On semidirectly closed pseudovarieties of aperiodic semigroups

The aim of this work is to study the unknown intervals of the lattice of aperiodic pseudovarieties which are semidirectly closed and answer questions proposed by Almeida in his book “Finite Semigroups and Universal Algebra”. The main results state that the intervals [V^*(B₂),ER∩LR] and [V^*(B₂¹),ER∩A] are not trivial, and that both contain a chain isomorphic to the chain of real numbers. These results are a consequence of the study of the semidirectly closed pseudovariety generated by the aperiodic Brandt semigroup B₂.     

A logic of implications in algebra and coalgebra

Implications in a category can be presented as epimorphisms: an object satisfies the implication iff it is injective with respect to that epimorphism. G. Ro?u formulated a logic for deriving an implication from other implications. We present two versions of implicational logics: a general one and a finitary one (for epimorphisms with finitely presentable domains and codomains). In categories Alg Σ of algebras on a given signature our logic specializes to the implicational logic of R. Quackenbush. In categories Coalg H of coalgebras for a given accessible endofunctor H of sets we derive a logic for implications in the sense of P. Gumm.     

Methiocarb Degradation by Electro-Fenton: Ecotoxicological Evaluation

This paper studies the degradation of methiocarb, a highly hazardous pesticide found in waters and wastewaters, through an electro-Fenton process, using a boron-doped diamond anode and a carbon felt cathode; and evaluates its potential to reduce toxicity towards the model organism Daphnia magna. The influence of applied current density and type and concentration of added iron source, Fe₂(SO₄)₃·5H₂O or FeCl₃·6H₂O, is assessed in the degradation experiments of methiocarb aqueous solutions. The experimental results show that electro-Fenton can be successfully used to degrade methiocarb and to reduce its high toxicity towards D. magna. Total methiocarb removal is achieved at the applied electric charge of 90 C, and a 450× reduction in the acute toxicity towards D. magna, on average, from approximately 900 toxic units to 2 toxic units, is observed at the end of the experiments. No significant differences are found between the two iron sources studied. At the lowest applied anodic current density, 12.5 A m⁻², an increase in iron concentration led to lower methiocarb removal rates, but the opposite is found at the highest applied current densities. The highest organic carbon removal is obtained at the lowest applied current density and added iron concentration.     

Novel efficient synthesis of 3,4-dihydro-6-substituted-3-phenylpyrimidin-2(1H)-ones

A new attractive and convenient strategy for the synthesis of 3,4-dihydro-6-substituted-3-phenylpyrimidin-2(1H)-ones is described. Photolysis (λ = 254 nm) of 4-allyl-tetrazolones in alcoholic solutions produces the corresponding pyrimidinones as the sole product in nearly quantitative yields, with simultaneous extrusion of molecular nitrogen. Work-up procedures consist in the simple evaporation of the solvent under reduced pressure, in mild conditions. Heats of reaction for the photocleavage process of 4-allyltetrazolones were calculated, indicating high stability of the resulting products.     

Optimal cycle for a signalized intersection using Global Optimization and Complementarity

A queueing system resulting from a signalised intersection regulated by pre-timed control in an urban traffic network is considered in this paper. Subsequently, we analyse the manner in which Global Optimisation and Complementarity may be used to determine the optimal cycle length and green split allocation for an isolated signalised intersection. The model in question has been formulated as a Mathematical Program with Equilibrium (or Complementarity) Constraints (MPEC). A?sequential complementarity algorithm for computing a global minimum for the MPEC is also subject to analysis in this paper. Furthermore, computational experience is included to demonstrate the efficiency of this method as an effective solution for the problem in question.     

Analysis of the basis set and correlation effects on the computation of molecular polarizabilities using molecular polarization maps

In the present report, we analyze the effect of augmenting the basis set and the level of the theory in the computation of the molecular polarization potential and it is used as a tool to understand their spatial effects in the calculation of molecular polarizabilities. This is analyzed in the present report through the results obtained for three reference molecules: hydrogen cyanide, formaldehyde and urea. Accordingly, different basis sets were used for the calculations, including: 6-31G(D), 6-31G(D,P), 6-31G(2D,2P) and 6-31++G(2D,2P). On the other hand, calculations at different levels of the theory were considered, including: Hartree–Fock, Moller–Plesset second order (MP2) and fourth order (MP4) as well as the functionals BLYP and B3LYP at the density functional theory. The results of the polarization maps reveal similar trends observed with the calculation of the different components of the polarizability tensor. However, the use of the maps permits to understand spatial effects specific for each level of calculation and each basis set.     

Sigmatropic rearrangements in 5-allyloxytetrazoles

Mechanisms of thermal isomerization of allyl tetrazolyl ethers derived from the carbocyclic allylic alcohols cyclohex-2-enol and 3-methylcyclohex-2-enol and from the natural terpene alcohol nerol were investigated. In the process of the syntheses of the three 1-aryl-5-allyloxytetrazoles, their rapid isomerization to the corresponding 1-aryl-4-allyltetrazol-5-ones occurred. The experiments showed that the imidates rearrange exclusively through a [3,3']-sigmatropic migration of the allylic system from O to N, with inversion. Mechanistic proposals are based on product analysis and extensive quantum chemical calculations at the DFT(B3LYP) and MP2 levels, on O-allyl and N-allyl isomers and on putative transition state structures for [1,3']- and [3,3']-sigmatropic migrations. The experimental observations could be only explained on the basis of the MP2/6-31G(d,p) calculations that favoured the [3,3']-sigmatropic migrations, yielding lower energies both for the transition states and for the final isomerization products.     

Vibrational spectra and structure of 1-phenyltetrazole and 5-chloro-1-phenyltetrazole: A combined study by low temperature matrix isolation and solid state FTIR spectroscopy and DFT calculations

Infrared spectra of 1-phenyltetrazole (C₇N₄H₆) and 5-chloro-1-phenyltetrazole (C₇N₄H₅Cl) isolated in argon matrixes (T=8 K) and in the solid state (at room temperature) were studied. DFT(B3LYP)/6-31G* calculations predict the minimum energy conformation of 1-phenyltetrazole as being non-planar, with the two rings (phenyl and tetrazole) twisted by 29°. For 5-chloro-1-phenyltetrazole, the optimized dihedral angle between the two rings is larger (48°). The theoretically calculated IR spectra of both compounds fit well the spectra observed experimentally. This allowed a reliable assignment of observed IR absorption bands.