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Purpose: This study analyses the impact of institutional logics on the outcomes of a sporting event's risk process. Design/methodology/approach: The research design is an exploratory case study of the 2017 Road World Cycling Championship using a qualitative approach. By drawing on multiple sources, documents and experiences of six key stakeholders the richness of the qualitative data were utilised to provide a deeper understanding of the impact of institutional logics on the process. Findings: Stakeholders relied on different organisational and professional logics in arguments for certain risk preferences and strategies. Further, the logics behind stakeholder attention varied between stakeholder groups and within a stakeholder group. This led to a tension-filled relationship amongst stakeholders working in the same organisation and between those in different organisations. Finally, new professional practices emerged; however, there were also unintended consequences, such as a large financial deficit, with a significant part of the cost overrun being the risk assessment work. Research limitations/implications: The study includes a case study of a major sporting event that was arranged some years ago. Events are usually organised as temporary projects in collaboration with public sector organisations and must be arranged in accordance with the logics of efficiency as well as meeting the particular needs of citizens. Assuming similar risk planning processes may occur in other contexts is reasonable. Originality/value: The study contributes to knowledge about the impact of logics on the outcome of risk planning and improves scholars' understanding of risk management and the outcomes of planning mega-sporting events. Moreover, insights into these micro-level processes reveal the importance of dealing with the logics that lie beneath stakeholders' perceptions of risk in order to collaborate, achieve common goals, and prevent cost overruns.

Depleted oil reservoirs are considered a viable solution to the global challenge of CO2storage. A key concern is whether the wells can be suitably sealed with cement to hinder the escape of CO2. Under reservoir conditions, CO2is in its supercritical state, and the high pressures and temperatures involved make real-time microscopic observations of cement degradation experimentally challenging. Here, we present an in situ 3D dynamic X-ray micro computed tomography (μ-CT) study of well cement carbonation at realistic reservoir stress, pore-pressure, and temperature conditions. The high-resolution time-lapse 3D images allow monitoring the progress of reaction fronts in Portland cement, including density changes, sample deformation, and mineral precipitation and dissolution. By switching between flow and nonflow conditions of CO2-saturated water through cement, we were able to delineate regimes dominated by calcium carbonate precipitation and dissolution. For the first time, we demonstrate experimentally the impact of the flow history on CO2leakage risk for cement plugging. In-situ μ-CT experiments combined with geochemical modeling provide unique insight into the interactions between CO2and cement, potentially helping in assessing the risks of CO2storage in geological reservoirs.

We demonstrate that the possibility of monitoring relative photoionization cross sections over a large photon energy range allows us to study and disentangle shake processes and intramolecular inelastic scattering effects. In this gas-phase study, relative intensities of the carbon 1s photoelectron lines from chemically inequivalent carbon atoms in the same molecule have been measured as a function of the incident photon energy in the range of 300–6000 eV. We present relative cross sections for the chemically shifted carbon 1s lines in the photoelectron spectra of ethyl trifluoroacetate (the “ESCA” molecule). The results are compared with those of methyl trifluoroacetate and S-ethyl trifluorothioacetate as well as a series of chloro-substituted ethanes and 2-butyne. In the soft X-ray energy range, the cross sections show an extended X-ray absorption fine structure type of wiggles, as was previously observed for a series of chloroethanes. The oscillations are damped in the hard X-ray energy range, but deviations of cross-section ratios from stoichiometry persist, even at high energies. The current findings are supported by theoretical calculations based on a multiple scattering model. The use of soft and tender X-rays provides a more complete picture of the dominant processes accompanying photoionization. Such processes reduce the main photoelectron line intensities by 20–60%. Using both energy ranges enabled us to discern the process of intramolecular inelastic scattering of the outgoing electron, whose significance is otherwise difficult to assess for isolated molecules. This effect relates to the notion of the inelastic mean free path commonly used in photoemission studies of clusters and condensed matter.

