were reported in this paper. Their crystal and molecular structures and compositions were determined by single-crystal X-ray structure analyses and elemental analyses, respectively. The crystal of K 3[Nd III(nta) 2(H 2O)]·6H 2O complex belongs to monoclinic crystal system and C2/ c space group. The crystal data are as follows: a=1.5490(11) nm, b=1.3028(9) nm, c=2.6237(18) nm, β=96.803(10)°, V=5.257(6) nm 3, Z=8, M=763.89, Dc=1.930 g cm −3, μ=2.535 mm −1 and F(000)=3048. The final R1 and wR1 are 0.0390 and 0.0703 for 4501 ( I>2σ( I)) unique reflections, R2 and wR2 are 0.0758 and 0.0783 for all 10474 reflections, respectively. The Nd IIIN 2O 7 part in the [Nd III(nta) 2(H 2O)] 3− complex anion has a pseudo-monocapped square antiprismatic nine-coordinate structure in which the eight coordinate atoms (two N and six O) are from the two nta ligands and a water molecule coordinate to the central Nd III ion directly. The crystal of the K 3[Er III(nta) 2(H 2O)]·5H 2O complex also belongs to monoclinic crystal system and C2/ c space group. The crystal data are as follows: a=1.5343(5) nm, b=1.2880(4) nm, c=2.6154(8) nm, b=96.033(5)°, V=5.140(3) nm 3, Z=8, M=768.89, Dc=1.987 g cm −3, μ=3.833 mm −1 and F(000)=3032. The final R1 and wR1 are 0.0321 and 0.0671 for 4445 ( I>2σ( I)) unique reflections, R2 and wR2 are 0.0432 and 0.0699 for all 10207 reflections, respectively. The Er IIIN 2O 7 part in the [Er III(nta) 2(H 2O)] 3− complex anion has the same structure as Nd IIIN 2O 7 part in which the eight coordinate atoms (two N and six O) are from the two nta ligands and a water molecule coordinate to the central Nd III ion directly. 相似文献
3.
The molecular structure and conformational properties of O=C(N=S(O)F 2) 2 (carbonylbisimidosulfuryl fluoride) were determined by gas electron diffraction (GED) and quantumchemical calculations (HF/3-21G* and B3LYP/6-31G*). The analysis of the GED intensities resulted in a mixture of 76(12)% syn– syn and 24(12)% syn– anti conformer (Δ H0= H0( syn– anti)− H0( syn– syn)=1.11(32) kcal mol −1) which is in agreement with the interpretation of the IR spectra (68(5)% syn– syn and 32(5)% syn– anti, Δ H0=0.87(11) kcal mol −1). syn and anti describe the orientation of the S=N bonds relative to the C=O bond. In both conformers the S=O bonds of the two N=S(O)F 2 groups are trans to the C–N bonds. According to the theoretical calculations, structures with cis orientation of an S=O bond with respect to a C–N bond do not correspond to minima on the energy hyperface. The HF/3-21G* approximation predicts preference of the syn– anti structure (Δ E=−0.11 kcal mol −1) and the B3LYP/6-31G* method results in an energy difference (Δ E=1.85 kcal mol −1) which is slightly larger than the experimental values. The following geometric parameters for the O=C(N=S) 2 skeleton were derived ( ra values with 3 σ uncertainties): C=O 1.193 (9) Å, C–N 1.365 (9) Å, S=N 1.466 (5) Å, O=C–N 125.1 (6)° and C–N=S 125.3 (10)°. The geometric parameters are reproduced satisfactorily by the HF/3-21G* approximation, except for the C–N=S angle which is too large by ca. 6°. The B3LYP method predicts all bonds to be too long by 0.02–0.05 Å and the C–N=S angle to be too small by ca. 4°. 相似文献
4.
