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In this paper, the generalized travelling solutions of the nonlinear fractional beam equation is investigated by means of the homotopy perturbation method. The fractional derivative is described in the Caputo sense. The reliability and potential of the proposed approach, which is based on joint Fourier-Laplace transforms and the homotopy perturbation method, will be discussed. The solutions can be approximated via an analytical series solution. Moreover, the convergence and stability of the proposed approach for this equation is investigated, and the results reveal that the proposed scheme is very effective and promising. [ABSTRACT FROM AUTHOR]

We developed revolutionary novel and low cost and non-vacuum chemical molecular beam deposition method for fabrication of thin film II-VI solar cells in the atmospheric pressure gas (He, Ar and H2) flow. High quality polycrystalline CdTe films with different compositions (stoichiometric and Cd/Te ⩽1·0 and Cd/Te ⩾1·0) and thickness of 2-3 μm were fabricated on ceramic (SiO2-Al2O3) substrates at a temperature of 600°C. Separate sources of Cd and Te with respective purities of 99·999% were used as precursors. The growth rate was varied in the range of 9-30 Å s-1. The effects of the composition and CdCl2 treatment on the structure, intrinsic point defects and electrical properties of CdTe films were investigated by X-ray diffraction, atomic force microscopy, Raman spectra, photoluminescence and Hall methods. [ABSTRACT FROM AUTHOR]

Abstract: The flame structure of the premixed H2/O2/Ar mixture (13%/14.5%/72.5%vol.) with and without 0.12vol.% of titanium tetraisopropoxide (Ti(OC3H7)4) has been studied experimentally using the flame-sampling molecular beam mass-spectrometry and the microthermocouple techniques. The flame was stabilized on a flat burner at 1atm. The temperature and concentration profiles for Н2, О2, H2O, and Ti(OC3H7)4 have been measured. The mass peak intensity profiles of the titanium-containing species TiO2, HTiO2, TiO, HTiO, Ti, TiH, Ti2O3, TiO3 have been measured as well. The experimental results were analyzed using kinetic modeling and quantum chemical calculations. It was established that hydrolysis of Ti(OC3H7)4 is the dominating primary reaction of its decomposition in the flame. The rate constant of hydrolysis was estimated to be k =2×1012 exp(−6160/T)mol−1 cm3 s−1. The results of quantum chemical computations support this conclusion. On the basis of concentration profiles of the Ti-containing intermediates, the schematic mechanism of the Ti(OC3H7)4 conversion in the flame has been proposed. [Copyright &y& Elsevier]

Abstract: The flame chemistry of tetrahydropyran (THP), a cyclic ether, has been examined using vacuum-ultraviolet (VUV)-photoionization molecular-beam mass spectrometry (PI-MBMS) and flame modeling, motivated by the need to understand and predict the combustion of oxygen-containing, biomass-derived fuels. Species identifications and mole-fraction profiles are presented for a fuel-rich (Φ =1.75), laminar premixed THP–oxygen–argon flame at 2.66kPa (20.0Torr). Flame species with up to six heavy atoms have been detected. A detailed reaction set was developed for THP combustion that captures relevant features of the THP flame quite well, allowing analysis of the dominant kinetic pathways for THP combustion. Necessary rate coefficients and transport parameters were calculated or were estimated by analogies with a recent reaction set [Li et al., Combust. Flame 158 (2011) 2077–2089], and necessary thermochemical properties were computed using the CBS-QB3 method. Our results show that under the low-pressure conditions, THP destruction is dominated by H-abstraction, and the three resulting THP-yl radicals decompose primarily by β-scissions to two- and four-heavy-atom species that are generally destroyed by β-scission, abstraction, or oxidation. [Copyright &y& Elsevier]