It has been hypothesized that a condensed nervous system with a medial ventral nerve cord is an ancestral character of Bilateria. The presence of similar dorsoventral molecular patterns along the nerve cords of vertebrates, flies, and an annelid has been interpreted as support for this scenario. Whether these similarities are generally found across the diversity of bilaterian neuroanatomies is unclear, and thus the evolutionary history of the nervous system is still contentious. Here we study representatives of Xenacoelomorpha, Rotifera, Nemertea, Brachiopoda, and Annelida to assess the conservation of the dorsoventral nerve cord patterning. None of the studied species show a conserved dorsoventral molecular regionalization of their nerve cords, not even the annelid Owenia fusiformis, whose trunk neuroanatomy parallels that of vertebrates and flies. Our findings restrict the use of molecular patterns to explain nervous system evolution, and suggest that the similarities in dorsoventral patterning and trunk neuroanatomies evolved independently in Bilateria.

Natural fragmentation of warheads that detonates causes the casing of the warhead to split into various sized fragments through shear or radial fractures depending on the toughness, density, and grain size of the material. The best known formula for the prediction of the size distribution is the Mott formulae, which is further examined by Grady and Kipp by investigating more carefully the statistical most random way of portioning a given area into a number of entities. We examine the fragmentation behavior of radially expanding steel rings cut from a 25 mm warhead by using an in house smooth particle hydrodynamic (SPH) simulation code called REGULUS. Experimental results were compared with numerical results applying varying particle size and stochastic fracture strain. The numerically obtained number of fragments was consistent with experimental results. Increasing expansion velocity of the rings increases the number of fragments. Statistical variation of the material parameters influences the fragment characteristics, especially for low expansion velocities. A least square regression fit to the cumulative number of fragments by applying a generalized Mott distribution shows that the shape parameter is around 4 for the rings, which is in contrast to the Mott distribution with a shape parameter of ½. For initially polar distributed particles, we see signs of a bimodal cumulative fragment distribution. Adding statistical variation in material parameters of the fracture model causes the velocity numerical solutions to become less sensitive to changes in resolution for Cartesian distributed particles.

A database of 77 adiabatic carbon 1s ionization energies has been prepared, covering linear and cyclic alkanes and alkenes, linear alkynes, and methyl- or fluoro-substituted benzenes. Individual entries are believed to carry uncertainties of less than 30 meV in ionization energies and less than 20 meV for shifts in ionization energies. The database provides an unprecedented opportunity for assessing the accuracy of theoretical schemes for computing inner-shell ionization energies and their corresponding chemical shifts. Chemical shifts in carbon 1s ionization energies have been computed for all molecules in the database using Hartree–Fock, Møller–Plesset (MP) many-body perturbation theory of order 2 and 3 as well as various approximations to full MP4, and the coupled-cluster approximation with single- and double-excitation operators (CCSD) and also including a perturbational estimate of the energy effect of triple-excitation operators (CCSD(T)). Moreover, a wide range of contemporary density functional theory (DFT) methods are also evaluated with respect to computing experimental shifts in C1s ionization energies. Whereas the top ab initiomethods reproduce the observed shifts almost to within the experimental uncertainty, even the best-performing DFT approaches meet with twice the root-mean-squared error and thrice the maximum error compared to CCSD(T). However, a number of different density energy functionals still afford sufficient accuracy to become tools in the analysis of complex C1s photoelectron spectra.

Carbon 1s photoelectron spectra were measured for 1,1-dichloroethene and 1,3-cyclohexadiene adsorbed on Si(111)-7×7 and for gaseous cyclopentene and 1,1-dichloroethene. We explore closely how the molecular spectra of 1,1-dichloroethene and 1,3-cyclohexadiene change upon physisorption and show how gas-phase X-ray photoelectron spectra can be a useful tool for interpretation of spectra of physisorbed molecules. When assigning spectra of adsorbed states, it is frequently assumed that carbon 1s ionization energies (IE) group according to the hybridization state of the carbon atom and, moreover, that sp3-hybridized carbons have lower ionization energies than do sp2-hybridized carbons. These assumptions are explored by reviewing gas-phase spectra where it is possible to assign spectral peaks to individual carbon atoms without ambiguity. In cyclopentene, the carbon 1s ionization energies do group according to hybridization, albeit with the sp3carbons at higher IE than the sp2carbons. In propene, the 1s ionization energy of the central, unsaturated carbon atom groups together with that of the methyl rather than the terminal sp2carbon, almost 0.5 eV higher than the IE of the latter. These findings are backed by a sizable data set, showing unequivocally that the practice of assigning spectra based on the assumption that sp2carbons appear at higher C1s ionization energies than do sp3carbons is unjustified.