This work presents chemical modeling of solubilities of metal sulfates in aqueous solutions of sulfuric acid at high temperatures. Calculations were compared with experimental solubility measurements of hematite (Fe 2O 3) in aqueous ternary and quaternary systems of H 2SO 4, MgSO 4 and Al 2(SO 4) 3 at high temperatures. A hybrid model of ion-association and electrolyte non-random two liquid (ENRTL) theory was employed to fit solubility data in three ternary systems H 2SO 4–MgSO 4–H 2O, H 2SO 4–Al 2(SO 4) 3–H 2O at 235–270 °C and H 2SO 4–Fe 2(SO 4) 3–H 2O at 150–270 °C. Employing the Aspen Plus™ property program, the electrolyte NRTL local composition model was used for calculating activity coefficients of the ions Al 3+, Mg 2+ Fe 3+ and SO 42−, HSO 4−, OH −, H 3O +, respectively, as well as molecular species. The solid phases were hydronium alunite (H 3O)Al 3(SO 4) 2(OH) 6, hematite Fe 2O 3 and magnesium sulfate monohydrate (MgSO 4)·H 2O which were employed as constraint precipitation solids in calculating the metal sulfate solubilities. A correlation for the equilibrium constants of the association reactions of complex species versus temperature was implemented. Based on the maximum-likelihood principle, the binary interaction energy parameters for the ionic species as well as the coefficients for equilibrium constants of the reactions were obtained simultaneously using the solubility data of the ternary systems. Following that, the solubilities of metal sulfates in the quaternary systems H 2SO 4–Fe 2(SO 4) 3–MgSO 4–H 2O, H 2SO 4–Fe 2(SO 4) 3–Al 2(SO 4) 3–H 2O at 250 °C and H 2SO 4–Al 2(SO 4) 3–MgSO 4–H 2O at 230–270 °C were predicted. The calculated results were in excellent agreement with the experimental data. 相似文献
5.
The compound [Zn(H 2O) 4] 2[H 2As 6V 15O 42(H 2O)]·2H 2O (1) has been synthesized and characterized by elemental analysis, IR, ESR, magnetic measurement, third-order nonlinear property study and single crystal X-ray diffraction analysis. The compound 1 crystallizes in trigonal space group R3, a= b=12.0601(17) Å, c=33.970(7) Å, γ=120°, V=4278.8(12) Å 3, Z=3 and R1( wR2)=0.0512 (0.1171). The crystal structure is constructed from [H 2As 6V 15O 42(H 2O)] 4− anions and [Zn(H 2O) 4] 2+ cations linked through hydrogen bonds into a network. The [H 2As 6V 15O 42(H 2O)] 6− cluster consists of 15 VO 5 square pyramids linked by three As 2O 5 handle-like units. 相似文献
6.
The effects of doping of Co 3O 4with MgO (0.4–6 mol%) and V 2O 5 (0.20–0.75 mol%) on its surface and catalytic properties were investigated using nitrogen adsorption at −196°C and decomposition of H 2O 2 at 30–50°C. Pure and doped samples were prepared by thermal decomposition in air at 500–900°C, of pure basic cobalt carbonate and basic carbonate treated with different proportions of magnesium nitrate and ammonium vanadate. The results revealed that, V 2O 5 doping followed by precalcination at 500–900°C did not much modify the specific surface area of the treated Co 3O 4 solid. Treatment of Co 3O 4 with MgO at 500–900°C resulted in a significant increase in the specific surface area of cobaltic oxide. The catalytic activity in H 2O 2 decomposition, of Co 3O 4 was found to suffer a considerable increase by treatment with MgO. The maximum increase in the catalytic reaction rate constant ( k) measured at 40°C on Co 3O 4 due to doping with 3 mol% MgO attained 218, 590 and 275% for the catalysts precalcined at 500, 700 and 900°C, respectively. V 2O 5-doping of Co 3O 4 brought about a significant progressive decrease in its catalytic activity. The maximum decrease in the reaction rate constant measured at 40°C over the 0.75 mol% V 2O 5-doped Co 3O 4 solid attained 68 and 93% for the catalyst samples precalcined at 500 and 900°C, respectively. The doping process did not modify the activation energy of the catalyzed reaction but much modified the concentration of catalytically active constituents without changing their energetic nature. MgO-doping increased the concentration of CO 3+–CO 2+ ion pairs and created Mg 2+–CO 3+ ion pairs increasing thus the number of active constituents involved in the catalytic decomposition of H 2O 2. V 2O 5-doping exerted an opposite effect via decreasing the number of CO 3+–CO 2+ ion pairs besides the possible formation of cobalt vanadate. 相似文献
7.
