Novel layered superstructures in mixed ultralong n-alkanes

Two new types of layered structures were found in binary mixtures of n-alkanes ranging from C122H246 to C294H590. At high temperatures a semicrystalline form is the stable phase, having a regular structure of alternating crystalline and amorphous layers. The two long-chain compounds are mixed in the crystalline layers and the amorphous layers consist of the surplus length of the longer chains. At lower temperatures a reversible transition occurs to a triple layer superlattice structure with a periodicity of up to 50 nm. These two new phases allow the existence of binary solid solutions of chains with a length ratio of up to 1.7 and a chain length difference of 100 CH2 groups.     

The effect of the hydrogen fluoride chain on the aromaticity of C6H6 in the C6H6···(HF)1–4 complexes

The effect of the hydrogen fluoride chain ((HF)_n) on the aromaticity and π character of C–C bonds of C₆H₆ in the C₆H₆···(HF)_n (n = 1–4) complexes were investigated using density functional theory employing RM05 functional. It was found that the binding energy between C₆H₆ and different (HF)_n chains showed a maximum at n = 3 (C₆H₆···(HF)₃). Also, the π–hydrogen interaction (πHI) and the bifurcated fluorine interaction (BFI) increased and decreased the π character of the C–C bond of C₆H₆, respectively. In addition, the change of aromaticity of the C₆H₆ due to the interaction with the HF chains was also studied using three different aspects such as aromatic fluctuation index (FLU), average two centre index (ATI) and proton nuclear magnetic resonance (HNMR) spectrum. The most change in the aromaticity happens when the C₆H₆ interacts with (HF)₃ chain. The variation of aromaticity with the binding energy and the summation of two-body terms were investigated and very good linear correlations were observed.     

On Perpendicular and Tilted Chains in Lamellar Crystals

Chain tilt and surface disorder were investigated in end-deuterated long n-alkane C₁₂D₂₅C₁₉₂H₃₈₄C₁₂HD₂₄ crystallized from solution and in n-alkane C₁₆₂H₃₂₆ crystallized from melt. Small-angle X-ray scattering and infrared spectroscopy were employed. Extended-chain crystals of C₁₂D₂₅C₁₉₂H₃₈₄C₁₂HD₂₄ as-grown from solution have the molecular axis perpendicular to the lamellar surface, but when heated, around 90°C, they start tilting relative to the layer normal. The tilt increases gradually to reach 35° just below the melting point. C₁₆₂H₃₂₆ crystallized from the melt at small supercoolings has chains tilted at 35° at the outset, as found previously for all melt-crystallized long alkanes and polyethylene. However, for the first time in long alkanes, it is found that when molten C₁₆₂H₃₂₆ is supercooled to ΔT≥10 K, crystals with perpendicular chains form. At still larger ΔT, the chains are once-folded, with a mixed population of tilted and perpendicular chain crystals. The use of Davydov splitting of the CH₂ and CD₂ bending vibration of the end-labelled alkane C₁₂D₂₅C₁₉₂H₃₈₄C₁₂HD₂₄ allows independent IR probing of molecular disorder at the deuterated surface and in the hydrogenous crystal interior. The initially small CD₂ splitting and the presence of an additional singlet component indicate a rough surface in as-grown crystals, with considerable longitudinal interchain disorder. It is estimated that about 10% of chains are displaced by up to a dozen C-atoms. The increase in splitting and decrease in absorbance of the singlet, which occur on annealing at progressively higher temperatures, are evidence of steady improvement in translational surface order, occurring simultaneously with increasing chain tilt angle. From the above evidence, it is concluded that the absence of tilt in as-grown crystals is not the result of high surface order, as in the case of shorter odd n-alkanes, but rather of a high frozen-in longitudinal disorder with chain ends or folds protruding out of or sunken beneath the crystal surface. It is also concluded that chain tilt only becomes necessary as the crystal surface becomes translationally more ordered and the crystal–amorphous interface sharpens. The effect of chain tilt on the Davydov splitting is addressed briefly.     

