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The exchange of sodium zeolite X and sodium zeolite A with cesium solutions is described. The presence of cesium cations in different sites of zeolite networks is examined.

Cesium-exchanged A and X zeolites are loaded with cesium acetate species and thermally treated in order to inhibit the mobility of exchangeable cesium cations. The cesium impregnated species did not induce strong structural modifications if they are used in small amounts, but they promote transformation toward cesium orthosilicate if they are loaded in amounts as high as 2 meq/g zeolite.

A study on the analysis of the X-ray diffraction patterns and the AL MAS NMR spectra that showed the shell of the naoncapsules was made up of Al13 tridecamers ordered in a noncrystalline symmetry was conducted. The study revealed that the transformation of the phase was made up of ordered Al13 tridecamers into a noncrystalline alumina was a pseudomorphic.

Phosphated alumina gels were prepared by the sol-gel method. It is concluded that the aging time is crucial parameter in the formation of coordinately unsaturated sites of alumina.

Nitromethane was used as a NMR probe molecule to monitor the basicity of the surface of a series of oxides. The chemical shift of the carbon of nitromethane adsorbed on various oxides was shown to be correlated with the heat of adsorption of carbon dioxide on the same material. The results show that one may use the chemical shift of nitromethane as a measure of basicity of these oxide surfaces.

This work presents a new decision making criterion for analysis of multiobjective optimization problems, based on the evaluation of the optimum solutions in the Pareto set. This new technique allows for discrimination among the solutions that constitute the Pareto set, so that a single alternative (the least sensitive one) is selected for real implementation. In order to do that, the effects of process uncertainties on the variable responses are analyzed individually, with the help of the process model, and used to compute a sensitivity index. The proposed technique was applied to three distinct problems, and the obtained results showed that the method is able to discriminate the solutions successfully, allowing for appropriate selection of the best candidates for real implementation among the many candidates in the Pareto set. [ABSTRACT FROM AUTHOR]

Collagen–polyvinylpyrrolidone(C–PVP) is a copolymerthat is generated from the γ irradiation of a mixture of typeI collagen and low-molecular-weight PVP. It is characterized by immunomodulatory,fibrolytic, and antifibrotic properties. Here, we used various physicochemicaland biological strategies to characterize the structure, biochemicalsusceptibility, as well as its effects on metabolic activity in fibroblasts.C–PVP contained 16 times more PVP than collagen, but only 55.8%of PVP was bonded. Nevertheless, the remaining PVP exerted strongstructural activity due to the existence of weak bonds that providedshielding in the NMR spectra. On SEM and AFM, freeze-dried C–PVPappeared as a film that uniformly covered the collagen fibers. Sizeanalysis revealed the presence of abundant PVP molecules in the solutionof the copolymer with a unique dimension related to macromolecularcombinations. Calorimetric analysis showed that the copolymer in solutionexhibited structural changes at 110 °C, whereas the lyophilizedform showed such changes at temperatures below 50 °C. The copolymerpresented a rheopectic behavior, with a predominant effect of thecollagen. C–PVP had biological effects on the expression ofintegrin α2and prolyl-hydroxylase but did not interactwith cells through the collagen receptors because it did not inhibitor slow contraction. [ABSTRACT FROM AUTHOR]

Hydrotaldte-like compounds were synthesized by coprecipitation using a constant-pH method. Aluminum was introduced in the form of an octahedral aluminum fluorine complex during the synthesis. Controlling the pH during the synthesis ensured that aluminum fluorine did not decompose to tetrahedral species but remained in the octahedral (AlF6)3- form to be incorporated into brucite-like sheets. The physicochemical, thermal, and spectroscopic characterizations showed significant modifications by fluorine introduction regarding structural, textural, and adsorption properties. The memory effect of fluorinated hydrotalcites differed from the memory effect commonly observed in fluorine-free hydrotalcites. Nitromethane adsorption showed that the basicity of hydrotaldte was greatly modified by the fluorine loading. [ABSTRACT FROM AUTHOR]

The carbonation process of a calcined Mg-Al layered double hydroxide (LDH) was systematically analyzed at low temperatures, varying the relative humidity. Qualitative and quantitative experiments were performed. In a first set of experiments, the relative humidity was varied while maintaining a constant temperature. Characterization of the rehydrated products by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR) and solid-state NMR revealed that the samples did not recover the LDH structure; instead hydrated MgCO3 was produced. The results were compared with similar experiments performed on magnesium oxide for comparison purposes. Then, in the second set of experiments, a kinetic analysis was performed. The results showed that the highest CO2 capture was obtained at 50 °C and 70% of relative humidity, with a CO2 absorption capacity of 2.13 mmol/g. [ABSTRACT FROM AUTHOR]

The article describes a low-cost thermocouple signal-conditioning module, which was built using the AD594C chip from Analog Devices Inc. This chip compensates for the drawbacks of the thermocouple because it amplifies the signal and provides the cold-junction temperature compensation. Thermocouples are widely used in industrial and laboratory activities. They are formed by two different metals that are typically welded together. The junction between the two metals generates a voltage that is temperature dependent, thus the voltage can be used to determine the temperature. The results show good linearity and reproducibility of the module. After testing, the module has been used to monitor the temperature of polymerization reactors in the laboratories.

