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Dimethyl fumarate (DMF) is an immunomodulatory treatment for multiple sclerosis (MS) that can cross the blood–brain barrier, presenting neuroprotective potential. Its mechanism of action is not fully understood, and there is a need to characterize whether DMF or its bioactive metabolite monomethyl fumarate (MMF) exerts neuroprotective properties. Moreover, the combination of adjuvant agents such as cannabidiol (CBD) could be relevant to enhance neuroprotection. The aim of this study was to compare the neuroprotective and immunomodulatory effects of DMF, MMF, and CBD in neurons and microglia in vitro. We found that DMF and CBD, but not MMF, activated the Nrf2 antioxidant pathway in neurons. Similarly, only DMF and CBD, but not MMF, prevented the LPS-induced activation of the inflammatory pathway NF-kB in microglia. Additionally, the three drugs inhibited the production of nitric oxide in microglia and protected neurons against apoptosis. Transcriptomically, DMF modulated a greater number of inflammatory and Nrf2-related genes compared to MMF and CBD in both neurons and microglia. Our results show that DMF and MMF, despite being structurally related, present differences in their mechanisms of action that could be relevant for the achievement of neuroprotection in MS patients. Additionally, CBD shows potential as a neuroprotective agent. [ABSTRACT FROM AUTHOR]

The aim of this paper is to address the colonisation of the Pontus in relation to the Amazon myths. An attempt will be made to clarify the difficulties in identifying both the initial contacts between the Greeks and the ancient steppe nomad peoples in that region and the origin of the Amazon myths on the basis of the apparently more egalitarian lifestyle of those societies². Similarly, the intention is to offer an explanation for the presence of iconographic pieces of an Amazon character in that liminal space. The Amazon kingdom, regardless of whether it has been located preferably in the southern Pontus or less frequently in its northern or eastern reaches, was undoubtedly connected with the Black Sea. Even though those myths are rooted in a time long before the period in which the region was colonised by the Greeks, they formed part of it, as occurred with many other accounts dealing with the Argonauts, Medea and so forth, with the mission of exploring those distant lands, bringing them closer to the Greek world and facilitating their control, as well as converting them into essential elements for identifying the 'other' and, by extension, Hellenic culture itself. [ABSTRACT FROM AUTHOR]

Fingolimod is an immunomodulatory sphingosine-1-phosphate (S1P) analogue approved for the treatment of relapsing-remitting multiple sclerosis (RRMS). The identification of biomarkers of clinical responses to fingolimod is a major necessity in MS to identify optimal responders and avoid the risk of disease progression in non-responders. With this aim, we used RNA sequencing to study the transcriptomic changes induced by fingolimod in peripheral blood mononuclear cells of MS-treated patients and their association with clinical response. Samples were obtained from 10 RRMS patients (five responders and five non-responders) at baseline and at 12 months of fingolimod therapy. Fingolimod exerted a vast impact at the transcriptional level, identifying 7155 differentially expressed genes (DEGs) compared to baseline that affected the regulation of numerous signaling pathways. These DEGs were predominantly immune related, including genes associated with S1P metabolism, cytokines, lymphocyte trafficking, master transcription factors of lymphocyte functions and the NF-kB pathway. Responder and non-responder patients exhibited a differential transcriptomic regulation during treatment, with responders presenting a higher number of DEGs (6405) compared to non-responders (2653). The S1P, NF-kB and TCR signaling pathways were differentially modulated in responder and non-responder patients. These transcriptomic differences offer the potential of being exploited as biomarkers of a clinical response to fingolimod. [ABSTRACT FROM AUTHOR]

There is currently a great deal of research on mindfulness in the field of education at different levels. In higher education, most of these studies have been approached from a positivist view of the phenomenon, and have focused on assessing the benefits of mindfulness on the health and well-being of students, as well as on their academic performance. The aim of this study was to explore the experiences of three university teachers who focus their educational work as a conscious experience, through the analysis of their life stories. The technique used was the semi-structured interview. Data analysis was performed in two successive phases. The first consisted of a category analysis of the content of the interviews, and the second on reducing the data according to the objectives of the research, showing three different approaches to mindfulness: as a process that helps make students more aware; as a process of self-knowledge; and as a process aimed at expanding the unconditioned consciousness of students and teachers. [ABSTRACT FROM AUTHOR]

The formation of molecular hydrogen as well as the possibility of using coinage metal hydrides as a prospective complex to produce hydrogen was presented in this work. Therefore, the reactions involving the interaction between two coinage metal hydrides, MH (M=Cu, Ag and Au, homo and heterodimers), were studied. The free energy profiles corresponding to aforementioned complexation were analysed by means of ab initio methods of quantum chemistry. The characteristics of these intermediates, final complexes and the electron density properties of the established interactions were discussed. [ABSTRACT FROM AUTHOR]

• A simplified mathematical model to describe combustion inside micro-rotary engines is proposed. • A numerical model based on high-order meshfree RBF-FD discretizations is developed. • Several benchmarks demonstrate the accuracy and effectiveness of our approach. • It aims to be instrumental in providing the needed understanding to produce more reliable micro-combustion systems. New micro-devices, such as unmanned aerial vehicles or micro-robots, have increased the demand of a new generation of small-scale combustion power system that go beyond the energy-density limitations of batteries or fuel cells. The characteristics short residence times and intense heat losses reduce the efficiency of combustion-based devices, a key factor that requires of an acute modelling effort to understand the competing physicochemical phenomena that hamper their efficient operation. With this objective in mind, this paper is devoted to the development of a high-order meshfree method to model combustion inside complex geometries using radial basis functions-generated finite differences (RBF-FD) based on polyharmonic splines (PHS) augmented with multivariate polynomials (PHS+poly). In our model, the combustion chamber of a micro-rotary engine is simulated by a system of unsteady reaction-diffusion equations coupled with a steady flow passing a bidimensional stenotic channel of great slenderness. The conversion efficiency is characterized by identifying the different combustion regimes that emerged as a function of the ignition point. We show that PHS+poly based RBF-FD is able to achieve high-order algebraic convergence on scattered node distributions, enabling for node refinement in key regions of the fluid domain. This feature makes it specially well adapted to integrate problems in irregular geometries with front-like solutions, such as reactive fronts or shock waves. Several numerical tests are carried out to demonstrate the accuracy and effectiveness of our approach. [ABSTRACT FROM AUTHOR]

Chloride complexes of gold(I) (seventeen) and gold(III) (seventeen) with different ligands (including H, C, N, O, P, S as interacting atoms) have been studied at the CCSD(T)/CBS level. The computed geometries were compared with those found in the Cambridge Structural Database and the dissociation energies related with those previously reported in the literature by Yamamoto et al. Some special processes catalysed by these gold complexes such as bond-breaking (dihydrogen, cyclopropane) and arenes reactivity were studied in detail. [ABSTRACT FROM AUTHOR]