Thermochromic Phase Transition in [NH2(C2H5)2]2CuCl4 Crystals

The absorption spectra of [NH₂(C₂H₅)₂]₂CuCl₄ crystals in the visible spectral region in the vicinity of the thermochromic phase transition at T ₁ = 311 K are investigated. It is shown that in these crystalline compounds the phenomenon of thermochromism is primarily associated with the change of the plane-quadratic geometry of the coordination environment of Cu²⁺ to the tetrahedral form. The influence of ionizing irradiation on the phase-transition temperature and on the thermochromic properties of this crystal is studied.     

Phase transformations in amorphous fullerite C60 under high pressure and high temperature

First phase transformations of amorphous fullerite C₆₀ at high temperatures (up to 1800 K) and high pressures (up to 8 GPa) have been investigated and compared with the previous studies on the crystalline fullerite. The study was conducted using neutron diffraction and Raman spectroscopy. The amorphous fullerite was obtained by ball-milling. We have shown that under thermobaric treatment no crystallization of amorphous fullerite into С₆₀ molecular modification is observed, and it transforms into amorphous-like or crystalline graphite. A kinetic diagram of phase transformation of amorphous fullerite in temperature–pressure coordinates was constructed for the first time. Unlike in crystalline fullerite, no crystalline polymerized phases were formed under thermobaric treatment on amorphous fullerite. We found that amorphous fullerite turned out to be less resistant to thermobaric treatment, and amorphous-like or crystalline graphite were formed at lower temperatures than in crystalline fullerite.     

Structures and stabilities of endo- and exohedral Si20H20 derivatives: X@Si20H20 and XSi20H20, X = H + , H,N, P,C − , and Si −

Geometries, relative energies, and stabilities of endo- and exohedral complexes, X@Si₂₀H₂₀ and XSi₂₀H₂₀, (X = H⁺, H, N, P, C^?, and Si^?) are calculated at B3LYP/6-31G* level. The energy minimum structure of Si₂₀H₂₁ ⁺ shows that the proton cannot be positioned in the Si₂₀H₂₀ centre, but prefers attach to Si₂₀H₂₀ exohedrally with C_2v symmetry. Most investigated I_h endohedral complexes X@Si₂₀H₂₀ (X = H, N, P, C^?, and Si^?) are local minima, except for ²N@Si₂₀H₂₀, which is a high-order saddle point. Inclusions energies of the endohedral complexes are calculated, and it reveals that energy penalties caused by encapsulation are rather small. Exohedral complexes XSi₂₀H₂₀ (X = H, N, P, C^?, and Si^?) have C_2v or C_s local minima, and most of them are more stable than their endohedral isomers with the exception of C_2v ⁴PSi₂₀H₂₀ and ⁴Si^?Si₂₀H₂₀.     

Comparative Plasma Chemical Reaction Studies of CH4/Ar and C2Hm/Ar (m = 2,4,6) Gas Mixtures in a Dielectric Barrier Discharge

Plasma chemical reactions in CH4/Ar and C₂H_m/Ar (m = 2, 4, 6) gas mixtures in a dielectric barrier discharge at medium pressure (300 mbar) have been investigated. From mass spectrometry the production of H₂ and formation of larger hydrocarbons such as C_nH_m with up to n = 12 is inferred. Hydrogen release is most pronounced for CH₄ and C₂H₆ gas mixtures. Fourier Transform InfraRed (FTIR) spectroscopy reveals the formation of substituted alkane (sp³), alkene (sp²), and alkyne (sp) groups from the individual gases which are used in this work. Abundant formation of acetylene occurs from C₂H₄ and to a lesser extent from C₂H₆ and CH₄ precursor gases. The main reaction pathway of acetylene leads to the formation of large molecules via C₄H₂ and, eventually, to nano‐size particles. The experimental results are in reasonable agreement with simulations which predict a pronounced electron temperature and gas pressure dependency. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Computational reconstitution of crystal structures and (p,T) phase diagrams of benzene C6H6 and hexachlorobenzene C6Cl6

Abstract

With a simplified dynamical model for molecular packing analysis, crystal and molecular structures of benzene C₆H₆ and hexachlorobenzene C₆H₆ were investigated. This model includes thermal motion and molecular deformation effects. Several crystalline structures have been found by the calculation. They are compared to experimental structures determined at various temperatures and pressures, by X-ray diffraction or neutron scattering. A schematic (p, T) phase diagram is suggested for each compound.     

