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Functionalization of vertically aligned multiwalled carbon nanotube carpets was performed via exposure to CF4 or Ar:F2 RF plasmas. Rapid fluorination was observed via X-ray photoelectron spectroscopy (XPS) with surface fluorine co...
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Functionalization of vertically aligned multiwalled carbon nanotube carpets was performed via exposure to CF4 or Ar:F2 RF plasmas. Rapid fluorination was observed via X-ray photoelectron spectroscopy (XPS) with surface fluorine concentration, bonding type, and patterning dependent on gas mixture and exposure time. Surface properties of the v-MWCNTs forests have been changed by the introduction of fluorine-containing groups, as demonstrated via surface wettability studies, while scanning electron microscopy shows that overall nanotube alignment and separation is conserved. Scanning X-ray photoelectron spectromicroscopy (SPEM) shows that the plasma treatment results in selective functionalization of the surface tips of the nanotubes. This opens the way to nanotube carpet structures with activated surfaces, which maintain the desirable conductive properties of the pristine nanotubes near to the substrate.
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When dipolar gases are condensed at sufficiently low temperature onto a solid surface, they form films that may spontaneously exhibit electric fields in excess of 10~8 V/m. This effect, called the 'spontelectric effect', was recen...
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When dipolar gases are condensed at sufficiently low temperature onto a solid surface, they form films that may spontaneously exhibit electric fields in excess of 10~8 V/m. This effect, called the 'spontelectric effect', was recently revealed using an instrument designed to measure scattering and capture of low energy electrons by molecular films. In this review it is described how this discovery was made and the properties of materials that display the spontelectric effect, so-called 'spontelectrics', are set out. A discussion is included of properties that differentiate spontelectrics from ferroelectrics and other species in which spontaneous polarisation may be found. Spontelectric films may be composed of a number of quite mundane dipolar molecules that involve such diverse dipolar species as propane, nitrous oxide or methyl formate. Experimental results are presented for spontelectrics illustrating that the spontelectric field generally decreases monotonically with increasing deposition temperature, with the exception of methyl formate that shows an increase beyond a critical range of deposition temperature. Films of spontelectric material show a Curie temperature above which the spontelectric effect disappears. Heterolayers may also be laid down creating potential wells on the nanoscale. A model is put forward based upon competition between dipole alignment and thermal disorder, which is successful in reproducing the variation of the degree of dipole alignment and the spontelectric field with deposition temperature, including the behaviour of methyl formate. This model and associated data lead to the conclusion that the spontelectric effect is new in solid-state physics and that spontelectrics represent a new class of materials.
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Computational quantum chemistry can make valuable contributions to modelling and improving free radical polymerisation. At a microscopic level, it can assist in establishing reaction mechanisms and structure-reactivity trends; at ...
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Computational quantum chemistry can make valuable contributions to modelling and improving free radical polymerisation. At a microscopic level, it can assist in establishing reaction mechanisms and structure-reactivity trends; at a macroscopic level it can be used in the design and parameterisation of accurate kinetic models for process optimisation and control. This review outlines and critically evaluates various methodological approaches that have been employed in first principles prediction of rate coefficients in free radical polymerisation, examining in turn the choice of chemical model, electronic structure method, solvation modelling and the coupled issues of partition function evaluation and conformational analysis. It is shown that accurate and reliable predictions are possible but only if necessary precautions are taken into account. The practical value of accurate computational modelling of radical polymerisation kinetics is then illustrated through three representative case studies from the literature in which theory has been used to develop accurate kinetic models: free radical copolymerisation kinetics; defect structure formation in radical suspension polymerisation of vinyl chloride; and reversible addition fragmentation chain transfer polymerisation.
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A large number of molecules referred to here as M, several of which are extracted from plants, belong to different chemical classes and exhibit chemoprotective activity against carcinogenesis and inflammation in rodents and in vit...