The absorption and emission spectra of Yb2+-doped SrCl2 have been calculated on the basis of ab initio quantum chemical calculations which consider recently found, unexpected excited states with double-well energy curves and complex electronic structure, resulting from avoided crossings between Yb-trapped excitons and Yb impurity states, which influence prominent spectral features. The root mean square deviation and largest absolute error of the calculated energy levels are 394 and -826 cm-1, respectively. The YbCl8 moiety breathing mode vibrational frequencies and bond lengths of the lowest states are consistent with observed vibrational progressions and energy shifts induced by uniaxial compression. Photoionization is predicted above 49 000 cm-1 as a consequence of the spin-orbit induced spreading of the Yb-trapped exciton character in the upper part of the spectrum and three new emission bands are predicted with origins at about 33 800, 36 400, and 43 600 cm-1. The electron correlation methods used overestimate the relative stabilization of the 4f14 ground state and this leads to a constant error of the whole absorption spectrum of about 3500 cm-1 (23%-7%). Although this energy shift is customarily considered an adjustable parameter, it is a nonparametric, direct product in an ab initio route which shows the limitations on the proper representation of differential correlation between the 4fN and 4fN-15d (or similar) configurations and the need for theoretical improvement. [ABSTRACT FROM AUTHOR]

First-principles electronic structure calculations of the excited states of Yb2+-doped SrCl2 crystals up to 65 000 cm-1 reveal the existence of unexpected excited states with double-well potential energy surfaces and dual electronic structure lying above and very close in energy to the 4f135d manifold, with which they interact strongly through spin-orbit coupling. The double-well energy curves result from avoided crossings between Yb-trapped exciton states (more stable at short Yb-Cl distances) and 4f136s impurity states (more stable at long Yb-Cl distances); the former are found to be preionization states in which the impurity holds the excited electron in close lying empty interstitials located outside the YbCl8 moiety. Spin-orbit coupling between the double-well states and the lower lying 4f135d impurity states spreads the dual electronic structure character to lower energies and, hence, the instability of the divalent oxidation state is also spread. To some extent, the dual electronic structure (impurity-trapped exciton-impurity state) of some excited states expresses and gives support to hypotheses of interaction between Yb2+ and Yb3+ pairs proposed to understand the complex spectroscopy of the material and conciliates these hypotheses with interpretations in terms of the existence of only one type of Yb2+ defect. The results presented confirm the presence of impurity states of the 4f136s configuration among the 4f135d manifolds, as proposed in literature, but their energies are very different from those assumed. The Yb-trapped excitons found in this chloride host can be seen as precursors of the luminescent Yb-trapped excitons characterized experimentally in the isomorphous SrF2 crystals. [ABSTRACT FROM AUTHOR]

The lowest part of the 4f→5d absorption spectrum of Yb2+-doped CsCaBr3 crystals has been calculated using methods of quantum chemistry and it is presented here. A first, low-intensity band is found on the low energy side of the spectrum, followed by several strong absorption bands, in agreement with experimental observations in trivalent and divalent lanthanide ions of the second half of the lanthanide series, doped in crystals. Based on Hund’s rule, these transitions are usually interpreted as “spin-forbidden” and “spin-allowed” transitions, but this interpretation has been recently questioned in the literature. Here, a two-step relativistic method has been used which reveals the spin composition of the excited state wave functions. The forbidden band is found to be due to spin-forbidden transitions involving “high-spin” excited states because their 1 3T1u character is 90%. However, the allowed bands cannot be described as spin-allowed transitions involving “low-spin” excited states. Rather, they correspond to “spin-enabled” transitions because they get their intensity from limited (smaller than 45%) electric dipole enabling low-spin 1T1u character. Calculations using a spin-free Hamiltonian revealed that the difference in their electronic structures is related to the fact that the 4f135d(t2g)1 manifold is split by an energy gap which separates the lowest (high-spin) 1 3T1u from the rest of terms, which, in turn, lie very close in energy from each other. As a consequence, the lowest spin-orbit components of 1 3T1u are shown to remain 90% pure when spin-orbit coupling is considered, whereas a strong spin-orbit coupling exists between the remaining 4f135d(t2g)1 terms, among which the 1–3 1T1u enabling ones lie. As a result, there is a widespread electric dipole enabling 1T1u character, which, although never higher than 45%, leads to a number of spin-enabled absorption bands. [ABSTRACT FROM AUTHOR]

We present a linear stability analysis of the Richtmyer-Meshkov instability that develops when a shock wave reaches a sinusoidally perturbed premixed flame from behind. In the hydrodynamic regime, when acoustic contributions dominate the flame growth rate, the problem is analytically addressed by the direct integration of the sound wave equations at both sides of the flame, which are bounded by the reflected and transmitted shock waves and the flame front that acts as a contact surface in the hydrodynamic limit. The resolution involves: a hyperbolic change of variables to modify the triangular spatio-temporal domain, a transformation in the Laplace variable, the resolution of the functional equations in the frequency domain, and the final inverse Laplace transform. The latter involves a novel resolution method that is proven beneficial for long-time dynamics. Asymptotic analysis is also carried out to describe the early time and late time hydrodynamic response. The nonuniform flow field resulting from distorted oscillating shocks is characterized by acoustic, rotational, and entropic disturbances, each of which exerts a substantial influence on flame dynamics. These disturbances contribute to the intricate interplay of factors shaping the behavior of the flame in response to the nonuniform flow. In particular, the sensitivity of local flame propagation to temperature disturbances is investigated. This work contributes to a deeper understanding of Richtmyer-Meshkov instability dynamics and offers insights into instability reduction through the modulation of temperature disturbances generated by the transmitted shock. • Introduction of a self-consistent analytical model for Richtmyer-Meshkov instability within shock-flame interactions. • Development of an enhanced resolution method for the functional equation in the Laplace variable. • Introduction of a new resolution method for the transient evolution via the inverse Laplace transform. • Provision of a comprehensive mechanism regarding Richtmyer-Meshkov instability reduction. [ABSTRACT FROM AUTHOR]