A study on detonation-diffraction reflection point distances in H2/O2, C2H2/O2, and C2H4/O2 systems

Recently, Kawasaki and Kasahara (2019) reported that reflection point distance, which is a detonation characteristic length relevant to the diffraction process, is a useful measure; i.e., the critical condition for detonation diffraction can be universally expressed in terms of the diffraction point distance, independent of mixture stability. However, their findings were limited to their experimental conditions only. In this study, we performed high-speed visualization of processes of cylindrical (line-symmetric) detonation diffraction around a 90-degree corner for two series of experiments to obtained reflection point distances, l_r, as a novel characteristic length, and examined critical conditions of reinitiation expressed in terms of the reflection point distance. In the first experimental series, stoichiometric C₂H₂/O₂ mixtures with 50% Ar dilution were employed, and the channel width l_c was varied to 5, 10, 15, and 20 mm to investigate the influences of the boundary condition of the flow field. In the second experimental series, H₂/O₂, C₂H₂/O₂, or C₂H₄/O₂ mixtures with different equivalence ratios were employed to investigate influences of the reaction systems. Our results confirmed that the channel width does not affect the reflection point distance or the critical condition. The critical condition was also independent of fuel species and equivalence ratio, and can be uniquely expressed as l_r / l_c = 4.0 ± 0.6 in terms of the reflection point distance.     

Conformational energies of silacyclohexanes C5H10SiHMe,C5H10SiH(CF3) and C5H10SiCl(SiCl3) from variable temperature Raman spectra

From variable temperature vibrational Raman spectra, the axial/equatorial enthalpy differences for the substituted silacyclohexanes C₅H₁₀SiHMe, C₅H₁₀SiH(CF₃) and C₅H₁₀SiCl(SiCl₃) were determined. The pure liquids and solutions in various solvents were investigated. Preferred conformations are equatorial for methylsilacyclohexane and axial for trifluoromethylsilacyclohexane, consistent with earlier results from nuclear magnetic resonance experiments and ab initio calculations. For C₅H₁₀SiCl(SiCl₃) an enthalpy difference close to zero was found, which is supported by high‐level which is supported by high‐level quantum chemical calculations at the second‐order Møller‐Plesset (MP2) and coupled cluster with single, double, and perturbative triple excitations (CCSD(T)) levels, which employed various basis sets. A novel synthesis for C₅H₁₀SiCl(SiCl₃) was developed using ClMg(CH₂)₅MgCl instead of BrMg(CH₂)₅MgBr as a starting material. The procedure avoids the formation of partially brominated products, facilitating the purification of the compound. ¹H, ¹³C and ²⁹Si nuclear magnetic resonance data are reported. Copyright © 2012 John Wiley & Sons, Ltd.     

Density-dependent magnetic shielding in gas phase 13C N.M.R.

Density-dependent ¹³C nuclear magnetic shielding has been found for each of the pure gases CH₄, C₂H₆, C₂H₄, CO and CO₂, and for several binary mixtures of gases. For methane gas the density dependence is greater at higher temperatures in contrast to expectation and the observed temperature dependence of the shielding at zero density is attributable to nuclear motion. ¹³C magnetic shielding is considerably higher in the gas phase than in the liquid phase and the difference varies for chemically non-equivalent ¹³C nuclei by amounts which are well above the level of experimental error.     

Hidden chemistry in phenoxyl radical (C6H5O•) coupling reaction mechanism revealed

A novel hidden reaction of the phenoxyl radical (C₆H₅O^?) with a specific daughter is found to significantly alter its hitherto accepted coupling reactions' scheme. Transient characterizations and mechanistic evaluations in highly acidic to strongly alkaline aqueous medium reveal this concurrent reaction competing favorably in nanosecond–microsecond time‐scale with the five distinct C₆H₅O^? + C₆H₅O^? reactions, which produce various phenolic end‐products as reported earlier (M. Ye and R. H. Schuler, J. Phys. Chem. 1989, 93, 1898). Presently, only the symmetric 4,4′‐dioxo transient precursor, O?C₆H₅? H₅C₆?O that leads to the stable 4,4′‐biphenol product, gets partially oxidized by a fraction of remaining C₆H₅O^?. The resulting secondary transient ^?C₁₂H₉O₂ radical is generated at diffusion‐controlled rate, k > 5.0 × 10⁹ M^?1 s^?1, and follows an independent chemistry. Consequently, when the previously reported five coupled end product distribution ratios were appropriately updated, the respective fractional values revealed a closer match for the symmetric 2,2′‐ and 4,4′‐biphenols with their suggested coupling reaction branching probabilities based on the atomic spin‐density distributions in the C₆H₅O^? radical (P. Neta, R. W. Fessenden, J. Phys. Chem., 1974, 78, 523). Results also suggest that in the remaining fraction, differential solvation in aqueous medium of various orientation‐related encounter complexes (C₆H₅O…C₆H₅O) formed during coupling favors rearrangement only toward 2,4′‐biphenolic product, at the cost of 2‐ and 4‐phenoxyphenolic species. Copyright © 2009 John Wiley & Sons, Ltd.     

