Local real analysis in locally homogeneous spaces

We introduce the concept of locally homogeneous space, and prove in this context L ^p and C ^α estimates for singular and fractional integrals, as well as L ^p estimates on the commutator of a singular or fractional integral with a BMO or VMO function. These results are motivated by local a priori estimates for subelliptic equations.     

Determination of thiolic compounds as mercury complexes by cold vapor atomic absorption spectrometry and its application to wines

We report on the application of a commercially available mercury analyzer, which is based on vapour generation of Hg(0) by NaBH(4) reduction and atomic absorption detection, to the quantification and characterization of -SH groups and its application to wine samples. The behaviour of Hg(II) and thiol-Hg(II) (RS-Hg) complexes at nanomolar level (RS=l-cysteine, dl-penicillamine, N-acetyl penicillamine, glutathione, cysteinylglycine, homocysteine) has been studied following their reduction with alkaline NaBH(4) to give Hg(0). In the absence of thiol-Hg(II) is quantitatively converted to Hg(0) by stoichiometric amount of NaBH(4) (reaction ratio 1/4mole NaBH(4)/mole Hg), while the complete reduction of Hg(II)-thiol complexes to Hg(0) requires molar excess of NaBH(4) up to six orders of magnitude, depending on the type of complex and on the pK(a) of the thiolic group. Under an appropriate excess of reductant, Hg(II) and its thiol complexes are not distinguishable giving the same response. These properties allow the discrimination of Hg(II) from Hg(II)-thiol complexes without any preliminary separation and the quantification of thiol groups. Instrumental detection limits are as low as 2.5pg, permitting sample dilution, therefore, minimizing the risk of possible interferences occurring with complex real matrices. The method has been applied to quantification of thiol groups in wine samples. Comparison with results obtained by HPLC coupled to atomic fluorescence detection confirmed the promising potentialities of the method.     

Selective NO(x) optical sensing with surface-confined osmium polypyridyl complexes

Optical detection of parts-per-million (ppm) levels of NO2 (1-10 ppm) and NO(x) (800-2550 ppm) by a structurally well-defined monolayer consisting of osmium polypyridyl complexes on glass substrates has been demonstrated.     

Hierarchical structured tungsten oxide nanocrystals via hydrothermal route: microstructure, formation mechanism and humidity sensing

Hierarchical structured tungsten oxide nanocrystals were synthesized via the hydrothermal route assisted by a capping agent of ammonium benzoate (AB). The products were characterized using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The experimental results show that the crystal microstructures could be changed from flower-shape to star-shape by changing the mole ratio of ammonium benzoate to sodium tungstate (AB/ST). The crystal phases were changed from orthorhombic WO₃?0.33H₂O to hexagonal WO₃ with the increase in the concentration of AB. Based on the results from Fourier transform infrared spectroscopy and time-dependent growth analysis, a self-assembly growth mechanism has been proposed for the formation of flower, spherical, and star-netted microstructures at different mole ratios of the AB/ST. The star-netted WO₃ nanocrystals were applied as a sensitive layer for humidity sensing performed using a Love-mode ZnO/36^° Y-cut LiTaO₃ surface acoustic wave device, and a stable and sensitive response to the change of relative humidity was obtained.     

Dynamics of benzene guest inside a self-assembled cylindrical capsule: a combined solid-state 2H NMR and molecular dynamics simulation study

The reorientational dynamics of benzene-d(6) molecules hosted into the cavity of a cavitand-based, self-assembled capsule was investigated by Molecular Dynamics (MD) simulations and temperature-dependent solid-state (2)H NMR spectroscopy. MD simulations were preliminarily performed to assess the motional models of the guest molecules inside the capsules. An in-plane fast reorientation of the benzene guest around the C(6) symmetry axis (B1 motion), characterized by correlation times of the order of picoseconds, was predicted with an activation barrier ( approximately 8 kJ/mol) very similar to that found for neat benzene in the liquid state. An out-of-plane reorientation corresponding to a nutation of the C(6) symmetry axis in a cone angle of 39 degrees (B2 motion, 373 K) with an activation barrier ( approximately 39 kJ/mol) definitely larger than that of liquid benzene was also anticipated. In the temperature range 293-373 K correlation times of the order of a nanosecond have been calculated and a transition from fast to slow regime in the (2)H NMR scale has been predicted between 293 and 173 K. (2)H NMR spectroscopic analysis, carried out in the temperature range 173-373 K on the solid capsules containing the perdeuterated guest (two benzene molecules/capsule), confirmed the occurrence of the B1 and B2 motions found in slow exchange in the (2)H NMR time scale. Line shape simulation of the (2)H NMR spectral lines permitted defining a cone angle value of 39 degrees at 373 K and 35 degrees at 173 K for the nutation axis. The T(1) values measured for the (2)H nuclei of the encapsulated aromatic guest gave correlation times and energetic barrier for the in-plane motion B1 in fine agreement with theoretical calculation. The experimental correlation time for B2 as well as the corresponding energetic barrier are in the same range found for B1. A molecular mechanism for the encapsulated guest accounting for the B1 and B2 motions was also provided.     

Properties of uncharged water-soluble tetra(ω-methoxypolyethyleneoxy)phthalocyanine free base: Viable switching of the optical response by means of H3O+ ions

An uncharged water-soluble tetra (ω-methoxypolyethyleneoxy)phthalocyanine was characterized by MALDI-TOF mass spectrometry, UV–vis and luminescence measurements. The polyether substituents render water soluble this uncharged phthalocyanine. Relevant changes are observed in emission measurements upon protonation. The phthalocyanine free base and its protonated forms can be switched alternating H₃O⁺ and OH^? ions as inputs, being the intensity of the luminescence spectra the output. Binary codes 1 or 0 can be assigned to the high luminescent phthalocyanine free base state or to the low luminescent protonated state, respectively. The read-out procedure is fast and the system is reversible. In addition, the exploiting of the luminescent properties of the present water soluble phthalocyanine could be of relevance also for biological applications (photosensitizers for the photodynamic therapy).