Abstract: In this paper we wish to demonstrate to what extent the numerical method regularized smoothed particle hydrodynamics (RSPH) is capable of modelling shocks and shock reflection patterns in a satisfactory manner. The use of SPH based methods to model shock wave problems has been relatively sparse, both due to historical reasons, as the method was originally developed for studies of astrophysical gas dynamics, but also due to the fact that boundary treatment in Lagrangian methods may be a difficult task. The boundary conditions have therefore been given special attention in this paper. Results presented for one quasi-stationary and three non-stationary flow tests reveal a high degree of similarity, when compared to published numerical and experimental data. The difference is found to be below 5, in the case where experimental data was found tabulated. The transition from regular reflection (RR) to Mach reflection (MR) and the opposite transition from MR to RR are studied. The results are found to be in close agreement with the results obtained from various empirical and semi-empirical formulas published in the literature. A convergence test shows a convergence rate slightly steeper than linear, comparable to what is found for other numerical methods when shocks are involved.

Theoretical models of lineshapes in Ar2p photoionization spectra have been calculated for free, neutral argon clusters of different sizes. The lineshape models are fitted to experimental spectra and used to estimate the mean cluster size realized in the experiment. The results indicate that size estimators working from stagnation conditions [R. Karnbach, M. Joppien, J. Stapelfeldt, J. Wörmer and T.Möller, Rev. Sci. Instrum., 1993, 64, 2838] may underestimate the mean cluster size.

A general protocol for theoretical modeling of inner-shell photoelectron spectra of molecular clusters is presented and applied to C1s spectra of oligomers and medium-sized clusters of methanol. The protocol employs molecular dynamics for obtaining cluster geometries and a polarizable force field for computing site-specific chemical shifts in ionization energy and linewidth. Comparisons to spectra computed from first-principle theories are used to establish the accuracy of the proposed force field approach. The model is used to analyze the C1s photoelectron spectrum of medium-sized clusters in terms of surface and bulk contributions. By treating the surface-to-bulk ratio as an adjustable parameter, satisfactory fits are obtained to experimental C1s spectra of a beam of methanol clusters.

Mononuclear Cr(III)–silica models have been studied by quantum chemical methods with respect to catalytic activity toward dehydrogenation of ethane. Both cluster and slab models have been developed and used to explore the conceptual model of mononuclear Cr(III) with three covalent ligands that coordinate through oxygen. The study focuses on a reaction mechanism consisting of three main reaction steps: (1) C—H activation of ethane according to σ‐bond metathesis and accompanied by the formation of O—H and Cr—C bonds, (2) β‐H transfer to chromium with subsequent loss of ethene and (3) regeneration of the chromium site under evolution of H2. An alternative mechanism is also explored, in which C—H activation takes place at a reactive hydridochromium complex. Stationary points pertaining to these reactions have been optimized, and free energy calculations are used to identify the rate‐determining steps. The influence of the local structure of the chromium surface sites is explored by means of a number of idealized surface models and electronic energy profiles for the reactions. Copyright © 2004 John Wiley & Sons, Ltd.

The carbon 1s photoelectron spectra of cyclohexane, cyclohexene, 1,3-cyclohexadiene, and 1,4-cyclohexadiene have been measured. These have been analyzed in terms of a theoretical model of the vibronic structure that includes the effects of the changes in equilibrium geometry that accompany core ionization as well as those of vibronic coupling in the core-ionized molecule. This theoretical approach gives an excellent description of the vibronic structure and makes it possible to identify the contributions of the inequivalent carbon atoms to the spectra. The carbon 1s ionization energies are reported and used in the analysis of photoelectron spectra of adsorbed molecules.