Abstract: The overall purpose of the present work is the feasibility study of syngas production from biogas in a microwave plasma discharge. Concentrations of both stable and labile species are presented from molecular beam mass spectrometry (MBMS) measurements in the case of a 50%CH4–16.7%CO2–33.3%H2O mixture. This mixture was chosen as it leads to constant amounts of CO and H2 (respectively 1/3:2/3) in the syngas produced if a complete conversion of the reactants is assumed. Practically, this initial mixture could be produced by any biogas provided that its composition is analyzed and completed to reach the required values. In our study, special attention is paid to the effect of microwave power (600–1600W) and pressure (10–50Torr). A complete modelling initially developed and validated (using several experimental characterization techniques such as Optical Emission Spectroscopy, Microwave Interferometry, Langmuir Probing, MBMS) for diamond deposition purposes is here used to simulate syngas production. This model takes into account the coupled hydrodynamics of the gaseous species and the gas-phase chemistry (including reactions between neutral species and dissociation by electron impact). The surface recombination of radicals at the reactor wall is also modelled. The influence of both power and pressure on syngas production is discussed as well as the transfer of the process to industry. [Copyright &y& Elsevier]

Abstract: An extensive quasiclassical investigation in a quantum spirit of the OH+CO→H+CO2 reaction on the three most popular potential energy surfaces has been performed. Using the standard, the Gaussian and the one dimensional Gaussian binning techniques, product angular and translational energy distributions were calculated and compared with those obtained from the molecular beam experiments. Such a comparison shows that pseudoquantization methods hardly improve the agreement. An analysis of the convergence of the binning methods on the number of reactive trajectories used to calculate the product distributions was also carried out proving that a huge number of trajectories are needed to obtain accurate results in the Gaussian binning case against a significantly lower number in the standard and one dimensional Gaussian binning procedures. Finally, product vibrational distributions of the CO2 molecule were also calculated via pseudoquantization of the vibrational energy of products. Unfortunately, experimental data are not available for comparison. [ABSTRACT FROM AUTHOR]

Abstract: The present study describes the results of two molecular dynamics simulations of 200ns and 300ns in implicit solvent of two anti-HIV peptide T-20 analogues of 42 (T-2042) and 36 residues (T-2036), respectively. Literature studies revealed an absence of NMR studies undertaken, due to poor solubility of the T-2036 peptide in water, in contrast to the T-2042 peptide where its NMR structure is well known. Accordingly this work was undertaken in two stages, the first involved a 200ns MD study of a T-2042 peptide in accordance with the available experimental results, and the second stage involved an assessment of the conformational preferences of a T-2036 peptide from 300ns MD trajectory. The solvent in both simulations was modeled using the Onufriev, Bashford and Case implementation of the Generalized Born procedure. Results obtained from both the trajectories revealed a remarkable difference in their secondary structural features. T-2042 exhibited well-defined α-helical region in the central part of peptide extending towards the C-terminal end, while the corresponding T-2036 peptide adopted turns and loops, in contrast to the reported NMR structure. The results obtained were further validated by two additional MD simulations starting from the helical structures of both the peptides. [ABSTRACT FROM AUTHOR]

Abstract: A methodological study has been undertaken to assess the conformational profile of Neuromedin B (NMB) using classical molecular dynamics simulations (MD) and replica exchange molecular dynamics (REMD) simulations under generalized Born (GB) solvent conditions. Comparison of the results obtained from these simulations suggests that the peptide has a propensity to adopt both β-turns and α-helical conformations regardless of the simulation protocols used. However, the conformations adopted more helical character under REMD conditions and showed good agreement with the NMR supported structure reported in the literature. [ABSTRACT FROM AUTHOR]

Abstract: We discuss an experiment underway at Imperial College London to measure the permanent electric dipole moment (EDM) of the electron using a molecular beam of YbF. We describe the measurement method, which uses a combination of laser and radiofrequency resonance techniques to detect the spin precession of the YbF molecule in a strong electric field. We pay particular attention to the analysis scheme and explore some of the possible systematic e_ects which might mimic the EDM signal. Finally, we describe technical improvements which should increase the sensitivity by more than an order of magnitude over the current experimental limit. [Copyright &y& Elsevier]

