PEO-[M(CN)5NO](x-) (M = Fe, Mn, or Cr) interaction as a driving force in the partitioning of the pentacyanonitrosylmetallate anion in ATPS: strong effect of the central atom

The partitioning behavior of pentacyanonitrosilmetallate complexes[Fe(CN) 5NO] (2-), [Mn(CN) 5NO] (3-), and [Cr(CN) 5NO] (3-)has been studied in aqueous two-phase systems (ATPS) formed by adding poly(ethylene oxide) (PEO; 4000 g mol (-1)) to an aqueous salt solution (Li 2SO 4, Na 2SO 4, CuSO 4, or ZnSO 4). The complexes partition coefficients ( K complex) in each of these ATPS have been determined as a function of increasing tie-line length (TLL) and temperature. Unlike the partition behavior of most ions, [Fe(CN) 5NO] (2-) and [Mn(CN) 5NO] (3-) anions are concentrated in the polymer-rich phase with K values depending on the nature of the central atom as follows: K [ F e ( C N ) 5 N O ] 2 - > K [ M n ( C N ) 5 N O ] 3 - > K [ C r ( C N ) 5 N O ] 3 - . The effect of ATPS salts in the complex partitioning behavior has also been verified following the order Li 2SO 4 > Na 2SO 4 > ZnSO 4. Thermodynamic analysis revealed that the presence of anions in the polymer-rich phase is caused by an EO-[M(CN) 5NO] ( x- ) (M = Fe, Mn, or Cr) enthalpic interaction. However, when this enthalpic interaction is weak, as in the case of the [Cr(CN) 5NO] (3-) anion ( K [ C r ( C N ) 5 N O ] 3 - < 1), entropic driving forces dominate the transfer process, then causing the anions to concentrate in the salt-rich phase.     

Sur quelques récents résultats dans la théorie des surfaces algébriques

Sans résumé     

On the variable order dynamics of the nonlinear wake caused by a sedimenting particle

In this work we develop a variable order (VO) differential equation of motion for a spherical particle sedimenting in a quiescent viscous liquid. In particular, we examine the various force terms in the equation of motion and propose a new form for the history drag acting on the particle. We show that the variable order formulation allows for an effective way to express the dynamic transition of the dominant forces over the entire time of the motion of the particle from rest to terminal velocity. The use of VO operators also allows us to examine the evolving dynamics of the wake during sedimentation. Using numerical data from a finite element simulation of a sedimenting particle, we first solve for the order of the derivative that returns the correct decay of the history force. We then propose a relatively simple expression for the history force that is a function of the Reynolds number and particle-to-fluid density ratio. The new history drag expression correlates very well (R²>0.99) with the numerical data for terminal Reynolds numbers ranging from 2.5 to 20, and for particle-to-fluid density ratios of interest in practice (1<β<10).     

Effect of High Pressure Treatments on protease and β-Galactosidase Activities of Table Olives

In this work the effect of high pressure treatments (50 and 110 MPa for 15 and 30 min.) on protease and g -galactosidase activities of mature table olives (Portuguese Douro variety) was studied. The influence of the applied treatments was quantified for the soluble and the ionically and covalently bound to cell wall fractions for both enzymes. For g -galactosidase the treatments caused no significant changes in activity, while proteolytic activity was reduced by more than 90% in all cases. For proteolytic activity significantly different baric stabilities were also found for the three fractions studied.     

Application of a macromolecular micellar system formed by the P123 triblock copolymer for determination of copper concentrations

This work proposes a method for determination Cu(II) concentrations, based on the formation of a copper-1-nitroso-2-naphthol complex, in the presence of micelles; formed by a triblock copolymer, made up of two blocks of polyethylene oxide (PEO), and one block of polypropylene oxide (PPO). The insoluble copper complexes, are concentrated inside the hydrophobic micelle core; formed by the PPO block. For a solution containing 0.200 mg L⁻¹ Cu(II), the proposed method had a relative standard deviation of 2.0% (n = 3); an absolute error from 0.11 to 0.39 mg L⁻¹; and a linear calibration range, from 0.200 to 0.800 mg L⁻¹. Detection and quantification limits, were 43.1 mg L⁻¹ and 144 mg L⁻¹, respectively. We show that there is excellent agreement, between the results obtained using our novel method; and those obtained using flame atomic absorption spectrometry: In the determination of Cu(II) concentrations, in Brazilian sugar-cane spirits. The proposed method, is the first to apply macromolecular micelle systems, to the determination of copper concentrations; and improves upon the results obtained using molecular surfactants. This method is environmentally friendly (since it does not use any organic solvents for extraction), and the triblock copolymer is biodegradable and non-toxic.      

Synthèse de l'oxo-7 7H cyclohepta[b] pyridine et de quelques dérivés

This communication describes the synthesis of 7-one (7H) cyclohepta[b]pyridine and some derivatives (6,8-dimethyl; 8-methyl; 8-ethyl….). These compounds have been obtained by condensation of ketones with 2,3-diformylpyridine.