The carbon 1s photoelectron spectra of cyclohexane, cyclohexene, 1,3-cyclohexadiene, and 1,4-cyclohexadiene have been measured. These have been analyzed in terms of a theoretical model of the vibronic structure that includes the effects of the changes in equilibrium geometry that accompany core ionization as well as those of vibronic coupling in the core-ionized molecule. This theoretical approach gives an excellent description of the vibronic structure and makes it possible to identify the contributions of the inequivalent carbon atoms to the spectra. The carbon 1s ionization energies are reported and used in the analysis of photoelectron spectra of adsorbed molecules.

Vibrationally resolved C1s photoelectron spectra of benzene and d₆-benzene have been recorded using monochromated synchrotron radiation at photon energies of 330 eV. The spectrum of normal benzene displays considerable vibrational structure. Particularly noteworthy is the strong excitation of a combined CCH-bending and CC-stretching mode which splits the main peak into two well-defined maxima. In d₆-benzene, the vibrational energy levels are less well separated and the vibrational structure is reduced to strong asymmetry of the main peak and a broad tail extending toward higher ionization energy. The recorded spectra are analyzed using first-principle and curve-fitting procedures. A theoretical model that allows for incomplete localization of the core hole, results in very good fits to the experimental spectra of both benzene and d₆-benzene.

Cluster models are constructed for mono- and dinuclear Cr(II) sites and mononuclear Cr(III) sites on the Cr/SiO2Phillips catalyst and used to compute d–d transition energies and intensities. Mononuclear pseudo-tetrahedral Cr(II) gives rise to two bands of electric-dipole-allowed d–d transitions, at 8,400 and 12,300 cm−1. This doublet is lowered in energy and intensity as the bond angle about chromium, ∠OCrO, opens up. The dinuclear site gives rise to bands at 5,200 and 10,300 cm−1, consistent with calculations for a mononuclear cluster of comparable value for ∠OCrO. A tri-coordinated Cr(III) cluster shows bands of comparable oscillator strengths at energies of 11,000, 16,000, 18,000–20,000 and 33,000 cm−1. The predicted bands correspond well with d–d bands in experimental diffuse reflectance spectra.

The formation and propagation of ion phase-space vortices are observed in a numerical particle-in-cell simulation in two spatial dimensions and with three velocity components. The code allows for an externally applied magnetic field. The electrons are assumed to be isothermally Boltzmann-distributed at all times, implying that Poisson's equation becomes nonlinear for the present problem. Ion phase-space vortices are formed by the nonlinear saturation of the ion-ion two-stream instability, excited by injecting an ion beam at the plasma boundary. We consider the effect of a finite beam diameter and a magnetic field, in particular. A vortex instability is observed, appearing as a transverse modulation, which slowly increases with time and ultimately breaks up the vortex. When many vortices are present at the same time, we find that it is their interaction that eventually leads to a gradual filling-up of the phase-space structures. The ion phase-space vortices have a finite lifetime, which is noticeably shorter than that found in one-dimensional simulations. An externally imposed magnetic field can increase this lifetime considerably. For high injected beam velocities in magnetized plasmas, we observe the excitation of electrostatic ion-cyclotron instabilities, but see no associated formation of ion phase-space vortices. The results are relevant, for instance, for the interpretation of observations by instrumented spacecraft in the Earth's ionosphere and magnetosphere.

Low frequency electrostatic waves are studied in magnetized plasmas with an electron temperature which varies with position in a direction perpendicular to the magnetic field. For wave frequencies below the ion cyclotron frequency, the waves need not follow any definite dispersion relation. Instead a band of phase velocities is allowed, with a range of variation depending on the maximum and minimum values of the electron temperature. Simple model equations are obtained for the general case which can be solved to give the spatial variation of a harmonically time varying potential. A simple analytical model for the phenomenon is presented and the results are supported by numerical simulations carried out in a 2.5-dimensional particle-in-cell numerical simulation. We find that when the electron temperature is striated along B0 and low frequency waves (?«Oci) are excited in this environment, then the intensity of these low frequency waves will be striated in a manner following the electron temperature striations. High frequency ion acoustic waves (?«Oci) will on the other hand have a spatially more uniform intensity distribution.

