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We compute all the tree-level contributions to the Wilson coefficients of the dimension-six Standard-Model effective theory in ultraviolet completions with general scalar, spinor and vector ...field content and arbitrary interactions. No assumption about the renormalizability of the high-energy theory is made. This provides a complete ultraviolet/infrared dictionary at the classical level, which can be used to study the low-energy implications of any model of interest, and also to look for explicit completions consistent with low-energy data.
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The invariance of physical observables under redefinitions of the quantum fields is a well-known and important property of quantum field theory. We study perturbative field redefinitions in ...effective theories, paying special attention to higher-order effects and their impact on matching to an ultraviolet theory at the classical and quantum levels.
Cross-linked oxalic acid/chitosan hydrogels (ChOxb) were synthesized, characterized and tested for the adsorption of azo-dyes (Reactive Red 195 RR195) in contaminated wastewater; this novel ...biodegradable material was highly efficient. SEM-EDS and N2 adsorption/desorption were used to analyze specific area; FTIR-ATR spectra evidenced electrostatic interactions between protonated amino groups of chitosan and oxalate ions (intensity decrease and shift of amide-II band). Adsorption performance in batch assays showed a maximum percentage of removal of 90.6%, at pH = 4 (initial dye concentration of 300 mg.L−1). The maximum adsorption capacity (Qm) at pH = 4 was 110.7 mg.g−1, positioning ChOxb as one of the most efficient adsorption materials. Oxalic acid (natural organic acid) is an eco-friendly cross-linking agent that reduced swelling and improved chemical stability of ChOxb at low pH = 2.5. Redlich-Peterson adsorption isotherm presented the best fit; adsorption thermodynamic parameters were evaluated. Mixed surface reaction and diffusion-controlled kinetic model was the equation that best fitted kinetic data. FTIR-ATR, SEM-EDS and Z-potential showed electrostatic interactions between dye and amino groups of ChOxb; ChOxd can be reused without losing adsorption capacity and competitive electrostatic interactions between ChOxb-nitrate were observed. This new bio-material is an excellent alternative for the removal of RR195, improving Qm with better structural and functional properties.
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•Oxalic acid cross-linked chitosan hydrogels were synthesized to remove Azo-dyes•Mixed surface reaction and diffusion-controlled kinetic model explained mechanisms•Redlich-Peterson model presented the best fit for the adsorption isotherm•Oxalic acid a natural organic dicarboxylic acid, is an ecofriendly crosslinker•Novel, biodegradable, eco-friendly and highly efficient material was characterized
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We study the impact of the leading non-renormalizable terms in the effective field theory that describes general extensions of the Standard Model with vector-like quarks that can decay into ...Standard Model particles. Dropping the usual assumption of renormalizability has several phenomenological consequences for the production and decay of the heavy quarks and also for Higgs physics. The most dramatic effects, including those associated with a long lifetime, occur for vector-like quarks with non-standard quantum numbers.
New information and communication technologies (ICTs) provide educators and learners with an innovative learning environment to stimulate and enhance the teaching and learning process. In this ...context, novel educational concepts such as blended learning are being developed. In the present paper, we present the results obtained from a blended learning experience carried out at the University of Granada. A total of 17 groups took part, with 1431 students registered for the 2009–2010 academic year. In this study, we use objective outcomes and the students’ perceptions regarding the blended learning activities performed. The study shows that the use of blended learning has a positive effect in reducing dropout rates and in improving exam marks. Moreover, the students’ perceptions on blended learning are interrelated, with their final marks depending on the blended learning activities, and on the students’ age, background and class attendance rate.