The rate constants, k1 and k2 for the reactions of C 2F 5OC(O)H and n-C 3F 7OC(O)H with OH radicals were measured using an FT-IR technique at 253–328 K. k1 and k2 were determined as (9.24 ± 1.33) × 10 −13 exp[−(1230 ± 40)/ T] and (1.41 ± 0.26) × 10 −12 exp[−(1260 ± 50)/ T] cm 3 molecule −1 s −1. The random errors reported are ±2 σ, and potential systematic errors of 10% could add to the k1 and k2. The atmospheric lifetimes of C 2F 5OC(O)H and n-C 3F 7OC(O)H with respect to reaction with OH radicals were estimated at 3.6 and 2.6 years, respectively. 相似文献
8.
The second-order rate constants of gas-phase Lu( 2D 3/2) with O 2, N 2O and CO 2 from 348 to 573 K are reported. In all cases, the reactions are relatively fast with small barriers. The disappearance rates are independent of total pressure indicating bimolecular abstraction processes. The bimolecular rate constants (in molecule −1 cm 3 s −1) are described in Arrhenius form by k(O 2)=(2.3±0.4)×10 −10exp(−3.1±0.7 kJmol −1/ RT), k(N 2O)=(2.2±0.4)×10 −10exp(−7.1±0.8 kJmol −1/ RT), k(CO 2)=(2.0±0.6)×10 −10exp(−7.6±1.3 kJmol −1/ RT), where the uncertainties are ±2σ. 相似文献
9.
The crystal structure of N-(2-hydroxy-5-chlorophenyl) salicylaldimine (C 13H 10NO 2Cl) was determined by X-ray analysis. It crystallizes orthorhombic space group P2 12 12 1 with a=12.967(2) Å, b=14.438(3) Å, c=6.231(3) Å, V=1166.5(6) Å 3, Z=4, Dc=1.41 g cm −3 and μ(MoK )=0.315 mm −1. The title compound is thermochromic and the molecule is nearly planar. Both tautomeric forms (keto and enol forms in 68(3) and 32(3)%, respectively) are present in the solid state. The molecules contain strong intramolecular hydrogen bonds, N1–H1O1/O2 (2.515(1) and 2.581(2) Å) for the keto form and O1–H01N1 for the enol one. There is also strong intermolecular O2–HO1 hydrogen bonding (2.599(2) Å) between neighbouring molecules. Minimum energy conformations AM1 were calculated as a function of the three torsion angles, θ1(N1–C7–C6–C5), θ2(C8–N1–C7–C6) and θ3(C9–C8–N1–C7), varied every 10°. Although the molecule is nearly planar, the AM1 optimized geometry of the title compound is not planar. The non-planar conformation of the title compound corresponding to the optimized X-ray structure is the most stable conformation in all calculations. 相似文献
10.