Power generation usually requires removal of thermal energy from the system. In this paper, we evaluate the impact of the heat removal on the dynamics of a premixed flame in the case of a simple, but representative, counter-current microburner. In this configuration, two opposed streams of fresh gases with the same equivalence ratio ϕ are introduced, at the same velocity UF, in the burner through narrow, infinitely long channels. The channels are separated by the common wall from which the heat used for power generation is removed. A flame-sheet chemistry model and a realistic, specifically developed, one-step Arrhenius kinetics are used and compared in order to explore the importance of finite-rate chemistry effects. Finite-rate is found to play a significant role especially near the extinction limit (low velocities) and at high temperatures (high velocities) where distributed reaction can lead to autoignition. The changes in the flame stabilization position and operation limits of the burner are analyzed. Significant variations in combustor operation were found when energy is extracted from the system. Power generation efficiency is also studied, to conclude that an optimum level of energy extraction exists for each equivalence ratio and also that an optimum equivalence ratio exists. [ABSTRACT FROM AUTHOR]

Gold(I) complexes containing stabilising ligands such as phosphines or N -heterocyclic carbenes (NHCs) are known to be inhibitors of the enzyme thioredoxin reductase (TrxR) and therefore act as potential apoptosis-inducing anticancer drug candidates. The conjugation of biomolecules overexpressed in cancer cells to the gold complexes makes them semi-targeted metabolites. Auranofin, an anti-arthritis agent, encompasses this property and exhibits anti-tumour activities. The synthesis, characterization and biological evaluation of four novel N -heterocyclic carbene-gold(I)-thiosugar complexes derived from glucose, lactose and galactose is reported. The reactions of 1,3-dibenzyl-4,5-diphenyl-imidazol-2-ylidene gold(I) chloride (NHC∗-Au-Cl) with pre-synthesized glycosyl thiols under mildly basic conditions gave the desired NHC-Au-thiosugar complexes in high to excellent yields (79–91%). The complexes retain the strong and redox-active Au-S bond contained in Auranofin. All complexes showed good solubility in biological media and were tested against the NCI 60 cancer cell panel for cytotoxicity. The synthesized NHC∗-Au derivatives showed good activity in the medium to low micromolar region, while complex 2 showed activity in the low micromolar to nanomolar region against the tested cell lines. To provide a theoretical structure of 4 , computational calculations were carried out based on the crystal structures of NHC-Au-SCN and NHC-Au-S-C 6 H 4 OMe. [ABSTRACT FROM AUTHOR]

A 1 H NMR study shows the presence of intermolecular hydrogen bonds for AHLs in CDCl 3 solution. A detailed computational study of the structure of AHLs and the relative stability between the extended conformations ( X ) and those showing n → π* interactions ( np ) have been carried out by means of DFT calculations. Solvent effects have been shown to be very important when stabilising np conformations, particularly with polar solvents. This was shown by the shortening of C⋯O intramolecular distances and the increase in the relative energies favouring the np conformation with the dielectric constant of the solvent. The charge transfer between the O donor and the acceptor carbonyl group, assessed by second order perturbation energies, E(2), also shows an increase in the E(2) values with the dielectric constant of the solvent. [ABSTRACT FROM AUTHOR]

A series of potential anion transporters, dithieno[3,2-b;2',3'-d]thiophenes (DTT), involving anion-chalcogen interactions have been studied by analyzing the interaction energy, geometry and charge transfer. It was found that gas phase calculations show very negative interaction energies with short anion-chalcogen distances, but when solvent effects are considered, the interaction energy values decreased drastically concomitantly with an elongation on the interatomic distances. To enhance the chalcogen interaction between the DTT derivatives and the anion, increasing the anion transporter capacity, bisisothioazole moiety was considered; i.e., the σ-hole of the chalcogen atom was modulated by substitution of the adjacent carbon by a nitrogen atom in the S-C axis, increasing the depth of the σ-hole and therefore the interaction between the chalcogen and anion. Finally, different anions were analyzed within the complexes, finding that F- and NO3- would be the best candidates to form complexes and possibly displace other anions such as Cl- or Br-. [ABSTRACT FROM AUTHOR]

Forty-two peri-substituted naphthalene derivatives presenting chalcogen weak interactions were studied. They correspond to O···Y interactions, Y being O, S, and Se. While the O atom bears H or CH3 substituents (OH and OCH3 groups), the Y atom is substituted by H, F, and CN to explore the effect of these electron-donating and electron-withdrawing substituents on the chalcogen bond strength. The effect of F and CH3 substituents on positions ortho/para (2,4,5,7 of the naphthalene ring) was also studied. Optimizations were performed at the MP2/aug-cc-pVDZ, and binding energies were performed at the MP2/aug-cc-pVDZ followed by an MP2/CBS estimation. The main properties studied were geometries, energies (Eb, Eiso, and Edef), the molecular electrostatic potential, electron density shifts, natural bond order E(2) energies, and the relationship between these properties. [ABSTRACT FROM AUTHOR]

We examine in this work the effect of an external electric field on the propagation velocity of a laminar, one-dimensional and lean premixed flame, with the final goal of clarifying the relative importance of each of the three different mechanisms postulated in the literature to explain the effect of electric fields on flames: ionic wind, kinetic enhancement by non-thermal electrons and ohmic heating. The one-dimensional model proposed here expands the four-reactions scheme previously presented by Sánchez-Sanz, et al. (2015) to include the effect of non-thermal electrons and activated neutral molecules on flame acceleration. Two additional reactions are included in the model to complete a minimum set of six elementary reaction capable of qualitatively reproduce the results observed in classical (Jaggers, and Von Engel, (1971).) and recent (Volkov et al., 2013; Murphy, et al., 2014,) experiments. The limit of weakly ionized plasmas is used to integrate the Boltzmann equation and to derive an explicit expression for the electron temperature proportional to the square of the electric field. The numerical integration of the conservation equations gives the flame propagation velocity for a given set of parameters. The results reveal the importance of the electric field polarity on flame acceleration, finding faster flames for positive electric fields than for equally intense negative fields. At low-intensity fields, our results indicate that the ionic wind, and the associated redistribution of the charged particles, is the main mechanism inducing flame acceleration. In more intense fields, the combined effect of the ionic wind and the heat transfer from the high-temperature electrons to the background gas induces a significant increase in the temperature field upstream and downstream of the flame front. Associated with this temperature increase, relevant changes on the flame speed are computed for positive, intense electric fields, while only modest flame accelerations are observed for equally intense negative fields, behavior that reproduces qualitatively the measurements by Murphy et al. (2014). The reduced sensitivity to an external electric field when the mixture approaches stoichiometry, observed experimentally by Jaggers, and Von Engel (1971) and Fang et al. (2015), is also reproduced by the model proposed in this work. [ABSTRACT FROM AUTHOR]