Abstract: Flame synthesis of WO3 and WO x (2.9< x <3) nanoparticles is carried out by adding a dilute concentration of WF6 as precursor in a low-pressure H2/O2/Ar premixed flame reactor. The reactor is equipped with molecular-beam sampling and particle mass spectroscopy (PMS) to determine particle composition and sizes as a function of height above burner. Varying the H2/O2 ratio allowed us to tune the stoichiometry of the product. With a H2/O2 ratio of 0.67 white colored stoichiometric WO3 is formed, whereas the H2/O2 ratio >0.8 yields blue colored non-stoichiometric WO x (2.9< x <3) nanoparticles. The size of nanoparticles can be controlled by varying the residence time in the high-temperature zone of the reactor as observed by molecular-beam sampling with subsequent analysis using PMS. Transmission electron microscopy (TEM) images of as-synthesized nanoparticles show that particles are non-agglomerated and have an almost spherical morphology. The X-ray diffraction (XRD) pattern of the as-synthesized material indicates that the powders exhibit poor crystallinity, however, subsequent thermal annealing of the sample in air changes its structure from amorphous to crystalline phase. It is observed that particles with sub-stoichiometric composition (WO x ) show higher conductivity compared to the stoichiometric WO3 sample. [ABSTRACT FROM AUTHOR]

Abstract: An improved chemical kinetic model for the toluene oxidation based on experimental data obtained in a premixed laminar low-pressure flame with vacuum ultraviolet (VUV) photoionization and molecular-beam mass spectrometry (MBMS) techniques has been proposed. The present mechanism consists of 273 species up to chrysene and 1740 reactions. The rate constants of reactions of toluene decomposition, reaction with oxygen, ipso-additions and metatheses with abstraction of phenylic H-atom are updated; new pathways of C4 +C2 species giving benzene and fulvene are added. Based on the experimental observations, combustion intermediates such as fulvenallene, naphthol, methylnaphthalene, acenaphthylene, 2-ethynylnaphthalene, phenanthrene, anthracene, 1-methylphenanthrene, pyrene and chrysene are involved in the present mechanism. The final toluene model leads to an overall satisfactory agreement between the experimentally observed and predicted mole fraction profiles for the major products and most combustion intermediates. The toluene depletion is governed by metathese giving benzyl radicals, ipso-addition forming benzene and metatheses leading to C6H4CH3 radicals. A sensitivity analysis indicates that the unimolecular decomposition via the cleavage of a methyl C–H bond has a strong inhibiting effect, while decomposition via C–C bond breaking, ipso-addition of H-atom to toluene, decomposition of benzyl radicals and reactions related to C6H4CH3 radicals have promoting effect for the consumption of toluene. Moreover, flow rate analysis is performed to illustrate the formation pathways of mono- and polycyclic aromatics. [ABSTRACT FROM AUTHOR]

Abstract: One-dimensional, premixed and laminar toluene–oxygen–argon flames, with equivalence ratios of 0.7 and 1.0 were stabilized at low pressure on a flat flame burner. Mole fraction profiles of 18 chemical species have been measured by gas chromatography and molecular beam mass spectrometry. A kinetic model with a good predictive capability has been developed to compare with experimental data. A comparative reaction rate analysis of predicted flame structures has allowed us to determine main pathways of toluene combustion and their dependence on temperature and equivalence ratio. [ABSTRACT FROM AUTHOR]