Copper(I) Cu2(μ-Br)2(tBuImCH2pyCH2L) n (L = OMe, NEt2, NHtBu) compounds supported by flexible functionalized NHC-based polydentate ligands have been prepared in a one-pot procedure by reacting the ...corresponding imidazolium salt with an excess of copper powder and Ag2O. An X-ray diffraction analysis has revealed that Cu2(μ-Br)2(tBuImCH2pyCH2NEt2) n is a linear coordination polymer formed by bimetallic Cu(μ-Br)2 units linked by the lutidine-based NHC-py-NEt2 ligand, which acts as a heteroditopic ligand with a 1κC-2κ2 N,N′ coordination mode. We propose that the polymeric compounds break down in the solution into more compact tetranuclear Cu2(μ-Br)2(tBuImCH2pyCH2L)2 compounds with a coordination mode identical to the functionalized NHC ligands. These compounds have been found to exhibit high catalytic activity in the Cu-catalyzed azide–alkyne cycloaddition (CuAAC) reaction. In particular, Cu2(μ-Br)2(tBuImCH2pyCH2NEt2)2 efficiently catalyzes the click reaction of a range of azides and alkynes, under an inert atmosphere at room temperature in neat conditions at a very low catalyst loading, to quantitatively afford the corresponding 1,4-disubstituted 1,2,3-triazole derivatives in a few minutes. The cycloaddition reaction of benzyl azide to phenylacetylene can be performed at 25–50 ppm catalyst loading by increasing the reaction time and/or temperature. Reactivity studies have shown that the activation of the polynuclear catalyst precursor involves the alkyne deprotonation by the NHC moiety of the polydentate ligand to afford a copper(I)-alkynyl species bearing a functionalized imidazolium ligand. DFT calculations support the participation of the dinuclear species (CuBr)2(μ-tBuImCH2pyCH2NEt2), resulting from the fragmentation of the tetranuclear compound, as the catalytically active species. The proposed reaction pathway proceeds through zwitterionic dinuclear intermediates and entails the active participation of both copper atoms, as well as the NHC moiety as an internal base, which activates the reacting alkyne via deprotonation.
We study the Lorentz and Dirac algebra, including the antisymmetric ϵ tensor and the γ5 matrix, in implicit gauge-invariant regularization/renormalization methods defined in fixed integer dimensions. ...They include constrained differential, implicit and four-dimensional renormalization. We find that these fixed-dimension methods face the same difficulties as the different versions of dimensional regularization. We propose a consistent procedure in these methods, similar to the consistent version of regularization by dimensional reduction.
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We classify all possible new scalar particles that can have renormalizable linear couplings to Standard Model fields and therefore be singly produced at colliders. We show that this ...classification exhausts the list of heavy scalar particles that contribute at the tree level to the Standard Model effective Lagrangian to dimension six. We compute this effective Lagrangian for a general scenario with an arbitrary number of new scalar particles and obtain flavor-preserving constraints on their couplings and masses. This completes the tree-level matching of the coefficients of dimension five and six operators in the effective Lagrangian to arbitrary extensions of the Standard Model.
We study extensions of the Standard Model with general new vector bosons. The full Standard Model gauge symmetry is used to classify the extra vectors and constrain their couplings. We derive the ...corresponding effective Lagrangian, valid at energies lower than the mass of the extra vectors, and use it to extract limits from electroweak precision observables, including LEP 2 data. We consider both universal and nonuniversal couplings to fermions. We study the interplay of several extra vectors, which can have the effect of opening new regions in parameter space. In particular, it allows to explain the anomaly in the bottom forward-backward asymmetry with perturbative couplings. Finally, we analyze quantitatively the implications for the Higgs mass.
The borrowing hydrogen methodology allows for the use of alcohols as alkylating agents for CC bond forming processes offering significant environmental benefits over traditional approaches. ...Iridium(I)‐cyclooctadiene complexes having a NHC ligand with a O‐ or N‐functionalised wingtip efficiently catalysed the oxidation and β‐alkylation of secondary alcohols with primary alcohols in the presence of a base. The cationic complex Ir(NCCH3)(cod)(MeIm(2‐ methoxybenzyl))BF4 (cod=1,5‐cyclooctadiene, MeIm=1‐methylimidazolyl) having a rigid O‐functionalised wingtip, shows the best catalyst performance in the dehydrogenation of benzyl alcohol in acetone, with an initial turnover frequency (TOF0) of 1283 h−1, and also in the β‐alkylation of 2‐propanol with butan‐1‐ol, which gives a conversion of 94 % in 10 h with a selectivity of 99 % for heptan‐2‐ol. We have investigated the full reaction mechanism including the dehydrogenation, the cross‐aldol condensation and the hydrogenation step by DFT calculations. Interestingly, these studies revealed the participation of the iridium catalyst in the key step leading to the formation of the new CC bond that involves the reaction of an O‐bound enolate generated in the basic medium with the electrophilic aldehyde.
An active role: Iridium(I)‐cyclooctadiene complexes having an O/N‐functionalised N‐heterocyclic carbene (NHC) ligand efficiently catalysed the oxidation and β‐alkylation of secondary alcohols with primary alcohols. DFT calculations on the full reaction mechanism, including the dehydrogenation, the cross‐condensation and the hydrogenation step, revealed active participation of the iridium catalyst in the key step, leading to the formation of the new CC bond.
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