Density functional theory study of the oxidative dehydrogenation of propane on the (001) surface of V2O5

The density functional theory using a plane‐waves basis set and pseudopotential has been used to study the reaction pathways for ODH of propane on the V₂O₅(001) surface. The calculations indicated that propane adsoprtion step was initiated by the insertion of vanadyl oxygen O (1) into methylene C? H bond forming an iso‐propanol structure. This step is the rate‐determining step with an activation energy of 23.3 kcal/mol. The subsequent step involved the abstraction of the second hydrogen by O (1) site leading the formation of propene. This process had an activation energy of 22.5 kcal/mol. The elimination of surface bound water molecule at the O (1) was a barrierless process. The energy required for this process was compensated from O2 dissociative adsorption. Finally, the electronic density of state has been applied to prove the reality of the calculated results. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Extraction and isolation of catechins from tea

Tea is a major source of catechins, which have become well known for their antioxidant potential. Numerous human, animal, and in vitro studies have linked tea catechins with prevention of certain types of cancers, reduction of the risks for obesity, diabetes, and cardiovascular disease, and improvement of the immune system. Tea catechins are widely used in various neutraceuticals, pharmaceuticals, and cosmetics for either enhancing product shelf-life or for enhancing human health. Thus, the demand for catechins has increased considerably. Catechins have been extracted and isolated from tea leaves by numerous methods through several steps including: treatment of the tea leaves, extraction of catechins from teas into solvents, isolation of catechins from other extracted components, and drying the preparations to obtain catechin extracts in a powder form. This paper outlines the physical and chemical properties of the tea catechins and reviews the extraction steps of the various extraction methods, as a basis to improve and further develop the extraction and isolation of the tea catechins.     

Radiolysis of 1-naphthol in aqueous solutions

The effects of absorbed doses, initial pH and 1-naphthol concentration onto its radiolysis in aqueous sulphuric and hydrochloric acids by gamma rays from ⁶⁰Co were investigated. Under the experimental conditions, 1-naphthol degradation yields increased with increasing the absorbed doses (0.3–3.0 kGy) and with decreasing the initial 1-naphthol concentration (20–1 ppm). It was found out that the hydrated electrons did not play any significant roles in 1-naphthol radiolysis, as the degradation yields were higher at pH₀ ~ 0.46 compared to those at pH₀ ~ 2.0–5.0. The corresponding radiolytic yields G(−1-naphthol) were (6.13 ± 1.00)) × 10⁻² and (5.11 ± 0.22) × 10⁻² μmol/J in sulphuric acids, (15.61 ± 3.85) × 10⁻² and (4.76 ± 0.48) × 10⁻² μmol/J in hydrochloric acids. 1-Naphthol degradation rates could be described by the kinetic equations of pseudo-first-order reactions. An empirical relation between the observed reaction constants k _D and the initial 1-naphthol concentrations was established, enabling to predict the absorbed doses required for a given treatment efficiency. Three products of 1-naphthol degradation were revealed using an HPLC/UV procedure.     

Formation and characterization of a hydrophilic polymer hydrogel under gamma irradiation

Formation and characterization of hydrogel of a hydrophilic polymer in a wide range of gamma absorbed doses is reported. An aqueous solution contains 2% polyvinyl alcohol (PVA) by mass irradiated under gamma rays of ⁶⁰Co was chosen for study. The hydrogel was synthesized without using any additives. It was found that gel fraction is an exponential saturation function that increases with an increase of absorbed dose while swelling ratio is an exponential saturation function that decreases with an increase of absorbed dose. The results are described by energy transfer model.     

Designing an intelligent teaching simulator for learning to teach by practicing

Learning to teach is difficult for prospective teachers because of the complex nature of the work of teaching. Practicing (Lampert in J Teach Educ 61(1–2):21–34, 2010), interacting with the practice of teaching from a first-person perspective, may give them a unique experience in learning to teach. Computer-based simulators in which the apprentice teacher can interact with virtual students may be used to create that kind of experience. In this paper, we show how to apply techniques in artificial intelligence to design an intelligent learning environment. We show how to model the apprentice’s decision making and resources that can help him or her improve the practice of teaching.     