A computational study of the aromatic and antiaromatic characteristics of closed shell charged phenalenyl (PLY and PLY) upon replacement of the central carbon atom by icosagen (B, Al and Ga), tetrel (Si and Ge) and pnictogen (N, P and As) atoms comprising systems in which the icosagen and pnictogen derivatives considered are neutral while the tetrel ones are anions or cations, has been carried out at the B3LYP/6-311++G(d,p) computational level. By substitution, two different kinds of structures have been obtained, one planar (N and B) and another one bowl-shaped depending on the size of the central atom. In terms of aromaticity, the substitution of the central C atom causes a loss of the aromatic character in all cases as indicated by nucleus-independent chemical shifts (NICS) profiles and NICS values on the 0.001 au isosurface. Regarding the charge, PLY presents larger electron delocalisation than PLY, phenomenon associated with aromaticity. Furthermore, the current density maps for those planar systems corroborate NICS findings, showing anticlockwise currents in PLY (like in benzene) but clockwise in PLY-N and PLY-B, indicating aromatic and antiaromatic behaviour, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • A flexible and deformable electrochemical sensor to detect dopamine is developed. • The sensor consists on a membrane made of alternated layers of PLA and PEDOT. • Spin-coated nanoperforated PLA layers allow to electropolymerize PEDOT layers. • The self-supported membrane acts directly as electrode, detecting dopamine. • Sensing is within the range of concentrations found for specific types of cancer. In addition of a key catecholamine neurotransmitter, dopamine is is the metabolite predominantly produced by specific types of tumors (e.g. paragangliomas and neuroblastomas), which cannot be diagnosed using conventional sensitive tests. Within this context, development of flexible electrochemical sensors to monitor dopamine levels in physiological fluids for the early diagnosis and control of diseases related to abnormal levels of such compound, is necessary. In this work, a flexible self-supported membrane, which acts directly as electrode, has been developed to detect dopamine. The membrane consists of three nanoperforated polylactic acid (PLA) layers, which provide flexibility and mechanical integrity, separated by two layers of an electroactive copolymer, which are obtained by electrochemical copolymerization of 3,4-ethylenedioxythiophene and aniline. The sensitivity and detection limit provided by the electroactive copolymer, which is accessible to dopamine molecules through the nanoperforations of the PLA outer layers, is 1.846 µA/(cm2·µM) and 1.7 µM, respectively, in a urea-rich environments that mimics urine. These values allow us to propose the self-standing flexible electrodes developed in this study for the detection of dopamine in patients affected by paragangliomas and neuroblastomas tumors, which typically present dopamine concentrations between 2 and 7 μM. [ABSTRACT FROM AUTHOR]

A theoretical study of the peri interactions, both intramolecular hydrogen (HB) and chalcogen bonds (YB), in 1-hydroxy-8YH-naphthalene, 1,4-dihydroxy-5,8-di-YH-naphthalene, and 1,5-dihydroxy-4,8-di-YH-naphthalene, with Y = O, S, and Se was carried out. The systems with a OH:Y hydrogen bond are the most stable ones followed by those with a chalcogen O:Y interaction, those with a YH:O hydrogen bond (Y = S and Se) being the least stable ones. The electron density values at the hydrogen bond critical points indicate that they have partial covalent character. Natural Bond Orbital (NBO) analysis shows stabilization due to the charge transfer between lone pair orbitals towards empty Y-H that correlate with the interatomic distances. The electron density shift maps and non-covalent indexes in the different systems are consistent with the relative strength of the interactions. The structures found on the CSD were used to compare the experimental and calculated results. [ABSTRACT FROM AUTHOR]

RASSF enzymes act as key apoptosis activators and tumor suppressors, being downregulated in many human cancers, although their exact regulatory roles remain unknown. A key downstream event in the RASSF pathway is the regulation of MST kinases, which are main effectors of RASSF-induced apoptosis. The regulation of MST1/2 includes both homo- and heterodimerization, mediated by helical SARAH domains, though the underlying molecular interaction mechanism is unclear. Here, we study the interactions between RASSF1A, RASSF5, and MST2 SARAH domains by using both atomistic molecular simulation techniques and experiments. We construct and study models of MST2 homodimers and MST2-RASSF SARAH heterodimers, and we identify the factors that control their high molecular stability. In addition, we also analyze both computationally and experimentally the interactions of MST2 SARAH domains with a series of synthetic peptides particularly designed to bind to it, and hope that our approach can be used to address some of the challenging problems in designing new anti-cancer drugs. [ABSTRACT FROM AUTHOR]

A computational study of the aromatic characteristics of phenalenyl (PLY) upon replacement of the central carbon atom by Si, Ge, N, P, As, B, Al and Ga atoms comprising isoelectronic series with different charges (0, +1, −1) has been performed at the B3LYP/6-311++G(d,p) level. Two different geometries have been obtained, one planar and another one bowl-shaped. PLY derivatives exhibit a loss of the aromatic character in all cases indicated by NICS (Nucleus-Independent Chemical Shifts) values. These aromatic features are also in agreement with the pyramidalisation undergone by the central atom. The current density maps for those planar systems corroborate NICS findings. These variations in the aromaticity have been rationalised in terms of charge localisation. Harmonic oscillator model of aromaticity (HOMA) and para -delocalisation indices (PDI) have been used to evaluate the electron density delocalisation. HOMA values do not correlate with NICS but PDI indices follow the same trend than NICS. [ABSTRACT FROM AUTHOR]

A multipurpose reduced chemical-kinetic mechanism for methanol combustion comprising 8 overall reactions and 11 reacting chemical species is presented. The development starts by investigating the minimum set of elementary reactions needed to describe methanol combustion with reasonable accuracy over a range of conditions of temperature, pressure, and composition of interest in combustion. Starting from a 27-step mechanism that has been previously tested and found to give accurate predictions of ignition processes for these conditions, it is determined that the addition of 11 elementary reactions taken from its basis (San Diego) mechanism extends the validity of the description to premixed-flame propagation, strain-induced extinction of non-premixed flames, and equilibrium composition and temperatures, giving results that compare favourably with experimental measurements and also with computations using the 247-step detailed San Diego mechanism involving 50 reactive species. Specifically, premixed-flame propagation velocities and extinction strain rates for non-premixed counterflow flames calculated with the 38-step mechanism show departures from experimental measurements and detailed-chemistry computations that are roughly on the order of 10%, comparable with expected experimental uncertainties. Similar accuracy is found in comparisons of autoignition times over the range considered, except at very high temperatures, under which conditions the computations tend to overpredict induction times for all of the chemistry descriptions tested. From this 38-step mechanism, the simplification is continued by introducing steady-state approximations for the intermediate species CH3, CH4, HCO, CH3O, CH2OH, and O, leading to an 8-step reduced mechanism that provides satisfactory accuracy for all conditions tested. The flame computations indicate that thermal diffusion has a negligible influence on methanol combustion in all cases considered and that a mixture-average species-transport model is sufficiently accurate for premixed and non-premixed flames, whereas for the former an even simpler constant-Lewis-number description gives equally satisfactory results. [ABSTRACT FROM AUTHOR]

