From microscopic insights of H2 adsorption to uptake estimations in MOFs

The adsorption of hydrogen in MOFs takes place mainly close to the inorganic secondary building unit (IBU). The adsorption capacities on MIL-88, UiO-66, MIL-47 and MFU-1 were investigated. Quantum chemical calculations at the ab initio HF/MP2 theoretical level were employed to estimate the maximum uptake of H(2) molecules per metallic centre. Extrapolating the results on small clusters to the unit cell of each particular MOF, the H(2) uptakes (gravimetric and volumetric) were estimated. The loading of hydrogen per metal atom (H(2) molecules/M-atom) and the density of metal atoms (M-atoms ?(-3)) were defined as useful parameters to assess hydrogen storage properties and to estimate the optimum density that the material should have to be a good H(2) adsorbent. It was found that values above 3 H(2) molecules/M-atom and around 0.004 M-atoms ?(-3) for MOFs with densities around 0.7-1.0 g cm(-3) are required to reach the 2015 storage targets.     

Trace level vanadium determination using thermal lens spectrophotometry

Trace level vanadium determination is reported using a dual beam thermal lens spectrometer. The thermal lens was generated using an argon ion beam laser (pump beam) which was focused into a sample cuvette. The thermal lens signal (TLs) was monitored with a He-Ne laser beam and a photodiode detector. Multichannel averager software was developed for processing the transient TLs. The optimal set up, ensuring maximum sensitivity and linear calibration graphs was obtained using experimental design techniques. Under optimized conditions, the detection limits for aqueous and ethanol-water (2+3 v/v) and (4+1 v/v) vanadium complex solutions were, respectively, 0.0071 mg/l, 0.0065 and 0.0039 mg/l.     

Determination of the enantiomeric excess of α-hydroxy acids

This work describes a convenient and accurate method for optical purity determination of α-hydroxy acids. Their derivatization with commercially available valine methyl ester affords diastereoisomers easily separable by HPLC using achiral C₁₈ columns.     

Liouvillian first integrals for the planar Lotka-Volterra system

We complete the classication of all Lotka-Volterra systemsx=x(ax+by+c),y=y(Ax+By+C), having a Liouvillian first integral. In our classification we take into account the first integrals coming from the existence of exponential factors.     

Flow-injection spectrofluorimetric determination of paracetamol

A flow-injection spectrofluorimetric determination of paracetamol is reported, based on the oxidation of the analyte with potassium hexacyanoferrate(III) immobilized on an anion-exchange resin, the fluorescence being enhanced with N,N′-dimethylformamide. Concentrations of paracetamol in the range 0.04–17.60 mg l^?1 are determined with a relative standard deviation of 1.5%. The injection rate is 25 samples h^?1. The influence of foreign species and the determination of paracetamol in several pharamaceutical formulations are also reported.     

The problem of distinguishing between a center and a focus for nilpotent and degenerate analytic systems

In this work we study the centers of planar analytic vector fields which are limit of linear type centers. It is proved that all the nilpotent centers are limit of linear type centers and consequently the Poincaré-Liapunov method to find linear type centers can be also used to find the nilpotent centers. Moreover, we show that the degenerate centers which are limit of linear type centers are also detectable with the Poincaré-Liapunov method.     

Synthesis and some chemical transformations of 3-ferrocenyl-3-phenylcyclopropene

Crystalline 3-ferrocenyl-3-phenylcyclopropene was obtained by dehydrobromination of 2-bromo-l-ferrocenyl-l-phenylcyclopropane with potassiumtert-butoxide in dimethyl sulfoxide. The compound synthesized undergoes catalytic hydrogenation to l-ferrocenyl-I-phenylcyclopropane, reacts with 1,3-diphenylisobenzofuran to give the expected product of stereospecific [4+2[-cycloaddition and 3-ferrocenylindene, and also undegoes opening of the small ring on treatment with superacids to give 3-ferrocenylindene as the major product. The data of single crystal X-ray diffraction analysis of 1-ferrocenyl-l-phenylcyclopropane and the diene adduct of 3-ferrocenyl-3-phenylcyclopropene with 1,3-diphenylisobenzofuran are given.     

Pavelka-style completeness in expansions of Łukasiewicz logic

An algebraic setting for the validity of Pavelka style completeness for some natural expansions of Łukasiewicz logic by new connectives and rational constants is given. This algebraic approach is based on the fact that the standard MV-algebra on the real segment [0, 1] is an injective MV-algebra. In particular the logics associated with MV-algebras with product and with divisible MV-algebras are considered. The author express his gratitude to Roberto Cignoli, for his advice during the preparation of this paper.