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A large number of molecules referred to here as M, several of which are extracted from plants, belong to different chemical classes and exhibit chemoprotective activity against carcinogenesis and inflammation in rodents and in vitro cell culture. The aim of this article is to review and analyse our previous investigations on linear correlations observed between physicochemical parameters of the tested molecules M and their biological efficacies measured in vivo and/or in vitro. The principal physicochemical parameters studied characterise the energy required to oxidise M into M~(?+), E(M~(?+)/M), namely its first vertical ionisation potential, and the energy liberated by the addition of an electron to M, i.e. its vertical electron affinity. These physicochemical properties were determined experimentally using diverse techniques and theoretically using mainly semiempirical (AM1) and density functional theory (DFT) quantum mechanical methods.
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Excess molar volumes V ~E for 40 mixtures of heptane with a liquid alkane and apparent molar volumes in heptane for eight solid alkanes have been obtained at 298.15 K. They include five linear, 30 branched-chain, and 13 cyclic alk...
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Excess molar volumes V ~E for 40 mixtures of heptane with a liquid alkane and apparent molar volumes in heptane for eight solid alkanes have been obtained at 298.15 K. They include five linear, 30 branched-chain, and 13 cyclic alkanes. Almost all systems exhibit negative V ~E values. For mixtures with open chain alkanes, V ~E increases from C5 to C7 and then decreases. A similar trend is shown by mixtures with cycloalkanes. V ~E values are compared with known H ~E data for mixtures with heptane and tetrachloromethane. Signs and trends of V ~E and H ~E are correlated with the free volume and interactional terms of the Flory theory. The partial molar volumes at infinite dilution in heptane, V, have also been obtained and discussed together with literature data on other hydrocarbons and polar compounds. The calculated contributions to V by CH _3, CH_2, CH and C groups are compared with previously determined contributions of polar groups. The lower contributions of the latter groups are explained with the volume contraction caused by dipole-induced dipole interaction. The volume effects associated with branching and cyclization have been evaluated and compared with the corresponding effects on solvation enthalpy. The branching effect, in the order of magnitude of few cm ~3·mol~(-1), and the larger negative values of cyclization volumes, down to -24 cm~3·mol~(-1), are discussed in terms of packing and solute-solvent interactions, in analogy to polar organic solutes either in heptane and tetrachloromethane. A negative cyclization effect is also exhibited by the solvation enthalpies.
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A detailed chemical kinetic mechanism has been developed to describe the oxidation of small hydrocarbon and oxygenated hydrocarbon species. The reactivity of these small fuels and intermediates is of critical importance in underst...
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A detailed chemical kinetic mechanism has been developed to describe the oxidation of small hydrocarbon and oxygenated hydrocarbon species. The reactivity of these small fuels and intermediates is of critical importance in understanding and accurately describing the combustion characteristics, such as ignition delay time, flame speed, and emissions of practical fuels. The chosen rate expressions have been assembled through critical evaluation of the literature, with minimum optimization performed. The mechanism has been validated over a wide range of initial conditions and experimental devices, including flow reactor, shock tube, jet-stirred reactor, and flame studies. The current mechanism contains accurate kinetic descriptions for saturated and unsaturated hydrocarbons, namely methane, ethane, ethylene, and acetylene, and oxygenated species; formaldehyde, methanol, acetaldehyde, and ethanol.
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The development of continuous predictive correlations for the temperature dependence of the ideal gas heat capacity for hydrocarbons and substituted hydrocarbons valid over a wide range of elemental compositions (CHNOS), molecular...
