CO2 Adsorption Investigation on an Innovative Nanocomposite Material with Hierarchical Porosity.

A NaX nanozeolite-geopolymer monolith, with hierarchical porosity, has been produced by a one-pot hydrothermal synthesis using metakaolin as alluminosilicate source and a sodium silicate solution as activator. Its final composition, reported in terms of oxides, is 1.3-Na2O-3.0SiO2-1Al2O3-12H2O. Its microstructural and chemical features and CO2 adsorption performance have been investigated. The microstructure of the composite is characterized by NaX zeolite nanocrystals glued by the geopolymeric binder to form a complex three-dimensional network of pores. Overall porosity resulted ~23.5%, whereas compressive strength is 16±0.7 MPa. Monolith showed BET surface area of 350 m²/g, a micropore surface area of 280 m²/g and a mesopore volume, due to the geopolymeric binder, of 0.09 cm³/g. Its CO2 adsorption capacity has been measured at the temperatures of 7, 25 and 42 °C up to 15 bar using an optimized Sievert-type (volumetric) apparatus. All the adsorption data were evaluated by Toth/Langmuir isotherm model and commercial pure NaX zeolite was used as reference. CO2 adsorption isotherms show a maximum uptake value around 21 wt% at (~7 °C) that decrease to 18 wt% at high temperature (~42 °C) passing through 19 wt% at room temperature (~25 °C). The homogeneity grade of the surface, as obtained using Toth analysis performed on the adsorption isotherm, is close to t ≅ 0.40, lower than the 0.61 obtained for pure commercial NaX zeolite, as a consequence of the binder formation. Monolith exhibits a notably higher K values and quicker saturation with respect to reference that can be ascribed to the presence of mesoporosity that provides an easier and faster transport of CO2 in the NaX nanozeolite framework. The produced composite is a potential solid adsorbent candidate in industrial process.

Effect of L-carnitine on the reactive hyperemia in patients affected by peripheral vascular disease: a double-blind, crossover study.

A double-blind, crossover study was designed to evaluate the effect of L-carnitine on the reactive hyperemia in patients with peripheral vascular disease. After drug washout, 18 patients were randomly assigned to receive placebo or L-carnitine, 3 g IV as a bolus, followed by continuous intravenous infusion of 2 mg/kg/min for thirty minutes. Blood flow in the affected limb was measured by impedance plethysmography, under resting conditions and every two minutes for ten minutes after a five-minute ischemia induced in the affected limb. As compared with placebo, L-carnitine did not modify blood flow at rest. On the contrary, the hyperemic response with carnitine was higher than that observed with placebo. A significant increase in blood flow was found two, four, and six minutes after the release of ischemia with placebo, whereas the blood perfusion to the affected limb rose significantly at all times of recording after carnitine administration. Moreover, the values of the blood flow at two and ten minutes with carnitine were significantly higher than those recorded after placebo at the same times of recording. After the release of ischemia, the mean maximum value of blood flow observed after carnitine was 3.1 +/- 1.4 mL/min/100 mL, a value significantly higher than that recorded after placebo, which was 2.7 +/- 1.3 mL/min/100 mL (p less than 0.05). In conclusion, this study demonstrates that L-carnitine, although not affecting blood flow and ankle/arm systolic blood pressure ratio under resting conditions, improves the functional circulatory reserve in patients with peripheral vascular disease.

Beneficial effect of a new prostacyclin derivative on the walking capacity in patients with peripheral arterial insufficiency.

The efficacy, tolerance and safety of iloprost, a stable analogue of carbaprostacyclin, were evaluated in 7 patients with peripheral arterial insufficiency at stage II of Fontaine's classification. After washout, placebo was infused intravenously for seven days, then iloprost was given by a six-hour intravenous infusion of 1 ng/kg/min over the next seven days. At the end of each period, the initial (ICD) and the absolute (ACD) claudication distance were measured by treadmill. The ankle/arm systolic blood pressure ratio (WI) was also assessed, at rest and ten minutes after exercise. As compared with placebo, ICD increased from 98 +/- 60 to 137 +/- 91 meters (p less than 0.05) and ACD from 151 +/- 76 to 210 +/- 95 meters (p less than 0.05). Similarly, WI rose from 0.44 +/- 0.14 to 0.52 +/- 0.18 (p less than 0.05) at rest and from 0.40 +/- 0.13 to 0.48 +/- 0.20 (p less than 0.05) ten minutes after treadmill exercise. Owing to the spontaneous fluctuation in walking distance experienced by such patients, an increase in ACD greater than or equal to 50% was considered as clinically relevant. In 3 patients, who experienced such an improvement, iloprost continued to be infused at the same dosage as before, for an additional seven days. In the remaining 4 patients (nonresponders), the dose was increased to 2 ng/kg/min.(ABSTRACT TRUNCATED AT 250 WORDS)

Electronic structure of cluster assembled nanostructured TiO(2) by resonant photoemission at the Ti L(2,3) edge.

The electronic structure of cluster assembled nanostructured TiO(2) thin films has been investigated by resonant photoemission experiments with photon energies across the Ti L(2,3) edge. The samples were produced by supersonic cluster beam deposition with a pulsed microplasma cluster source. The valence band shows resonance enhancements in the binding energy region between 4 and 8 eV, populated by O 2p and hybridized Ti 3d states, and in the region about 1 eV below the Fermi level associated with defects related Ti 3d states. The data show that in as-deposited films Ti atoms are mainly fully (sixfolds) coordinated to oxygen atoms in octahedral symmetry and only a small fraction is in a broken symmetry environment. Since resonant photoemission is closely linked to the local electronic and structural configurations around the Ti atom, it is possible to correlate the resonant photoemission intensity and lineshape with the presence of defects of the films and with the degree of hybridization between the titanium and oxygen atoms.

Increases in walking distance in patients with peripheral vascular disease treated with L-carnitine: a double-blind, cross-over study.

A double-blind, cross-over study was designed to evaluate the effects of L-carnitine in patients with peripheral vascular disease. After drug washout, 20 patients were randomly assigned to receive placebo or L-carnitine (2 g bid, orally) for a period of 3 weeks and were then crossed over to the other treatment for an additional 3 weeks. The effect on walking distance at the end of each treatment period was measured by treadmill test. Absolute walking distance rose from 174 +/- 63 m with placebo to 306 +/- 122 m (p less than .01) with carnitine. Biopsy of the ischemic muscle, carried out before and after 15 days of L-carnitine administration in four additional patients, showed that treatment significantly increased total carnitine levels. An additional goal of this study was to ascertain the effects of L-carnitine on the metabolic changes induced by exercise in the affected limb. In six patients under control conditions, arterial and popliteal venous lactate and pyruvate concentrations were determined at rest, when the maximal walking distance was reached, and 5 min after the walking test. Twenty-four hours later, L-carnitine was administered intravenously (3 g as a bolus followed by an infusion of 2 mg/kg/min for 30 min) and metabolic assessments were repeated. Five minutes after the walking test, popliteal venous lactate concentration increased by 107 +/- 16% before treatment and by only 54 +/- 32% (p less than .01) after carnitine. Furthermore, carnitine induced a more rapid recovery to the resting value of the lactate/pyruvate ratio.(ABSTRACT TRUNCATED AT 250 WORDS)