Abstract: Molecular beam mass spectrometry (MBMS) and optical diagnostic techniques, two common combustion science diagnostic tools for studying the impact of material on flames, are evaluated as tools for estimating the gas-phase potential of polymer-flame retardant additives. The gas-phase activity of hexabromocyclododecane (HBCD), a widely used commercial flame retardant, was studied and compared via the two combustion diagnostic techniques. MBMS data for HBCD were reviewed and provided identification of gas-phase active species as well as quantitative information on the degree of effectiveness based upon reduction of OH in a premixed CH4/air/N2 flame. In contrast, optical chemiluminescence detection of OH∗ and CH∗ provided a simpler technique for monitoring the gas-phase potential of flame retardants. Studies of CH∗ and OH∗ levels after addition of pyrolyzed products from polystyrene/HBCD blends into a diffusion flame system are compared with MBMS experiments of flames doped with pure HBCD. Comparison of chemiluminescence data with similar data from a small-scale heat release test, the pyrolysis combustion flow calorimeter, indicated that CH∗ and OH∗ activity relate to the heat release rate for flaming combustion. [Copyright &y& Elsevier]

Abstract: A premixed laminar acetylene/oxygen/argon flame with an equivalence ratio of 2.25 was investigated at low pressure (3.3kPa). The flame structure was measured using molecular-beam mass spectrometry (MBMS) and tunable synchrotron vacuum ultraviolet (VUV) photoionization. Combustion intermediates from m/z =15–146, including many radicals and isomeric species, were identified from the ionization threshold measurements of photoionization efficiency spectra; and their mole fraction profiles were evaluated from the measurements of burner scan at the photon energies near ionization thresholds. Besides, the flame temperature profile was recorded by a Pt/Pt–13%Rh thermocouple. In particular, polyynes (C2n H2, n ⩾2) up to C12H2 were observed in this flame and attracted special concerns. Due to the analogous structural features of polyynes and exponential concentration decay with the increasing molecular weight, these intermediates are concluded to be formed from smaller ones via similar formation channels, which can verify the suggestion of previous investigations. Furthermore, another polyynic family with formula of C n H4 (4⩽ n ⩽10) was detected in this flame. Possible formation channels are discussed for the newly observed polyynic C n H4 intermediates in acetylene flames. [Copyright &y& Elsevier]

Abstract: In view of the steady increase in the use of oxygenated fuels, aldehydes play an increasingly important role as intermediates in combustion. The combustion chemistry of propanal was studied in a stoichiometric low-pressure, premixed flat flame. Species mole fraction profiles were measured by electron-ionization molecular beam mass spectrometry (MBMS) for the combustion products, the majority of stable reaction intermediates and several radical species. Based on the mole fraction profiles reactions of the aldehyde fuel are discussed. A number of oxygenated species with a molecular mass exceeding that of the fuel are formed during the early stages of the combustion process. Their presence suggests that addition reactions of small radicals to fuel derived molecules with aldehyde functions play an important role in this flame. [Copyright &y& Elsevier]

Abstract: Structures of diluted ammonia–hydrogen–oxygen–argon flame have been investigated at low pressure by molecular beam mass spectrometry to study the effect of the initial hydrogen content, the equivalence ratio and the working pressure on ammonia combustion. Excluding a slight effect on the NO formation, the initial hydrogen content does not have a significant impact on the composition of the burned gases. Around stoichiometric conditions, a decrease of the equivalence ratio strongly increases the NO formation. Furthermore, at high temperature, the NO formation is favoured as it has been noticed in flames where, due to different heat transfer, the maximum temperature increases with a decrease of pressure. The best agreement of the numerical simulation with the experimental results has been obtained by using Konnov’s mechanism excepted for NH2 and N2O. The impact of the main individual reaction pathways is very similar in all investigated flames. [Copyright &y& Elsevier]