With the aim of applying numerical methods, we develop a formalism for physiologically structured population models in a new generality that includes consumer-resource, cannibalism and trophic models. The dynamics at the population level are formulated as a system of Volterra functional equations coupled to ODE. For this general class, we develop numerical methods to continue equilibria with respect to a parameter, detect transcritical and saddle-node bifurcations and compute curves in parameter planes along which these bifurcations occur. The methods combine curve continuation, ODE solvers and test functions. Finally, we apply the methods to the above models using existing data for Daphnia magna consuming Algae and for Perca fluviatilis feeding on Daphnia magna. In particular, we validate the methods by deriving expressions for equilibria and bifurcations with respect to which we compute errors, and by comparing the obtained curves with curves that were computed earlier with other methods. We also present new curves to show how the methods can easily be applied to derive new biological insight. Schemes of algorithms are included. [ABSTRACT FROM AUTHOR]

The detailed, atomistic-level understanding of molecular signaling along the tumor-suppressive Hippo signaling pathway that controls tissue homeostasis by balancing cell proliferation and death through apoptosis is a promising avenue for the discovery of novel anticancer drug targets. The activation of kinases such as Mammalian STE20-Like Protein Kinases 1 and 2 (MST1 and MST2)--modulated through both homo- and heterodimerization (e.g. interactions with Ras association domain family, RASSF, enzymes)--is a key upstream event in this pathway and remains poorly understood. On the other hand, RASSFs (such as RASSF1A or RASSF5) act as important apoptosis activators and tumor suppressors, although their exact regulatory roles are also unclear. We present recent molecular studies of signaling along the Ras-RASSF-MST pathway, which controls growth and apoptosis in eukaryotic cells, including a variety of modern molecular modeling and simulation techniques. Using recently available structural information, we discuss the complex regulatory scenario according to which RASSFs perform dual signaling functions, either preventing or promoting MST2 activation, and thus control cell apoptosis. Here, we focus on recent studies highlighting the special role being played by the specific interactions between the helical Salvador/RASSF/Hippo (SARAH) domains of MST2 and RASSF1a or RASSF5 enzymes. These studies are crucial for integrating atomistic-level mechanistic information about the structures and conformational dynamics of interacting proteins, with information available on their system-level functions in cellular signaling. [ABSTRACT FROM AUTHOR]

A theoretical study of the competition between hydrogen (HB) and pnictogen bonds (ZB) in three different families of compounds, (Z)-1,2-disubstituted ethenes (Eth), 1,2-disubstituted benzenes (Phe) and 1,8-disubstituted naphthalenes (Naph), with a charged group, ZH3+ and a neutral one, Z′H2 (Z, Z′ = N, P, As) as interacting moieties, has been carried out. In those structures with a NH3+ motif, intramolecular hydrogen bond structures are minima while pnictogen interactions are transition states. The opposite is true for PH3+ and AsH3+ moieties. An analysis of isodesmic energies (Eiso), interaction energies (Eb) and deformation energies (Edef) shows that in Eth derivatives, the most stable compound corresponds to P+–N ZB while in the Phe and Naph ones, the N+–N HB interaction presents the largest negative isodesmic energy. Also, Eth and Phe derivatives show negative Eiso values for all the compounds under study; however, in some cases of Naph derivatives positive isodesmic energies have been found. The Atoms in Molecules (AIM) analysis of the electron density, natural bond orbital (NBO) second-order orbital energies and electron density shift maps (EDS) have been used to better understand these intramolecular interactions. [ABSTRACT FROM AUTHOR]

A theoretical study of the XNO2 homodimers (X = F, Cl, Br and I) has been carried out by means of the Møller–Plesset (MP2) methodology. Twenty-two different minimum structures have been found, involving pnictogen, chalcogen and halogen bonds. MP2 interaction energies range between −0.4 to −17.5 kJ mol−1. Atoms in molecules (AIM) and natural bond orbital (NBO) approaches have been used to analyse the nature of the interaction within both monomers, obtaining good correlations between Laplacian values and bond distances. NBO E(2) orbital interaction energies are found to be up to 39.0 kJ mol−1. Charge transfer between monomers is in agreement with those in AIM and NBO findings, showing the highest charge transferred in those asymmetric dimers which involve pure halogen bonds. Symmetry adapted perturbation theory (SAPT-DFT) results show that the interactions are driven by the dispersion term, followed by the electrostatic one. The induction term presents the lowest contribution with the exception of complexes 1 and 5 of the iodine derivative in which ESTACKABOVE(2)/ABOVEBELOWi/BELOW/STACK shows the maximum contribution to the total forces. [ABSTRACT FROM AUTHOR]

A thorough study of the structural and aromatic properties of derivatives of benzene and naphthalene where one or more –CH– groups have been substituted by a nitrogen, phosphorous or arsenic atom has been carried out at B3LYP/6-311++G(d,p) level. Relative energies between isomers range from 5.0 to 294 kJ mol −1 finding the largest relative energies in compounds with nitrogen substitutions. In general, most of the compounds show to be planar with a few exceptions, which exhibit twisted structures. Wiberg bond indexes as well as bond distances indicate that in almost all the cases the bond nature is benzene-like. Aromatic characteristics have been addressed calculating NICS values, profiles, isosurfaces and HOMA indexes. NICS(1) and (2) present values close to those of benzene showing aromatic behaviour, confirmed by NICS profiles and 3D NICS isosurfaces. HOMA indexes obtained for those compounds with reported parameterized bonds are in agreement with their corresponding aromatic nature. [ABSTRACT FROM AUTHOR]

Mechanistic studies of the reaction between 3-arylprop-2-ynyl esters and aldehydes catalyzed by BF3 ⋅Et2O were performed by isotopic labeling experiments and quantum chemical calculations. The reactions are shown to proceed by either a classical alkyne-carbonyl metathesis route or an unprecedented addition-rearrangement cascade. Depending on the structure of the starting materials and the reaction conditions, the products of these reactions can be Morita-Baylis-Hillman (MBH) adducts that are unavailable by traditional MBH reactions or E- and Z-α,β-unsaturated ketones. 18O-Labeling studies suggested the existence of two different reaction pathways to the products. These pathways were further examined by quantum chemical calculations that employed the DFT(wB97XD)/6-311+G(2d,p) method, together with the conductor-like screening model for realistic solvation (COSMO-RS). By using the wB97XD functional, the accuracy of the computed data is estimated to be 1-2 kcal mol−1, shown by the careful benchmarking of various DFT functionals against coupled cluster calculations at the CCSD(T)/aug-cc-pVTZ level of theory. Indeed, most of the experimental data were reproduced and explained by theory and it was convincingly shown that the branching point between the two distinct mechanisms is the formation of the first intermediate on the reaction pathway: either the four-membered oxete or the six-membered zwitterion. The deep mechanistic understanding of these reactions opens new synthetic avenues to chemically and biologically important α,β-unsaturated ketones. [ABSTRACT FROM AUTHOR]

