DFT calculation of the chromyl nitrate, CrO2(NO3)2 The molecular force field

We have carried out a structural and vibrational theoretical study for chromyl nitrate. The density functional theory has been used to study its structure and vibrational properties. The geometries were fully optimised at the B3LYP/Lanl2DZ, B3LYP/6-31G* and B3LYP/6-311++G levels of theory and the harmonic vibrational frequencies were evaluated at the same levels. The calculated harmonic vibrational frequencies for chromyl nitrate are consistent with the experimental IR and Raman spectra in the solid and liquid phases. These calculations gave us a precise knowledge of the normal modes of vibration taking into account the type of coordination adopted by nitrate groups of this compound as monodentate and bidentate. We have also made the assignment of all the observed bands in the vibrational spectra for chromyl nitrate. The nature of the Cr-O and Cr<--O bonds in the compound were quantitatively investigated by means of Natural Bond Order (NBO) analysis. The topological properties of electronic charge density are analysed employing Bader's Atoms in Molecules theory (AIM).     

Ultrasound-assisted dynamic extraction of valuable compounds from aromatic plants and flowers as compared with steam distillation and superheated liquid extraction

A method for the extraction of valuable compounds from plants and flowers (viz. laurel, rosemary, thyme, oregano and tuberose) is proposed. The dynamic approach allows go-and-backward circulation of the extractant (ethanol) through the solid sample subjected to the action of an ultrasound probe (thus reducing sample amount and avoiding overpressure). A multivariate optimisation study and application of the optimum values of the variables to kinetics studies show that 10 min is sufficient to obtain extraction efficiencies that greatly surpass those provided by steam distillation for essential oils or superheated liquid extraction for these oils and other valuable compounds, with lower costs and higher quality of the extract. The extraction time of the proposed method is 176–165 min shorter than steam distillation and 31–20 min shorter than superheated liquid extraction, depending on the target compound.     

Measure partitions using hyperplanes with fixed directions

We study nested partitions of R^d obtained by successive cuts using hyperplanes with fixed directions. We establish the number of measures that can be split evenly simultaneously by taking a partition of this kind and then distributing the parts among k sets. This generalises classical necklace splitting results and their more recent high-dimensional versions. With similar methods we show that in the plane, for any t measures there is a path formed only by horizontal and vertical segments using at most t - 1 turns that splits them by half simultaneously, and optimal masspartitioning results for chessboard colourings of R^d using hyperplanes with fixed directions.     

Simple and efficient heterogeneous copper catalysts for enantioselective C-H carbene insertion

Immobilized box-Cu complexes are able to efficiently catalyze the insertion of a carbene, from methyl phenyldiazoacetate, into C-H bonds of THF, with high enantioselectivity (up to 88% ee). The immobilization not only allows recovery and reuse of the enantioselective catalyst but also provides an improvement in the selectivities from the values obtained in solution, probably due to a confinement effect of the bidimensional support. [reaction: see text].     

A characteristic property of the Euclidean disc

In this paper the following is proved: Let K ⊂ $ \mathbb{E}^2 $ \mathbb{E}^2 be a smooth strictly convex body, and let L ⊂ $ \mathbb{E}^2 $ \mathbb{E}^2 be a line. Assume that for every point x ∈ L/K the two tangent segments from x to K have the same length, and the line joining the two contact points passes through a fixed point in the plane. Then K is an Euclidean disc.     

Prediction and Conditional Simulation of a 2D Lognormal Diffusion Random Field

This paper describes techniques for estimation, prediction and conditional simulation of two-parameter lognormal diffusion random fields which are diffusions on each coordinate and satisfy a particular Markov property. The estimates of the drift and diffusion coefficients, which characterize the lognormal diffusion random field under certain conditions, are used for obtaining kriging predictors. The conditional simulations are obtained using the estimates of the drift and diffusion coefficients, kriging prediction and unconditional simulation for the lognormal diffusion random field.      

Sensitive fluorescent chemosensor for Hg(II) in aqueous solution using 4’-dimethylaminochalcone

Journal of Fluorescence - Mercury (Hg) is an element with high toxicity, especially to the nervous system, and fluorescent pigments are used to visualize dynamic processes in living cells. A little...     

On a conjecture of Grünbaum concerning partitions of convex sets

In this paper the following is proved: let K ∈ ℝ² be a convex body and t ∈ [0, 1/4]. If the diameter of K is at least √37 times the minimum width, then there is a pair of orthogonal lines that partition K into four pieces of areas t, t, (1/2−t), (1/2−t) in clockwise order. Furthermore, if K is centrally symmetric, then we can replace the factor √37 by 3.     

Experimental characterization of domain walls dynamics in a photorefractive oscillator

We report on the experimental characterization of domain wall dynamics in a photorefractive resonator in a degenerate four-wave mixing configuration. We show how the non-flat profile of the emitted field affects the velocity of domain walls as well as the variations of intensity and phase gradient during their motion. We find a clear correlation between these two last quantities that allows the experimental determination of the chirality that governs the domain walls’ dynamics. PACS 42.65.Sf; 47.54.+r; 42.65.Hw     

Non-Associativity in the Clifford Bundle on the Parallelizable Torsion 7-Sphere

In this paper we discuss generalized properties of non-associativity in Clifford bundles on the 7-sphere S ⁷. Novel and prominent properties inherited from the non-associative structure of the Clifford bundle on S ⁷ are demonstrated. They naturally lead to general transformations of the spinor fields on S ⁷ and have dramatic consequences for the associated Ka?-Moody current algebras. All additional properties concerning the non-associative structure in the Clifford bundle on S ⁷ are considered. We further discuss and explore their applications.