Abstract: The combustion chemistry of morpholine (1-oxa-4-aza-cyclohexane) was investigated under laminar, premixed low-pressure conditions. Morpholine, as a heterocyclic secondary amine with numerous industrial applications, was studied as a model fuel which simultaneously contains oxygen and nitrogen heteroatoms. Stable and radical intermediates and products of the combustion process in a slightly fuel-rich Φ =1.3 (C/O=0.41) flat premixed morpholine–oxygen–argon flame at 40mbar (4kPa) were identified. A detailed fuel destruction scheme is proposed based on combined measurements using two different in situ molecular beam mass spectrometry (MBMS) techniques. The results are discussed with special attention to hydrocarbon, oxygenated and N-containing compounds important in pollutant emission. [Copyright &y& Elsevier]

Abstract: A slightly sooting premixed ethylbenzene flame with an equivalence ratio of 1.90 was investigated at low pressure (4.0kPa) using molecular-beam mass spectrometry (MBMS) and tunable synchrotron vacuum ultraviolet (VUV) photoionization. Basing on the ionization threshold measurements of photoionization efficiency (PIE) spectra, combustion intermediates up to C19H12 were identified, including a number of radicals and isomeric species. Mole fraction profiles of observed flame species were evaluated from the measurements of burner scan at the photon energies near ionization thresholds. Besides, the flame temperature profile was measured by a Pt/Pt–13%Rh thermocouple. From the intermediate identification and mole fraction measurements, the degradation of ethylbenzene, as well as the formation of some interested polycyclic aromatic hydrocarbons (PAHs), was discussed in detail. It is suggested that the formation of most typical PAHs observed in this work can be related to the H-abstraction/C2H2-addition (HACA) mechanism. Furthermore, the high concentration levels of intermediates in this flame is ascribed to the weak C–C bonds in the sidechain of ethylbenzene, which provides a potential explanation of the high sooting tendencies of ethylbenzene and other monocyclic aromatic fuels with complex sidechain structure. This study is anticipated to be constructive for combustion investigations of aromatic fuels, and the discussion is hoped to be helpful for further modeling studies concerning PAHs formation in combustion process. [Copyright &y& Elsevier]

Abstract: The detailed influence of ferrocene in a low-pressure, fuel-rich, laminar, premixed propene/oxygen/argon flat flame was investigated experimentally using molecular beam sampling mass spectrometry (MBMS), laser-induced fluorescence (LIF), and compared to numerical simulations. MBMS was applied to analyze the species profiles of important intermediates in the flames with and without ferrocene doping. The concentration profile of iron atoms was measured with absorption sensitive LIF, which provides absolute number densities without additional calibrations. The flame temperature was obtained by two-line OH LIF measurements. One dimensional numerical simulations of the flames using detailed models from the literature were performed and the modeling results are compared with the experimental measurements. The iron measurements show reasonable agreement with the numerical simulation, while some discrepancies were found at larger heights. The MBMS measurements show a decrease in flame velocity when ferrocene was added, which was not provided by the model. [Copyright &y& Elsevier]

Abstract: A comprehensive experimental study of the premixed benzene/oxygen/argon flame at 4.0kPa with a fuel equivalence ratio (ϕ) of 1.78 has been performed with the tunable synchrotron photoionization and molecular-beam sampling mass spectrometry. Isomers of most observed species in the flame have been unambiguously identified by measurements of the photoionization efficiency spectra. Mole fraction profiles of species up to C16H10 have been measured at the selective photon energies near ionization thresholds, and the flame temperature profile is obtained using Pt/Pt–13%Rh thermocouple. Compared with previous studies on benzene flames by Bittner and Howard, and by Defoeux et al., a number of new species are observed in the present work. These new combustion intermediates should be included in the kinetic models of the growth of polycyclic aromatic hydrocarbons (PAHs) and benzene oxidation. Free radicals detected in the flame include CH3, C2H, C2H3, C2H5, C3H, C3H3, C3H5, C4H, C4H3, C4H5, C4H7, C5H3, C5H5, C5H7, C6H5, C6H5O, C7H7, and C9H7. More significantly, isomers of some PAHs have been identified, which should be of importance in understanding the mechanism of soot formation. [Copyright &y& Elsevier]