Abstract: The effect of the equivalence ratio on the stability and dynamics of a premixed flame in a planar micro-channel with a step-wise wall temperature profile is numerically investigated using the thermo-diffusive approximation. To characterize the stability behavior of the flame, we construct the stability maps delineating the regions with different flame dynamics in the inlet mass flow rate m vs. the equivalence ratio parametric space. The flame stability is analyzed for fuels with different diffusivity by changing the Lewis numbers in the range . On the other hand, the Lewis number of the oxidizer is kept constant and equal to unity . Our results show that, for very diffusive fuels, the stability of the flame varies significantly with the equivalence ratio, transitioning from stable flames for lean mixtures to highly unstable flames when . As the fuel Lewis number approaches unity, the stability behavior of the flame for lean and rich mixtures becomes more similar to give, in the equidiffusional case , a symmetric stability map around the stoichiometric mixture . In all cases considered, the most stable flames are always found around the stoichiometric mixtures , when the flame instabilities are completely suppressed for very diffusive fuels , or are reduced to a narrow range of inflow velocities for fuel Lewis numbers equal or greater than unity. The ratio between the size of the channel and the flame thickness d turns out to be of great importance in the stability behavior of the flame. Keeping the rest of parameters constant, an increase in d for lean flames makes the flame considerably more unstable, confirming the findings of previous works. Nevertheless, as the stoichiometric ratio approaches , that trend is reversed to give flames that become more stable as the size of the channel is increased. [Copyright &y& Elsevier]

Invited for this month's cover picture is the group of Dr. Cristina Trujillo at the Trinity Biomedical Sciences Institute in Dublin (Ireland) and Prof. Ibon Alkorta at the CSIC in Madrid (Spain). The cover picture shows the possibility of reversibly storing hydrogen using metallic compounds as reactants to produce H2 gas and metallic dimers. Computational studies have been carried out to investigate these processes, as shown in the concept art by the Schrödinger equation. It was found that the formation and release of H2 is energetically favorable. These results are a promising starting point for further research of using coinage metals for storing hydrogen in light compounds. Read the full text of their Full Paper at10.1002/open.202100108. [ABSTRACT FROM AUTHOR]

Abinitio MP2/aug′-cc-pVTZ calculations have been carriedout to investigate the pnicogen bonded complexes formed between theacids OPH3, SPH3, HNPH3, and H2CPH3and the bases NH3, NCH, N2, PH3, and PCH. All nitrogenand phosphorus bases form complexes in which the bases are lone pairelectron donors. The binding energies of complexes involving the strongerbases NH3, NCH, and PH3differentiate amongthe acids, but the binding energies of complexes with the weaker basesdo not. These complexes are stabilized by charge transfer from thelone pair orbital of N or P to the σ*PA orbital of XPH3, where A is the atom of X directly bonded to P. PCH alsoforms complexes with the XPH3acids as a πelectron donor to the σ*PA orbital. The binding energiesand the charge-transfer energies of the π complexes are greaterthan those of the complexes in which PCH is a lone pair donor. Whetherthe positive charge on P increases, decreases, or remains the sameupon complex formation, the chemical shieldings of 31Pdecrease in the complexes relative to the corresponding monomers. 1pJ(P–N) and 1pJ(P–P) values correlate best with the corresponding P–Nand P–P distances as a function of the nature of the base. 1J(P–A) values do not correlate withP–A distances. Rather, the absolute values of 1J(P–O), 1J(P–S),and 1J(P–N) decrease upon complexation.Decreasing 1J(P–A) values correlatelinearly with increasing complex binding energies. In contrast, 1J(P–C) values increase upon complexationand correlate linearly with increasing binding energies. [ABSTRACT FROM AUTHOR]

Highlights: [•] Open-chain and cyclic structures of malonaldehyde enol were compared. [•] Catemers up to 9 monomers have been calculated. [•] Bader QTAIM analysis was used to understand the structures. [•] NMR properties, 1H chemical shifts and 2h J OO coupling constants, were analyzed. [ABSTRACT FROM AUTHOR]

Abstract: Continuing with our interest in aromaticity, we have studied the influence that replacement of formal C–C single bonds by C–C C–C fragments, in a series of mono- (cyclobutadiene, benzene, and cyclooctatetraene) and fused-carbocycles (naphthalene and azulene), has in their properties, focusing mostly on NMR and aromaticity. We have analyzed the effect of such substitution not only in the aromaticity of the different structures, but also in the influence of low and high spin states by means of NICS values over the rings and 3D NICS isosurfaces. We have found that, in most of the cases, the substitution induces a loss of aromaticity in singlet states (both restricted and unrestricted) that can be recovered when triplet states are taken into account. [Copyright &y& Elsevier]

Theoretical calculations at the B3LYP/6-311++G(d,p) level have been carried out on the reaction path connecting a dipeptide to an imidazolinone as a model for the formation of GFP. In addition, we have studied the hydration effects on the processes, adding a water molecule to assist the cyclization. The solvent effects have been taken into account by introducing the monohydrated molecules into a solvent cavity with a polarized continuum model. Significant reductions of the energy barriers for the reaction path can be observed within the water-assisted processes. The solvent effects account for a barrier lowering of 4-5 kJ mol. [ABSTRACT FROM AUTHOR]

We have calculated the complexes formed by guanidine/guanidinium and HCl/Cl−, HNO3/NO3− and H2SO4/HSO4− both in the gas and aqueous Polarizable Continuum Model (PCM) phase to understand the effect that solvation has on their interaction energies. In the gas phase, the cation-anion complexes are much more stable than the rest; however, when PCM-water is considered, this energetic difference is not as large due to the extra stabilization that the ions suffer when in aqueous solution. All the complexes were analyzed in terms of their AIM and NBO properties. In all cases, water solvation seems to 'dampen' those properties observed in the gas phase. The values of Nucleus Independent Chemical Shift (NICS)(1) and NICS(2) indicate a huge influence of the proximity of the carbon atom for short distances; thus, the 3D NICS values on the van der Waal isosurfaces have been used to evaluate the possible Y-aromaticity of the guanidinium system. The isosurface in this system is more similar to cyclohexane than to benzene as indication of poor aromaticity. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical analysis the effect of non-covalent interactions (NCI) in three different SN2 reactions (X–:CH3X → XCH3:X–, X = Cl, Br and I) has been theoretically analysed in the pre-reactive complexes, TS and products. A total of eighteen Lewis acids (LAs: FH, ClH, FCl, I2, SeHF, SeF2, PH2F, PF3, SiH3F, SiF4, BH3, BF3, BeH2, BeF2, LiH, LiF, Au2 and AgCl) interact with the halogen atom of the CH3X molecule. To analyse the strength of the non-covalent interactions, both the independent gradient model tool and electron density maps have been employed. The results reveal that in all cases, the interaction between the anion and the Lewis acid leads to an increase in the transition barriers compared to the parental reaction. [ABSTRACT FROM AUTHOR]