Hartree–Fock and density functional theory study of remote substituent effects on heterolytic Fe―C bond energies of p‐G‐C6H4CH2Fe(CO)2(η5‐C5H5) and p‐G‐C6H4(H)(CN)CFe(CO)2(η5‐C5H5)

Knowledge of the strength of the metal–ligand bond breaking and formation is fundamental for an understanding of the thermodynamics underlying many important stoichiometric and catalytic organometallic reactions. Quantum chemical calculations at different levels of theory have been used to investigate heterolytic Fe―C bond energies of para‐substituted benzyldicarbonyl(η⁵‐cyclopentadienyl)iron, p‐G‐C₆H₄CH₂Fp [1, G = NO₂, CN, COMe, CO₂Me, CF₃, Br, Cl, F, H, Me, MeO, NMe₂; Fp = (η⁵‐C₅H₅)(CO)₂Fe], and para‐substituted α‐cyanobenzyldicarbonyl(η⁵‐cyclopentadienyl)iron, p‐G‐PANFp [2, PAN = C₆H₄CH(CN)]. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and more accurate predictions in the study of ΔH_het(Fe―C)'s. The good linear correlations [r = 0.98 (g, 1a), 0.99 (g, 2b)] between the substituent effects of heterolytic Fe―C bond energies [ΔΔH_het(Fe―C)'s] of series 1 and 2 and the differences of acidic dissociation constants (ΔpK_a) of C―H bonds of p‐G‐C₆H₄CH₃ and p‐G‐C₆H₄CH₂CN imply that the governing structural factors for these bond scissions are similar. And the excellent linear correlations [r = ?1.00 (g, 1c), ?0.99 (g, 2d)] between ΔΔH_het(Fe―C)'s and the substituent σ_p^? constants show that these correlations are in accordance with Hammett linear free energy relationships. The polar effects of these substituents and the basis set effects influence the accuracy of ΔH_het(Fe―C)'s. ΔΔH_het(Fe―C)'s(1, 2) follow the Capto‐dative Principle. The detailed knowledge of the factors that determine the Fp―C bond strengths would greatly aid in understanding reactivity patterns in many processes. Copyright © 2011 John Wiley & Sons, Ltd.     

Absolute line wavenumbers in the near infrared: 12C2H2 and 12C16O2

40 absolute line wavenumbers in the 3v ₃ band of ¹²C¹⁶O₂ between 6927 cm^?1 and 6989 cm^?1 and 626 absolute line wavenumbers in the near infrared absorption spectrum of ¹²C₂H₂ between 7060 cm^?1 and 9900 cm^?1 have been measured using high resolution Fourier transform spectroscopy. The calibration of the CO₂ line wavenumbers relied on heterodyne frequencies available in the v ₁ + v ₃ band of ¹²C₂H₂ near 6556 cm^?1. The absolute uncertainty of the calibrated CO₂ line wavenumbers is estimated to 0.000 08 cm^?1. The acetylene spectra were calibrated using heterodyne frequencies available in the 2—0 band of ¹²C¹⁶O and the line wavenumbers obtained in the 3v ₃ band of ¹²C¹⁶O₂. The absolute uncertainty of the calibrated acetylene line wavenumbers is estimated to range from 0.0003 cm^?1 to 0.006 cm^?1 for strong to very weak isolated lines. Comparison with absolute line wavenumbers obtained independently at JPL in the 3v ₃ band of ¹²C₂H₂ near 9649 cm^?1, calibrated using absolute wavenumbers available in the 2—0 and 3—0 (near 6350 cm^?1) bands of ¹²C¹⁶O, shows very good agreement. Also, the vibration—rotation constants for the observed upper vibrational states of ¹²C₂H₂ were determined, but without accounting for the perturbations affecting these states.     