The collisional quenching of electronically excited germanium atoms, Ge[4p 2( 1S 0)], 2.029 eV above the 4p 2( 3P 0) ground state, has been investigated by time-resolved atomic resonance absorption spectroscopy in the ultraviolet at λ = 274.04 nm [4d( 1P 10) ← 4p 2( 1S 0)]. In contrast to previous investigations using the ‘single-shot mode’ at high energy, Ge( 1S 0) has been generated by the repetitive pulsed irradiation of Ge(CH 3) 4 in the presence of excess helium gas and added gases in a slow flow system, kinetically equivalent to a static system. This technique was originally developed for the study of Ge[4p 2( 1D 2)] which had eluded direct quantitative kinetic study until recently. Absolute second-order rate constants obtained using signal averaging techniques from data capture of total digitised atomic decay profiles are reported for the removal of Ge( 1S 0) with the following gases ( kR in cm 3 molecule −1 s −1, 300 K): Xe, 7.1 ± 0.4 × 10 −13; N 2, 4.7 ± 0.6 × 10 −12; O 2, 3.6 ± 0.9 × 10 −11; NO, 1.5 ± 0.3 × 10 −11; CO, 3.4 ± 0.5 × 10 −12; N 2O, 4.5 ± 0.5 × 10 −12; CO 2, 1.1 ± 0.3 × 10 −11; CH 4, 1.7 ± 0.2 × 10 −11; CF 4, 4.8 ± 0.3 × 10 −12; SF 6, 9.5 ± 1.0 × 10 −13; C 2H 4, 3.3 ± 0.1 × 10 −10; C 2H 2, 2.9 ± 0.2 × 10 −10; Ge(CH 3) 4, 5.4 ± 0.2 × 10 −11. The results are compared with previous data for Ge( 1S 0) derived in the single-shot mode where there is general agreement though with some exceptions which are discussed. The present data are also compared with analogous quenching rate data for the collisional removal of the lower lying Ge[4p 2( 1D 2)] state (0.883 eV), also characterized by signal averaging methods similar to that described here. 相似文献
11.
Hydrated strontium borate, SrB 4O 7·3H 2O, has been synthesized and characterized by XRD, FT-IR, DTA-TG and chemical analysis. The molar enthalpy of solution of SrB 4O 7·3H 2O in 1 mol dm −3 HCl(aq) was measured to be (21.15 ± 0.29) kJ mol −1. With incorporation of the previously determined enthalpies of solution of Sr(OH) 2·8H 2O(s) in [HCl(aq) + H 3BO 3(aq)] and H 3BO 3 in HCl(aq), and the enthalpies of formation of H 2O(l), Sr(OH) 2·8H 2O(s) and H 3BO 3(s), the enthalpy of formation of SrB 4O 7·3H 2O was found to be −(4286.7 ± 3.3) kJ mol −1. 相似文献
12.
Hydrothermal reaction of copper(II) acetate, 2,2′-bipyridine (bipy) and NH 4VO 3 at 170 °C lead to a new layered polyoxovanadate with organically covalent-bonded copper(II) complex, Cu 2(bipy) 2V 6O 17 (1). Cu 2(bipy) 2V 6O 17 (1) is a new copper(II) vanadium(V) oxide featuring a new layered architecture, in which the V 2O 7 dimeric units and the cyclic tetranuclear V 4O 12 cluster units are interconnected via corner sharing into a unique one-dimensional {V 6O 17} 4− anionic chain, such chains are further bridged by {Cu(bipy)} 2+ complex cations into a 010 organic–inorganic hybrid layer. 相似文献
13.
We have applied cavity ring-down spectroscopy to a kinetic study of the reaction of NO 3 with CH 2I 2 in 25–100 Torr of N 2 diluent at 298 K. The rate constant of reaction of NO 3 + CH 2I 2 is determined to be (4.0 ± 1.2) × 10 −13 cm 3 molecule −1 s −1 in 100 Torr of N 2 diluent at 298 K. The rate constant increases with increasing pressure of buffer gas below 100 Torr. The reaction of CH 2I 2 with NO 3 has the potential importance at nighttime in the atmosphere. 相似文献
14.