An ab initio MP2/aug’-cc-pVTZ study has been carriedoutto identify local minima on the (NH2F)2, H2FP:NFH2, and (PH2F)2potentialsurfaces, to characterize the types of interactions which stabilizethe complexes found at these minima, and to evaluate their bindingenergies. With one exception, (NH2F)2complexesare stabilized by N–H···N or N–H···Fhydrogen bonds. Only one complex, that with the smallest binding energy,has a pnicogen N···N bond. In contrast, (PH2F)2complexes are stabilized by P···P orP···F pnicogen bonds or by an antiparallel alignmentof the dipole moment vectors of the two monomers, but not by hydrogenbonds. The most stable complex has an F–P···P–Falignment which approaches linearity. Both hydrogen-bonded and pnicogen-bondedcomplexes exist on the H2FP:NFH2surface, withthe most stable being the pnicogen-bonded complex with F–P···N–Fapproaching a linear arrangement. Charge transfer transitions froma lone pair on a P, N, or F atom in one molecule to an antibondingσ* orbital of the other stabilize these complexes. These transitionsare most important for complexes with pnicogen bonds. Although netcharge transfer occurs in complexes in which the two monomers areinequivalent, charges on N and P do not correlate with N and P absolutechemical shieldings. Rather, these shieldings also reflect chargedistributions and overall bonding patterns. EOM-CCSD two-bond spin–spincoupling constants 2hJ(X–Y) acrossX–H···Y hydrogen bonds tend to be small, duein part to the nonlinearity of many of the hydrogen bonds. 1pJvalues across a particular kind of pnicogen bondare relatively large and vary significantly but do not correlate withcorresponding distances. [ABSTRACT FROM AUTHOR]

Abstract: The conditions that lead to the extinction of a premixed flame propagating along a channel of height 2h 1 ∼ δ T are studied using the thermo-diffusive approximation, with δ T = D T /S L , D T and S L representing, respectively, the thermal flame thickness, the thermal conductivity and the planar flame speed. It is found that flame propagation is greatly affected by conductive heat losses to the wall , where n denotes the transverse distance to the wall, T and T 0 are, respectively, the fluid’s and wall’s temperature and is the heat transfer parameter. The sensitivity of the flame to heat losses grows as the channel narrows, leading to complete flame extinction at extremely small values of . As a way to overcome flame quenching at the walls, Lloyd and Weinberg proposed the recirculation of part of the heat stored in the exhaust gases to preheat the cold combustible mixture. In order to understand the flame dynamics in the presence of heat recirculation, we analyze the problem of two parallel channels with a combustible mixture and an inert fluid moving in opposite directions, with maximum velocities m 1 and m 2 respectively, and where heat exchange is permitted through the common wall separating both channels. It is shown that flame extinction occurs if the velocity ratio m 2/m 1 is outside the range m 2/m 1 ∈[m 21,min m 21.max ], where the limiting values m 21,min and m 21.max are obtained numerically for a given set of parameters. The amplitude of this range depends, mainly, on the Damkhöler number d =[h 1/(D T /S L )]2, quantity that represents the ratio between the channel’s height h 1 and the thermal flame thickness D T /S L . It is shown that heat recirculation is capable of extending combustion to very small h 1, but there is still a minimum value of the Damkhöler number d min below which combustion is not possible. The evolution of d min is computed numerically to give values as small as d =0.0025 for a given combination of the geometric parameters of the problem. The maximum flame temperature computed in the parallel channel configuration rises above the adiabatic flame temperature T e due to the effect of the heat recirculation. This effect becomes more significant as d is reduced, leading to maximum temperatures close to T ≃1.4T e in very narrow channels. [Copyright &y& Elsevier]

Abstract: This work reports the theoretical study of the aromaticity of a series of carbocycles (benzene, cyclohexane, bent and planar cyclooctatetraene) and heterocycles (pyridine, furan, thiophene, pyrrole) and their didehydro forms (arynes and hetarynes). As aromaticity probe Schleyer''s NICS were used and represented in two 3D isosurfaces of the electron density. The spatial 3D representation of the NICS is shown to be a powerful tool to visualize the aromaticity (or its absence) of different molecules. [Copyright &y& Elsevier]

Theoretical calculations at the B3LYP/6-31G(d) level have been carried out on the isomerization of cyclic-tri-glycine into the corresponding tri-cyclol. The results confirmed that the cyclol hypothesis was untenable both from a thermodynamic as well as from a kinetic point of view. [ABSTRACT FROM AUTHOR]

Abstract: An azo derivative of 1H-pyrazole has been chosen to study the information obtained from different techniques for determining the structure of a non-crystalline compound in the solid-state and in solution. Syn–anti isomerism of the azo group, prototropic tautomerism of the 1H-pyrazole and rotation about the pyrazole–azo group resulted in 20 structures that were analyzed. Energy calculations, 13C and 15N chemical shifts, 1H–1H coupling constants and electronic spectra reduced the 20 possible structures to only one, the 3,3′-Z,Z-anti-azopyrazole. [Copyright &y& Elsevier]