Phase Transitions in a Mixture of Amorphous C<Subscript>60</Subscript> and C<Subscript>70</Subscript> Fullerene Phases at High Temperatures and Pressures

Phase transitions in two types of amorphous fullerene phases (C₆₀–C₇₀ (50/50) mixtures and an amorpous C₇₀ fullerene phase) are studied via neutron diffraction at pressures of 2–8 GPa and temperatures of 200–1100°C. Fullerenes are amorphized by grinding in a ball mill and sintered under quasi-hydrostatic pressure in a toroidal-type chamber. Diffraction studies are performed ex situ. It is shown that the amorphous phase of fullerenes retains its structure at temperatures of 200–500°C, and amorphous graphite is formed at 800–1100°C with a subsequent transition to crystalline graphite. This process is slow in a mixture of fullerenes, compared to C₇₀ fullerene. According to neutron diffraction data, the amorphous graphite formed from amorphous fullerene phases has anisotropy that is much weaker in a fullerene mixture.     

Hartree–Fock and density functional theory study of remote substituent effects on heterolytic Fe–N bond energies of p‐G‐C6H4NHFe(CO)2(η5‐C5H5) and p‐G‐C6H4N(COMe)Fe(CO)2(η5‐C5H5)

The nature and strength of metal–ligand bonds in organotransition‐metal complexes are crucial to the understanding of organometallic reactions and catalysis. Quantum chemical calculations at different levels of theory have been used to investigate heterolytic Fe–N bond energies of para‐substituted anilinyldicarbonyl(η⁵‐cyclopentadienyl)iron [p‐G‐C₆H₄NH(η⁵‐C₅H₅)Fe(CO)₂, abbreviated as p‐G‐C₆H₄NHFp (1), where G = NO₂, CN, COMe, CO₂Me, CF₃, Br, Cl, F, H, Me, MeO, and NMe₂] and para‐substituted α‐acetylanilinyldicarbonyl(η⁵‐cyclopentadienyl)iron [p‐G‐C₆H₄N(COMe)(η⁵‐C₅H₅)Fe(CO)₂, abbreviated as p‐G‐C₆H₄N(COMe)Fp (2)] complexes. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and more accurate predictions in the study of ΔH_het(Fe–N)'s. The linear correlations [r = 0.98 (g, 1a), 0.93 (g, 2b)] between the substituent effects of heterolytic Fe–N bond energies [ΔΔH_het(Fe–N)'s] of series 1 and 2 and the differences of acidic dissociation constants (ΔpK_a) of N–H bonds of p‐G‐C₆H₄NH₂ and p‐G‐C₆H₄NH(COMe) imply that the governing structural factors for these bond scissions are similar. And the linear correlations [r = ?0.99 (g, 1c), ?0.92 (g, 2d)] between ΔΔH_het(Fe–N)'s and the substituent σ_p^? constants show that these correlations are in accordance with Hammett linear free energy relationships. The polar effects of these substituents and the basis set effects influence the accuracy of ΔH_het(Fe–N)'s. ΔΔH_het(Fe–N)'s(1, 2) follow the captodative principle. ME_{α‐COMe, para‐G}s include the influences of the whole molecules. The correlation of ME_{α‐COMe, para‐G}s with σ_p^? is excellent. ME_{α‐COMe, para‐G}s rather than ΔΔH_het(Fe–N)'s in series 2 are more suitable indexes for the overall substituent effects on ΔH_het(Fe–N)'s(2). Insight from this work may help the design of more effective catalytic processes. Copyright © 2012 John Wiley & Sons, Ltd.     

Comparisons of some molecular properties calculated with basis sets of Slater-type orbitals and floating spherical gaussian orbitals for BH3, BH4 -, B2H6, B4H4, C2H2, C2H4, C2H6, CH4, and C3H4

Some one-electron molecular properties are calculated for BH₃, BH₄ ^-, B₂H₆, B₄H₄, CH₄, C₂H₂, C₂H₄, C₂H₆, and C₃H₄. The wave functions used are constructed from minimal basis sets of STO's and FSGO's. The results obtained from the latter wave functions show that the good agreement with the STO values of the molecular energy is not always maintained with one-electron properties.     