The solid–solid interactions between pure and alumina-doped cobalt and ferric oxides have been investigated using DTA, IR and XRD techniques. Equimolar proportions of basic cobalt carbonate and ferric oxide and different amounts of aluminum nitrate were added as dopant substrate. The amounts of dopant were 0.75, 1.5, 3.0 and 4.5 mol% Al 2O 3. The results obtained revealed that solid–solid interaction between Fe2O3 and Co3O4 takes place at temperatures starting from 700°C to produce cobalt ferrite. The degree of propagation of this reaction increases progressively as a function of precalcination temperature and Al2O3-doping of the reacting solids. However, the heating of pure mixed solids at 1000°C for 6 h. was not sufficient to effect the complete conversion of the reacting solids into CoFe2O4, while the addition of a small amount of Al2O3 (1.5 mol%) to ferric/cobalt mixed solids followed by precalcination at 1000°C for 6 h conducted the complete conversion of the reacting solids into cobalt ferrite. The heat treatment of pure and the 0.75 mol%-doped solids at 900 and 1000°C effected the disappearance of most of IR transmission bands of the free oxides with subsequent appearance of new bands characteristic for the CoFe2O4 structure. An increase in the amount of Al2O3 added from 1.5–4.5 mol% to the mixed solids precalcined at 1000°C led to the disappearance of all bands of free oxides and appearance of all bands of cobalt ferrite. The promotion effect of Al2O3 in cobalt ferrite formation was attributed to an effective increase in the mobility of the various reacting cations. The activation energy of formation (ΔE) of CoFe2O4 phase was determined for pure and doped solids. The computed values of ΔE were, respectively, 99.6, 87.8, 71.9, 64.7 and 48.7 kJ mol−1 for the pure solid and those treated with 0.75, 1.5, 3 and 4.5 mol% Al2O3. 相似文献
15.
A series of γ-Al 2O 3 samples modified with various contents of sulfate (0–15 wt.%) and calcined at different temperatures (350–750 °C) were prepared by an impregnation method and physically admixed with CuO–ZnO–Al 2O 3 methanol synthesis catalyst to form hybrid catalysts. The direct synthesis of dimethyl ether (DME) from syngas was carried out over the prepared hybrid catalysts under pressurized fixed-bed continuous flow conditions. The results revealed that the catalytic activity of SO 42−/γ-Al 2O 3 for methanol dehydration increased significantly when the content of sulfate increased to 10 wt.%, resulting in the increase in both DME selectivity and CO conversion. However, when the content of sulfate of SO 42−/γ-Al 2O 3 was further increased to 15 wt.%, the activity for methanol dehydration was increased, and the selectivity for DME decreased slightly as reflected in the increased formation of byproducts like hydrocarbons and CO 2. On the other hand, when the calcination temperature of SO 42−/γ-Al 2O 3 increased from 350 °C to 550 °C, both the CO conversion and the DME selectivity increased gradually, accompanied with the decreased formation of CO 2. Nevertheless, a further increase in calcination temperature to 750 °C remarkably decreased the catalytic activity of SO 42−/γ-Al 2O 3 for methanol dehydration, resulting in the significant decline in both DME selectivity and CO conversion. The hybrid catalyst containing the SO 42−/γ-Al 2O 3 with 10 wt.% sulfate and calcined at 550 °C exhibited the highest selectivity and yield for the synthesis of DME. 相似文献
16.
The effects of calcination temperature and doping with K 2O on solid–solid interactions and physicochemical properties of NiO/Fe 2O 3 system were investigated using TG, DTA and XRD techniques. The amounts of potassium, expressed as mol% K 2O were 0.62, 1.23, 2.44 and 4.26. The pure and variously doped mixed solids were thermally treated at 300, 500, 750, 900 and 1000 °C. The catalytic activity was determined for each solid in H 2O 2 decomposition reaction at 30–50 °C. The results obtained showed that the doping process much affected the degree of crystallinity of both NiO and Fe 2O 3 phases detected for all solids calcined at 300 and 500 °C. Fe 2O 3 interacted readily with NiO at temperature starting from 700 °C producing crystalline NiFe 2O 4 phase. The degree of reaction propagation increased with increasing calcination temperature. The completion of this reaction required a prolonged heating at temperature >900 °C. K 2O-doping stimulates the ferrite formation to an extent proportional to its amount added. The stimulation effect of potassium was evidenced by following up the change in the peak height of certain diffraction lines characteristic NiO, Fe 2O 3, NiFe 2O 4 phases located at “d” spacing 2.08, 2.69 and 2.95 Å, respectively. The change of peak height of the diffraction lines at 2.95 Å as a function of firing temperature of pure and doped mixed solids enabled the calculation of the activation energy (Δ E) of the ferrite formation. The computed Δ E values were 120, 80, 49, 36 and 25 kJ mol −1 for pure and variously doped solids, respectively. The decrease in Δ E value of NiFe 2O 4 formation as a function of dopant added was not only attributed to an effective increase in the mobility of reacting cations but also to the formation of potassium ferrite. The calcination temperature and doping with K 2O much affected the catalytic activity of the system under investigation. 相似文献
17.