2,2′-Selenobis(acetic acid), Se(CH2C(O)OH)2, crystallises in the space group P21/cwith the cell dimensions at 253K, a=7.6693(1), b=5.1911(1), c=15.8812(2)Å,β=94.908(1)°, V=629.95(2)Å3,Z=4, Dcalc=2.078Mgm−3, λ(MoKα)=0.71073Å,μ=5.90mm−1.The structure refined to R1=0.0177 for 1727 reflections with Fo>4σ(Fo). In the crystalline state the two carboxylic groups are cisto each other forming dimers with four fairly parallel and linear hydrogen bonds with O⋯O distances ranging from 2.628 to 2.702Å. The two Se–C–C bond angles are distinctly different, 110.2(1) and 116.4(1)°. The selenium atom is surrounded by an intramolecular O (OH) atom, the Se⋯O distance being 3.081Å, and by two intermolecular Se-atoms, both 3.752Å. A re-determination of the crystal structure of S(CH2C(O)OH)2at 253K gave the following parameters: a=5.0572(1), b=17.7896(2), c=6.6726(1)Å,V=600.30(2)Å3,Z=4, Dcalc=1.661Mgm−3,in space group Pnma. The structure was solved as for the Se-compound and previous results by Paul [Acta Cryst. 23 (1967) 491] were confirmed. Theoretical calculations based upon density functional theory suggest that the energy difference between a closed dimer as observed for Se(CH2C(O)OH)2, and a linear chain as observed for S(CH2C(O)OH)2, is small. This indicates that the distinct differences observed between these structures may be due to minor differences in weak intermolecular forces, rather than a preference of the Se atom to make intramolecular non-bonding interactions with hydroxy O atoms.

Cluster models are constructed for mononuclear Cr(II) sites of the Cr/SiO2Phillips catalyst for ethylene polymerization, displaying chromium covalently bound to two oxygen ligands. Based on these models, gradient-corrected density functional theory has been used to compare different routes of initiation and chain propagation with respect to structure, thermodynamical, and kinetical properties. It is shown that, for these sites, propagation mechanisms that involve four-coordinated chromium lead to activation energies that are incompatible with high catalytic activity. In the case of a chromacycloalkane intermediate, the relative rates of β-hydrogen transfer and monomer insertion are in agreement with the observed production of 1-hexene during early stages of polymerization. However, the anchoring site needs to be fairly strained before the activation energies drop significantly below 100 kJ/mol. On the other hand, a monoalkylchromium site supports insertion of ethylene into the Cr–alkyl bond according to the Cossee mechanism, with an activation energy of 56 kJ/mol relative to the ethylene–chromium precursor complex.

This work deals with the synthesis of a new type of compatibilizer suitable for blends or alloys of polypropylene and engineering polymers having aromatic residues or functionality complimentary to hydroxyl. Polypropylene–phenol formaldehyde graft copolymers from thermoplastic phenol formaldehyde (PF) resins and functionalized polypropylene (f-PP) were synthesized by reactive extrusion. The content of PF in the graft copolymer was determined by reaction variables like type and density of functionality on PP, molecular weight of PF, and viscosity ratio of f-PP and PF. The results showed that the viscosity ratio is of primary importance for such reactive processing. Also, type and concentration of the functional groups were important variables. The glycidyl methacrylate functionality resulted in higher conversions than did PP-g-maleic anhydride within the available reaction times. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 347–354, 2000

This work deals with the kinetic and processing aspects of the synthesis of a polypropylene–phenol formaldehyde graft copolymer compatibilizer. This compatibilizer is suitable for blends or alloys of polypropylene and engineering polymers having aromatic residues or functionality complementary to hydroxyl. The compatibilizer is synthesized from thermoplastic phenol formaldehyde (PF) resins and functionalized polypropylene (f-PP) by reactive extrusion. The reaction between maleic anhydride- (PP-g-MAH) and glycidyl methacrylate-functionalized (PP-g-GMA) PP and PF resins followed the predicted models normally used for solvent systems. In a twin-screw extruder, this synthesis was generally best performed in a screw profile offering very intensive mixing and, in particular, with kneading elements located early in the reaction zone. The reaction between PP-g-MAH and PF was enhanced by applying vacuum venting to the system. For the PP-g-GMA and PF reaction, no such effect of a vacuum was observed. The conversion of GMA, with or without catalyst, was generally significantly higher than for the MAH system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 371–378, 2000