The water-stable material NOTT-401 was investigated for CO 2 capture under humid conditions. Water adsorption properties of NOTT-401 were studied, and their correlation with CO 2 sequestration at different relative humidities (RHs) showed that the CO 2 capture increased from 1.2 wt % (anhydrous conditions) to 3.9 wt % under 5% RH at 30 °C, representing a 3.2-fold improvement., Competing Interests: The authors declare no competing financial interest.

The rehydration process of a calcined MgAl-layered double hydroxide (LDH) with a Mg/Al molar ratio of 3 was systematically analyzed at different temperatures and relative humidity. Qualitative and quantitative experiments were done. In the first set of samples, the temperature or the relative humidity was varied, fixing the second variable. Both adsorption and absorption phenomena were present; absorption process was associated to the LDH regeneration. Of course, in all cases the LDH regeneration was confirmed by other techniques such as TGA, solid state NMR, and SAXS. In the second set of experiments, a kinetic analysis was performed, the results allowed to obtain different activation enthalpies for the LDH regeneration as a function of the relative humidity. The activation enthalpies varied from 137.6 to 83.3 kJ/mol as a function of the relative humidity (50 and 80%, respectively). All these experiments showed that LDH regeneration is highly dependent on the temperature and relative humidity.

Microwave irradiated lamellar double hydroxides containing different divalent metals (Mn2+, Zn2+, or Mg2+) were prepared with Al3+ as the trivalent metal. Samples containing Mn2+ and Zn2+ were unstable at 400 degrees C, leading to formation of mixed oxides and spinel phases. Acid-base properties of the samples were characterized by nitromethane and CO2 adsorption followed by FTIR spectroscopy. Decomposition of adsorbed nitromethane leads to isocyanate species that acts as probe molecules of acid-base sites at the surface. These properties determine the ability of materials to retain CO2. Indeed, whereas Mn-O sites are able to interact directly with CO2 molecules, Mg-O and Zn-O are able to form carbonate species as a result of the CO2 sorption.

Lithium cuprate (Li(2)CuO(2)) was prepared by solid state reaction, using different quantities of lithium excess, which produced nonstoichiometric ceramics, Li(2+x)CuO(2+x/2). These ceramics were characterized by X-ray diffraction, transmission and scanning electron microscopies, solid state nuclear magnetic resonance, and atomic absorption. The results obtained showed that lithium excess is located mainly into the Li(2)CuO(2) interlayers forming nanoparticles of a different phase, perhaps lithium oxide. Additionally, the lithium excess produced morphological changed at a micrometric and nanometric levels. As lithium excess increased, the particle size increased as well and it formed some kind of filament-like structures. It was explained in terms sintering, due to the high mobility of lithium atoms. On the other hand, all these ceramics were tested as CO(2) captors, presenting encouraging properties through a chemisorption process. As expected, the CO(2) absorption increased as a function of total lithium contained into the ceramics. Finally, it was performed a kinetic analysis of the CO(2) absorption.

Layers of a layered double hydroxide, containing aluminum 4-fold coordinated, were partially folded in order to obtain a fibrous hydrotalcite-like compound. The hydrotalcite layers, in the presence of an anionic surfactant (sodium dodecyl sulfate) after hydrothermal treatment for 2 weeks, acquire a mesoporous-like arrangement. The transformation was monitored by techniques sensitive to structural and textural properties. Results suggest that brucite-like layers can be joined throughout unsaturated coordinated aluminum, that is, tetrahedral aluminum which links through hydrogen bonds to form aluminum octahedrally coordinated. The fractal dimension parameter was very sensitive to evolution from layered to fibrous hydrotalcites.

The synthesis of samples by the sol-gel method with aluminum tri-sec-butoxide as cation precursor, 2-propanol as solvent, and sulfuric acid as hydrolysis catalyst gave rise to nanocapsules with an average diameter of 20 nm and a shell thickness of 3.5 nm. The analysis of the X-ray diffraction patterns and the 27Al MAS NMR spectra showed that the shell of the nanocapsules was made up of Al13 tridecamers ordered in a noncrystalline symmetry. The interaction between the capsule's shells opened the capsule structure, producing curved fibers, but maintaining the atomic local order. This opening of the capsules favored the reordering of the atomic local order of Al13 tridecamers into the one of crystalline boehmite, when the sample was aged at room temperature for several days; it also increased the pore volume and the specific surface area of the sample. The crystallization transformed the curved fibers into rods made of small crystalline boehmite bars. The capsule morphology was preserved after calcining the nonaged sample at 700 degrees C, indicating that the transformation of the phase made up of ordered Al13 tridecamers into a noncrystalline alumina was pseudomorphic. We describe and partially explain one of the possible atomic ordering evolutions from the one of an isolated Al13 tridecamer, to the phase forming the nanocapsules shell, until eventually coming to the ordering corresponding to boehmite crystalline rods.