TEM characterization of chemically synthesized copper–gold nanoparticles

Dodecanethiol-capped Cu–Au nanoparticles, synthesized via a successive two-phase (water/toluene) and galvanic-exchange procedure, were characterized using transmission electron microscopy (TEM). The size range of the particles is around 1–7 nm. Electron-induced morphological evolution was observed under high resolution (HR) TEM. Cuboctahedral morphology was found to be thermodynamically stable. Electron-induced aggregation of two particles was also observed. Chemical ordering of cuboctahedral particles was studied by atomic-resolution high angle annular dark field (HAADF) imaging in scanning TEM (STEM) mode and energy dispersive X-ray (EDX) element mapping using a silicon drift detector (SDD). The particles were found to be Cu–Au mixed, and to be stable in air. Surface plasmon resonance (SPR), which is dependent on local structure and morphology, was investigated by electron energy loss spectroscopy (EELS).     

Determination of microelement distribution in different components of soil-plant systems

The leaves, stem, and roots of two types of shrubs (tea (Camellia sinensis) and sweet leaf (Sauropus androgynus)) and two types of herbs (vetiver grass (Vetiveria zizanioides L. Nash) and maize (Zea mays L)) and the Thucuc soil where the plants were growing were collected to be studied. The contents of 22 elements in the samples were determined by three methods: X-Ray fluorescence analysis (XRFA), gamma activation analysis (GAA), and the tracking method to study the distribution of these elements in plants and the soil-plant relationship. This study was carried out at the Flerov Laboratory of Nuclear Reactions (FLNR), Joint Institute for Nuclear Research (JINR), Dubna, Russia. The distribution of the elements in the soil-plant system was studied.     

Competition between Kondo and RKKY correlations in the presence of strong randomness

We propose that competition between Kondo and magnetic correlations results in a novel universality class for heavy fermion quantum criticality in the presence of strong randomness. Starting from an Anderson lattice model with disorder, we derive an effective local field theory in the dynamical mean-field theory approximation, where randomness is introduced into both hybridization and Ruderman-Kittel-Kasuya-Yosida (RKKY) interactions. Performing the saddle-point analysis in the U(1) slave-boson representation, we reveal its phase diagram which shows a quantum phase transition from a spin liquid state to a local Fermi liquid phase. In contrast with the clean limit case of the Anderson lattice model, the effective hybridization given by holon condensation turns out to vanish, resulting from the zero mean value of the hybridization coupling constant. However, we show that the holon density becomes finite when the variance of the hybridization is sufficiently larger than that of the RKKY coupling, giving rise to the Kondo effect. On the other hand, when the variance of the hybridization becomes smaller than that of the RKKY coupling, the Kondo effect disappears, resulting in a fully symmetric paramagnetic state, adiabatically connected to the spin liquid state of the disordered Heisenberg model. We investigate the quantum critical point beyond the mean-field approximation. Introducing quantum corrections fully self-consistently in the non-crossing approximation, we prove that the local charge susceptibility has exactly the same critical exponent as the local spin susceptibility, suggesting an enhanced symmetry at the local quantum critical point. This leads us to propose novel duality between the Kondo singlet phase and the critical local moment state beyond the Landau-Ginzburg-Wilson paradigm. The Landau-Ginzburg-Wilson forbidden duality serves the mechanism of electron fractionalization in critical impurity dynamics, where such fractionalized excitations are identified with topological excitations.     

A New Proof for the Convergence of an Individual Based Model to the Trait Substitution Sequence

We consider a continuous time stochastic individual based model for a population structured only by an inherited vector trait and with logistic interactions. We consider its limit in a context from adaptive dynamics: the population is large, the mutations are rare and the process is viewed in the timescale of mutations. Using averaging techniques due to Kurtz (in Lecture Notes in Control and Inform. Sci., vol. 177, pp. 186–209, 1992), we give a new proof of the convergence of the individual based model to the trait substitution sequence of Metz et al. (in Trends in Ecology and Evolution 7(6), 198–202, 1992), first worked out by Dieckman and Law (in Journal of Mathematical Biology 34(5–6), 579–612, 1996) and rigorously proved by Champagnat (in Theoretical Population Biology 69, 297–321, 2006): rigging the model such that “invasion implies substitution”, we obtain in the limit a process that jumps from one population equilibrium to another when mutations occur and invade the population.