A new class of compatibilizers suitable for blends or alloys of polypropylene (PP) and engineering polymers having aromatic residues or functionality complimentary to hydroxyl were evaluated in blends of isotactic PP and poly(butylene terephthalate) (PBT), and poly(phenylene ether) (PPE) PP-based blends with 10–30 wt % PBT or PPE were studied. From response modeling of the PP/PBT and PP/PPE blends, it was evident that the viscosity ratio among the blend component, compatibilizer content, and PBT or PPE content were important for the final blend properties. Impact strength was observed to be the most sensitive response to blend compatibilization. The PP-g-PF compatibilizer was observed to be more efficient in blends of PBT than of PPE. The main reason for that was the availability of reactive end-groups in the case of PBT, making covalent bonding between the compatibilizer and PBT possible. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 361–370, 2000

A new class of compatibilizers suitable for blends or alloys of polypropylene and engineering polymers having aromatic residues or functionality complimentary to hydroxyl were evaluated in blends of isotatctic polypropylene (PP) and polyamide 6 (PA6). The compatibilizer consisted of a PP part with a phenol formaldehyde (PF) polymer grafted onto it. In this study, various combinations of the polymer parameter of each compatibilizer building block were examined. Based on the same loading, the compatibilizer with low molecular weight PP and high content of high molecular weight PF was observed to be the most efficient. A compatibilizer content of up to 7.5% by weight gave significant reduction in the average particle size of the dispersed PA phase. Similarly, corresponding improvements in the mechanical properties were observed as the average particle size was reduced. For some of the blends, more than additive improvement in the mechanical properties were achieved. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 355–360, 2000

Summary The electronic spectrum of O2- is reinvestigated using CASSCF and CI methods. In particular, a previously noted curious flattening of theA2?u curve has been studied in detail. The present analysis disagrees with the previous one where this flattening was found to be a result of an avoided curve crossing between a valence and a Rydberg state of O2-. A simple procedure is suggested to determine whether a wavefunction is of real Rydberg character or if the bound character of the state is just an artefact of the calculation.

Binary mixed monomolecular films of poly(benzyl-methacrylate) and arachidic acid at the water/air interface have been studied with respect to compatibility and stability. The surface pressure — area isotherms indicate compatibility of the two components. However, the miscible state is unstable at high surface pressures. This is demonstrated by the constant pressure relaxation of the mixtures. There is a mechanism of separation and nucleation of the arachidic acid from the film for mixtures with high polymer content at a surface pressure of 30 mN/m. For lower concentrations of polymer in the mixtures and at a surface pressure of 20 mN/m the fatty acid is stabilized by the polymer.

Abstract The PM3(tm) method has been applied to several systems of relevance to catalytic polymerization of olefins, for catalysts containing Ti, Zr or Cr. With some exceptions, PM3(tm) calculations reproduce experimental geometries of stable, closed-shell, precursors well. For stationary points along the path of monomer insertion into a metal-alkyl bond, the comparison is made to structures obtained by optimization using various first-principle methods. Large errors are uncovered for the transient structures, in particular pertaining to metal-ethylene coordination and agostic interactions. The energy profiles for four insertion reactions are computed by gradient-corrected density functional (DFTG) methods, using molecular structures taken from PM3(tm) and first-principle geometry optimizations, respectively. The chromium case is promising, giving values for the barrier to monomer insertion of 11 and 9 kcal/mol based on PM3(tm) and DFTG geometries, respectively. The Ti- and Zr-based systems are predicted to proceed downhill based on PM3(tm) structures, whereas small barriers are found when using first-principle structures. A hybrid PM3(tm)-DFTG procedure is suggested for geometry optimization, which facilitates an accurate estimate of the barrier when applied to one of the zirconium systems.