The integrated number of vibrational states in acetylene (12C2H2, 13C2H2, 12C2D2)

A calculated exhaustive set of vibrational state energies in ¹²C₂H₂, ¹³C₂H₂ and ¹²C₂D₂ has been used to analyse the evolution of the integrated number of states with increasing vibrational energy N(E) up to 15000 cm^?1, 12000cm^?1 and 10000 cm^?1 in each isotopomer, respectively. The regular contribution to N(E) was modelled analytically and numerical parameters were fitted. The other expected contribution to N(E), which is of oscillatory nature, was quantified and is discussed using energyand time-dependent theories. Related periods of oscillation and temporal recurrences are interpreted consistently in terms of the constant of the motion N_r = 5v₂ + 3v₂ + 5v₃ + v₄ + v₅ and of an average vibrational quantum. More pragmatically, the vibrational dynamics appear to be dominated by the bending vibrations, i.e., by the slowest oscillators.     

Oxygen as promoter or poison in the catalytic dissociation of H2, C2H4, C2H2, and NH3 on Palladium

The dissociation rates of H₂, C₂H₄, C₂H₄, and NH₃ have been studied on oxygen covered Pd surfaces by measuring the water desorption rates during exposure to each of the molecules. These results are correlated with the hydrogen response of a Pd-MOS structure. The measurements show a trend (at 473 K) where oxygen blocks H₂ dissociation, blocks C₂H₄ dissociation only above a certain oxygen coverage, has no influence on C₂H₂ dissociation, and promotes NH₃ dissociation.     

Hartree–Fock and density functional theory study of remote substituent effects on gas‐phase heterolytic Fe–O and Fe–S bond energies of p‐G‐C6H4OFe(CO)2(η5‐C5H5) and p‐G‐C6H4SFe(CO)2(η5‐C5H5)

The knowledge of accurate bond strengths is a fundamental basis for a proper analysis of chemical reaction mechanisms. Quantum chemical calculations at different levels of theory have been used to investigate heterolytic Fe–O and Fe–S bond energies of para‐substituted phenoxydicarbonyl(η⁵‐cyclopentadienyl) iron [p‐G‐C₆H₄O(η⁵‐C₅H₅)Fe(CO)₂, abbreviated as p‐G‐C₆H₄OFp ( 1 ), where G = NO₂, CN, COMe, CO₂Me, CF₃, Br, Cl, F, H, Me, MeO, and NMe₂] and para‐substituted benzenethiolatodicarbonyl(η⁵‐cyclopentadienyl) iron [p‐G‐C₆H₄S(η⁵‐C₅H₅)Fe(CO)₂, abbreviated as p‐G‐C₆H₄SFp ( 2 )] complexes. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and more accurate predictions in the study of ΔH_het(Fe–O)'s and ΔH_het(Fe–S)'s. The excellent linear free‐energy relations [r = 0.99 (g, 1a), 1.00 (g, 2b)] among the ΔΔH_het (Fe–O)'s and Δpk_a's of O–H bonds of p‐G‐C₆H₄OH or ΔΔH_het(Fe‐S)'s and Δpk_a's of S–H bonds of p‐G‐C₆H₄SH imply that the governing structural factors for these bond scissions are similar. And the linear correlations [r = ?0.99 (g, 1g), ?0.98 (g, 2h)] among the ΔΔH_het (Fe‐O)'s or ΔΔH_het(Fe‐S)'s and the substituent σ_p^? constants show that these correlations are in accordance with Hammett linear free‐energy relationships. The polar effects of these substituents and the basis set effects influence the accuracy of ΔH_het(Fe–O)'s or ΔH_het(Fe–S)'s. ΔΔH_het(Fe–O)'s(g) ( 1 ) and ΔΔH_het(Fe–S)'s(g)( 2 ) follow the Capto‐dative principle. The substituent effects on the Fe–O bonds are much stronger than those on the less polar Fe–S bonds. Insight from this work may help the design of more effective catalytic processes. Copyright © 2013 John Wiley & Sons, Ltd.