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The development of continuous predictive correlations for the temperature dependence of the ideal gas heat capacity for hydrocarbons and substituted hydrocarbons valid over a wide range of elemental compositions (CHNOS), molecular structures, and temperatures (298.15-1500. K) is reported. The correlations are functions of temperature, elemental composition, and 10 (naphthenic hydrocarbons) or 12 (aromatic and aliphatic hydrocarbons) universal coefficients. There are no compound specific coefficients. The variables are absolute temperature and a similarity variable, which possesses a value proportional to the number of atoms in a molecule, irrespective of their nature, divided by molecular mass. Different data sets obtained from the NIST TRC Ideal Gas Database 88 were used to evaluate parameters, and to test the predictive nature of the correlations. Detailed comparisons between predicted ideal gas heat capacities (cpg0) obtained in this work and values obtained using four Lee-Kesler correlations, and the Harrison-Seaton correlation are presented. The present correlations are shown to be preferred over these other options on the basis of accuracy and range of application for general-purpose calculations, unless the fluid assignment (naphthenic vs. aromatic/aliphatic) is unknown and cpg0 values are only required at set temperatures available for the Harrison-Seaton correlation. In this latter case, the Harrison-Seaton correlation is preferred. For large molecules, the universal correlations presented in this work approach the accuracy of the benchmark Benson method. The universal correlations are well suited for the determination of ideal gas heat capacities of large and complex molecules or mixtures, where more precise structure-property group contribution correlations are difficult to apply or are inapplicable because groups present are not defined in the correlations or are unknown.
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The past few decades have witnessed the development of intricate strategies and management in pharmaceutical research to combat various diseases and provide physical comfort to the living beings. Efforts are on to design efficient...
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The past few decades have witnessed the development of intricate strategies and management in pharmaceutical research to combat various diseases and provide physical comfort to the living beings. Efforts are on to design efficient drug delivery systems, achieve desirable therapeutic objectives and to minimise drug-induced adverse side effects. The role of the self-assembled micro or nanostructures as vehicles in drug delivery has often remained at the focus since they serve as the drug carriers for controlled and sustained release of drugs. Efficacy of drug is also an important aspect to consider and attempts are being made to enhance it exploiting indigenous strategies. The foundation of these researches rests on understanding the binding of various molecular drugs with the biomacromolecules through specific or non-specific interactions. Dyes and biomimetic microheterogeneous environments are often exploited as models of drugs and biosystems, respectively, for understanding the binding processes since they play a crucial role in the function of the biological systems. Focusing on this aspect, in this review, we have discussed on the equilibrium and dynamic aspects of binding of various dyes with biomacromolecules and biomimetic model systems.
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In this study, a quantitative structure-liquid thermal conductivity relationship was developed for pure mostly organic chemical compounds. An extensive data set including more than 19,000 evaluated liquid thermal conductivity data...
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In this study, a quantitative structure-liquid thermal conductivity relationship was developed for pure mostly organic chemical compounds. An extensive data set including more than 19,000 evaluated liquid thermal conductivity data for 1635 pure mostly organic chemical compounds at various temperatures and at atmospheric pressure below the normal boiling point and at saturated pressure above the normal boiling point temperature was provided from DIPPR 801 database to develop, validate and assess the predictive capabilities of the obtained correlation. Parameters of the model comprise 20 molecular descriptors including temperature. The obtained model shows a good agreement with DIPPR 801 data. The model shows the same values of the average absolute relative deviation and root mean square error of 7.4% and 0.01 for the training set (80% of the data), the validation set (10% of the data), and the test set (10% of the data). In terms of wide range of applicability, the model shows reasonable accuracy.
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Electronic energy transfer in photosynthesis occurs over a range of time scales and under a variety of intermolecular coupling conditions. Recent work has shown that electronic coupling between chromophores can lead to coherent os...
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Electronic energy transfer in photosynthesis occurs over a range of time scales and under a variety of intermolecular coupling conditions. Recent work has shown that electronic coupling between chromophores can lead to coherent oscillations in two-dimensional electronic spectroscopy measurements of pigment-protein complexes measured with femtosecond laser pulses. A persistent issue in the field is to reconcile the results of measurements performed using femtosecond laser pulses with physiological illumination conditions. Noisy-light spectroscopy can begin to address this question. In this work we present the theoretical analysis of incoherent two-dimensional electronic spectroscopy, I~((4)) 2D ES. Simulations reveal diagonal peaks, cross peaks, and coherent oscillations similar to those observed in femtosecond two-dimensional electronic spectroscopy experiments. The results also expose fundamental differences between the femtosecond-pulse and noisy-light techniques; the differences lead to new challenges and new opportunities.
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