The adsorption of sodium dodecylsulfate (SDS) and the co-adsorption of SDS and 1-butanol from aqueous electrolyte solutions and from microemulsions containing heptane onto acidic and basic aluminum oxide were measured. The aluminum oxides contain quasi-spherical highly porous particles with an amorphous structure. The measurements were carried out just above the Krafft temperature at 26°C. It is shown that the adsorption capacity of SDS and butanol onto the acidic alumina is slightly higher than that onto the basic. The adsorption of SDS decreases while butanol adsorption increases upon increasing alcohol concentration. The alcohol to surfactant mol ratio on the oxide surface reaches 2.3 for the acidic oxide and 2.1 for the basic oxide in solutions containing 0.8Mbutanol. The result indicates that to a certain degree, SDS becomes gradually replaced by butanol on the alumina surface. In order to describe the surfactant/alcohol exchange on the surface, a simple model is proposed and fitted to the obtained adsorption data. According to this model, the alcohol to surfactant area ratios in the adsorbed patches are 0.48 and 0.71 on the acidic and basic oxide respectively. Addition of heptane does not show any considerable alteration in the adsorption density of the surfactant and alcohol, which indicates that heptane does not solubilize to any appreciable extent in the adsorbed aggregates on the oxide surface.

Adsorption of short chain alcohols in decane solutions onto kaolinite has been investigated by Fourier transform infrared spectroscopy (FTIR) for analysis of the alcohol content. The alcohols were methanol, ethanol, 1-propanol, 2-propanol, and 1-butanol. The isotherms have been mathematically modeled by (i) a basic Langmuir equation, and (ii) a two-term Langmuir equation. In both cases, the equations were modified to take into account the self-association of alcohol molecules in the hydrocarbon solution. The methanol isotherm exhibits two plateaus of differing extent, in addition to a strongly increasing isotherm near the solubility limit. It is suggested that this complex isotherm is to be interpreted in terms of monolayer adsorption and condensation in micropores, followed by condensation at the basal surface at higher concentrations. The results further show adsorption isotherms for ethanol, propanol, and butanol in agreement with monolayer adsorption. The calculated area per molecule for the assumed monolayer increases from about 0.15 nm² for ethanol to 0.34 nm² for butanol. However, 2-propanol gives slightly lower adsorption density than 1-propanol, indicating steric repulsion between the branched chain of the adsorbed molecules. The lower adsorption density of the higher alcohol molecules at the adsorption plateau is possibly caused by steric interactions between the flexible alcohol chains, preventing adsorption onto neighboring sites. Copyright 1995, 1999 Academic Press

Insertion of ethylene into the Ti–methyl bond in TiH2CH+3is chosen as a model reaction for investigating the performance of a range of contemporary quantum chemical models in polymerization studies. Basis set effects are investigated at the self‐consistent‐field level, covering Hartree–Fock, pure DFT, and hybrid DFT. In agreement with findings in part I of this study, the basis set sensitivity of ethylene is shown to introduce a bias in computed energetics, amounting to 2–3 kcal/mol when DZP bases are used to compute the overall heat of monomer insertion. The geometry of stationary points relevant to the insertion reaction is determined using hybrid density functional theory. Based on these structures, the energy profile of the insertion reaction is computed using a range of popular quantum chemical approximations. The methods include Hartree–Fock and Møller–Plesset (MP) perturbation theory up through the fourth order in spin‐restricted, spin‐unrestricted, and spin‐projected formalisms. Furthermore, configuration‐interaction‐based methods are included, of which the top level method is singly and doubly excited coupled clusters with a perturbative estimate of the contribution from triply excited configurations added [CCSD(T)]. The performance of the methods just mentioned, as well as three pure density functional and three hybrid density functional methods, are compared with respect to “best” relative energies, defined through extrapolation of CCSD(T) correlation energies according to the PCI scheme of Siegbahn and coworkers. Even though the MP series show poor convergence, spin‐projected MP2, as well as two pure DFT methods (BPW91, BP86) and PCI‐78 based on the MCPF method, show similar and very good agreement with best relative energies for the insertion reaction. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 947–960, 1998

Hybrid density functional calculations on [Cr(NR)₂C₃H₇(C₂H₄)]+ (R = H, tBu) have revealed a facile reductive elimination reaction involving β-hydrogen transfer from the alkyl chain, suggesting that the active species in ethylene polymerisation with bis(imido)chromium(vi) precursors contains a reduced chromium atom.