Solid acids – NiSO 4/Al 2O 3, Fe 2(SO 4) 3/Al 2O 3 and TiO 2/SO 42− – appeared to be effective catalysts for the acid catalyzed synthesis of methyl ester of trifluoropyruvic acid. They are active at 150–180 °C. 相似文献
18.
Medium-resolution spectra of the N 2 b 1Π u-X 1Σ g+ band system were recorded by 1 + 1 multiphoton ionization. In the spectra we found different linewidths for transitions to different vibrational levels in the b 1Π u state: Δν 0 = 0.50 ± 0.05 cm −1, Δν 1 = 0.28 ± 0.02 cm −1, Δν 2 = 0.65 ± 0.06 cm −1, Δν 3 = 3.2 ± 0.5 cm −1, Δν 4 = 0.60 ± 0.07 cm −1, and Δν 5 = 0.28 ± 0.02 cm −1. From these linewidths, predissociation lifetimes τ ν were obtained: τ 0 = 16 ± 3 ps, τ 1 > 150 ps, τ 2 = 10 ± 2 ps, τ 3 = 1.6 ± 0.3 ps, τ 4 = 9 ± 2 ps, and τ 5 > 150 ps. Band origins and rotational constants for the b 1Π uν = 0 and 1 levels were determined for the 14N 2 and 14N 15N molecules. 相似文献
19.
NH 2 profiles were measured in a discharge flow reactor at ambient temperature by monitoring reactants and products with an electron impact mass spectrometer. At the low pressures used (0.7 and 1.0 mbar) the gas-phase self-reaction is dominated by a ‘bimolecular’ H 2-eliminating exit channel with a rate coefficient of k3b(300 K) = (1.3 ± 0.5) × 10 −12 cm 3 molecule −1 s −1 and leading to N 2H 2 + H 2 or NNH 2 + H 2. Although the wall loss for NH 2 radicals is relatively small ( kw ≈ 6–14 s −1), the contribution to the overall NH 2 decay is important due to the relatively slow gas-phase reaction. The heterogeneous reaction yields N 2H 4 molecules. 相似文献
20.
The bimetallic [Pt(NH 3) 4] 2[W(CN) 8][NO 3]·2H 2O is characterised by single-crystal X-ray diffraction [S.G. P2 1/ m(11), a=8.0418(7), b=19.122(2), c=9.0812(6) Å, Z=2]. All platinum centres have the square-plane D4h geometry with average dimensions Pt(1)–N 2.042(2) and Pt(2)–N 2.037(10) Å. The octacyanotungstate anion has the square-antiprismatic D4d configuration with average dimensions W(1)–C 2.164(13), C–N 1.140(12), W(1)–N 3.303(5) Å. The structure exhibits two different mutual orientations of Pt versus W units resulting in Pt(2)–W(1), W(1) * separations of 4.77(2), 4.55(2) * and Pt(1)–W(1) of 6.331(8) Å. A centrosymmetric structure reveals groups of two distinct columns: the first is formed by intercalated NO 3− between parallel [Pt(1)(NH 3) 4] 2+ planes and the second consists of [W(CN) 8] 3− interlayered by, parallel to square faces of W-antiprisms, [Pt(2)(NH 3) 4] 2+. The structure is stabilised through a three-dimensional hydrogen bond network via nitrogen atoms of cyanide ligands, hydrogen atoms of NH 3 ligands, water molecules and oxygen atoms of NO 3− counteranions. The vibrational pattern and the range of ν(CN) frequencies attributable to the electronic environment of W(V) and W(IV) are consistent with the ground state Pt(II)↔W(V) charge transfer. 相似文献
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