Solid source molecular beam epitaxy was applied to create silicon carbide nanoclusters on silicon. The island size distribution can be controlled by appropriate substrate temperature, carbon fluxes and process times. Nevertheless, up to now the earliest stages of the carbon interaction with silicon are not well understood. To have a deeper insight into the early nucleation stages and to investigate the growth laws in such systems the kinetic Monte Carlo computer simulation method was applied. The simulation enabled us to estimate the values of the growth parameters and to obtain the cluster size distribution function and nanocluster concentration in agreement with the experimental obtained data. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Influence of growth conditions in plasma assisted molecular beam epitaxy on quality of GaN layers and GaN/AlGaN heterojunctions is studied. The growth diagram for step-flow growth mode and different nitrogen flux is presented. The low defect density of bulk GaN substrates together with very low impurity background concentrations resulted in high electron mobility for GaN/AlGaN heterojunctions: 109,000 cm2/Vs at 1.5 K, and 2500 cm2/Vs at 295 K. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

InAs/GaAs vertically stacked self-assembled quantum dot (QD) structures with different GaAs spacer layer thicknesses are grown by solid source molecular beam epitaxy (SSMBE) and investigated by transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. An increase in the polarization anisotropy is observed when the spacer layer thickness decreases. For a 10 monolayer (ML) thick inter-dots GaAs spacer, the TEM image shows an increase in the QD size when moving to the upper layer accompanied by the generation of dislocations. Consequently, the corresponding temperature-dependant PL properties are found to exhibit an unusual behaviour. The main PL peak is quenched at a temperature around 190 K giving rise to a broad background correlated with the formation of a miniband in the growth direction due to the strong interlayer coupling. For a thicker GaAs spacer layer (30 ML), multilayer QDs align vertically in stacks with no apparent structural defects. Over the whole temperature range, the excitonic band energies are governed by the Varshni empirical relation using InAs bulk parameters and the PL line width shows a slight monotonic increase. For a thinner GaAs interlayer, the thermal activation energies of the carrier emission out of the quantum dots are found to be considerably small (about 25 meV) due to the existence of defects. By combining these structural and optical results, we can conclude that a thinner GaAs spacer has a poorer quality. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Thin films of La0.7Sr0.3MnO3 with thickness of 300 nm have been grown by computer-controlled laser molecular beam epitaxy on SrTiO3 (001) substrate and were characterized by transmission electron microscopy. It is seen that the films are epitaxially grown on SrTiO3 substrate. Microstructures in the films are clarified by oriented domains of the rhombohedral variant derived from the perovskite structure. Relationships between each domain and the SrTiO3 substrate are discussed. [ABSTRACT FROM AUTHOR]

A molecular-beam apparatus with a spray-jet method was applied for the laser TOF-MS study of naphthalene derivatives, 2-naphthoic acid (2NA), and 1,5-dihydroxynaphthalene (DHN). The results obtained by this method are compared with those obtained by the traditional sample-heating inlet method. The spray-jet method strongly improved the signal-to-noise ratio (S/N), compared to the traditional method. In addition, the intermolecular clusters due to hydrogen-bond formation were observed in case of the DHN system. [ABSTRACT FROM AUTHOR]

The cover picture of this issue of phys. stat. sol. (b), taken from our Editor's Choice [1], is an illustration showing four oriented rhombohedral La0.7Sr0.3MnO3 domains on SrTiO3 substrate. The indexing is on the basis of the hexagonal cell. Thin film of La0.7Sr0.3MnO3 with thickness of 300 nm, which was grown by computer-controlled laser molecular beam epitaxy on SrTiO3 (001) substrate, has been characterized by transmission electron microscopy. Microstructures in the film are clarified in terms of oriented domains of the rhombohedral variant derived from the perovskite structure. Relationships between each domain and SrTiO3 substrate are discussed. [ABSTRACT FROM AUTHOR]