Abstract: This paper investigates the conditions under which flame pinch-off occurs in forced and non-forced, buoyant laminar jet diffusion flames. The fuel jet emerges into a stagnant air atmosphere at temperature T 0, with a velocity that varies periodically in time with non-dimensional frequency ω l and amplitude A =0.5. We use the formulation developed by Liñán and Williams based on the combination of the mass fraction and energy conservation equations to eliminate the reaction terms, that are substituted by the mixture fraction Z and the excess-enthalpy H scalar conservations equations. With this formulation, valid for arbitrary Lewis numbers, the flame lies on the stoichiometric mixture fraction level surface Z = Z s and its temperature can be easily calculated as , where Z s =1/(1+ S), γ is the non-dimensional heat release parameter, S is the air needed to burn the unit mass of fuel and H s is the value of the excess enthalpy at the flame surface. Non-modulated flames ω l =0 subjected to a gravity field g are known to flicker at a non-dimensional frequency ω l,0 that depends on the Froude number Fr l . The surface of the flame is deformed by the buoyancy-induced oscillations and, for Froude numbers below a certain critical value , the flame breaks repeatedly in two different combustion regions (pinch-off). The first one remains attached to the burner and constitutes the main flame. The second region detaches from the tip of the flame, forming a pocket of hot gas surrounded by a flame that travels along the downstream coordinate z with velocity until the fuel inside the pocket is depleted. Pinch-off is affected by the modulation of the velocity of the jet, changing the critical Froude number of pinch-off Fr l,c as the excitation frequency ω l is modified. Very large ω l /ω l,0 ≫1 or very small ω l /ω l,0 ≪1 excitation frequencies do not modify Fr l,c and it remains equal to . For ω l /ω l,0 ∼ O(1), the response of the flame is determined by the ratio l/x g = γ/Fr l , where l represents the flame length and x g is the distance at which buoyancy effects become important. A strong resonance is observed at ω l ∼ ω l,0 if the flame is sufficiently long, giving Fr l,c that could be thirty times larger than . Short flames do not present that peak and Fr l,c remains almost independent of ω l . [Copyright &y& Elsevier]

The three parent NH-benzazoles, benzimidazole, indazole and benzotriazole, have been studied theoretically at the B3LYP/6-311++G(d,p) level. Optimized geometries have been compared with those obtained by X-ray crystallography, energies with studies about tautomerism, acidbase properties with pKas, and chemical shifts with those reported in the literature. As aromaticity probe, Schleyer's Nuclear Independent Chemical Shifts (NICS) were used and represented in two 3D isosurfaces of the electron density. [ABSTRACT FROM AUTHOR]

With ab initio MP2 computational methods, a theoretical study has been carried out to characterize the interaction between aliphatic cyclic hydrocarbons, as models of molecular hydrocarbon monolayers, with cations (Li+, Na+, and K+), anions (F-,CI-, and Br-), and both simultaneously in opposite faces of the hydrocarbons. In addition, the energetic barrier for the cation crossing through the hydrocarbon ring has been calculated. The hydrocarbons chosen for this study are cyclohexane (C6H12) and adamantane (C10H16). The energies obtained for the M+: hydrocarbon:X- complexes indicate positive cooperativity in the cases where the hydrocarbon is cyclohexane while diminutive effects are found in the adamantane complexes. The density functional theory-symmetry adapted perturbation theory analysis of the interaction energies shows that the most important term in the complexes with cations is the induction, while in the complexes with anion and with cations and anions simultaneously the most important term is the repulsion-exchange one. The electron density of the complexes has been analyzed using the atoms in molecules methodology and provides some insight to the electron transfer within the complexes. [ABSTRACT FROM AUTHOR]

A theoretical study of the HXYH (X, Y = O, S and Se) monomers and dimers has been carried out by means of MP2 computational methods. For the monomers, isomerization (H2X=Y//HXYH) and rotational transition state barriers have been calculated. Additionally, the molecular electrostatic potential of the isolated monomers has also been analysed. Due to the chiral nature of these compounds, homo and heterochiral dimers have been explored. The number of minima found for the dimers range between 13 and 22. The electron density of the complexes has been characterized with the Atoms in Molecules (AIM) methodology finding a large variety of interactions. The DFT-SAPT method has been used to analyse the components of the interaction energies. Concerning chalcogen–chalcogen interactions, although the most stable minima are formed through hydrogen bonds (especially if OH groups are present in the molecules) as the size of the atoms involved in the interaction increase, the chalcogen–chalcogen contacts become more important. [ABSTRACT FROM PUBLISHER]

Abstract: We present a concept for passive control of vortex induced vibration (VIV) that uses the body shape of a prismatic body as the control parameter in 2D internal flow. We consider that the Reynolds number based on the prism cross section height is 200 and that the blockage ratio of the channel is 2.5. The working fluid is water and the solid-to-fluid density ratio is 1, so that the prism presents neutral buoyancy and the body shape parameter acts as the only control parameter. Two very different fluid dynamics regimes are observed depending on with an abrupt transition between them for , where represents a critical value obtained numerically. For the cylinder oscillation is controlled by vortex shedding and represents a typical case of vortex induced vibration. For the oscillation is a mixture of galloping and vortex induced vibration that causes the prism motion to shift from a stable periodic motion to a highly irregular pattern. The physical explanation for the change of regime is given based on the cylinder equation of motion. [Copyright &y& Elsevier]

The planar and axisymmetric variable-density flows induced in a quiescent gas by a concentrated source of momentum that is simultaneously either a source or a sink of energy are investigated for application to the description of the velocity and temperature far fields in laminar gaseous jets with either large or small values of the initial jet-to-ambient temperature ratio. The source fluxes of momentum and heat are used to construct the characteristic scales of velocity and length in the region where the density differences are of the order of the ambient density, which is slender for the large values of the Reynolds number considered herein. The problem reduces to the integration of the dimensionless boundary-layer conservation equations, giving a solution that depends on the gas transport properties but is otherwise free of parameters. The boundary conditions at the jet exit for integration are obtained by analysing the self-similar flow that appears near the heat source in planar and axisymmetric configurations and also near the heat sink in the planar case. Numerical integrations of the boundary-layer equations with these conditions give solutions that describe accurately the velocity and temperature fields of very hot planar and round jets and also of very cold plane jets in the far field region where the density and temperature differences are comparable to the ambient values. Simple scaling arguments indicate that the point source description does not apply, however, to cold round jets, whose far field region is not large compared with the jet development region, as verified by numerical integrations. [ABSTRACT FROM AUTHOR]

Abstract: The inversion and rotation mechanisms for the isomerization of Feringa’s bithioxanthenes existing in two conformations, up/up and up/down, have been calculated at the B3LYP/6-31G(d) and B3LYP/6-311++G(d,p) levels. The inversion mechanism that maintains the double bond nature of the central bond is a classical one but the rotation mechanisms that break the double bond to form a biradical needs to explore the singlet and triplet states. To do this we have removed the four fused phenyl rings of bithioxanthene and calculated at the CASSCF and CASPT2 levels bis(4H-thiopyran) proving that B3LYP calculations yield reasonable results for the rotation barriers. [Copyright &y& Elsevier]

Abstract: Using density functional theory, coupled cluster and multireference methods, dissociation energies and 3rd ionization potentials for, respectively, triply charged and neutral carbon clusters have been evaluated. The results show that the smaller C n 3+ clusters are metastable, i.e., they present a fragmentation channel with negative dissociation energy. The lowest dissociation channel always corresponds to evaporation of a singly charged carbon atom. Good agreement with available experimental data is found for most two-fragment channels. The third ionization potential of the corresponding neutral species decreases with cluster size. [ABSTRACT FROM AUTHOR]