Porous Garnet Coatings Tailoring the Emissivity of Thermostructural Materials

The power radiated by a surface influences the energy transfer processes following a T⁴ slope. It is therefore clear that, at high temperature, the study and control of spectral emissivity of materials play a key role in many important technologies: re-entry-vehicle thermal protection shields, high temperature radiators, selective emitters in thermophotovoltaic generators, etc. We have developed a class of thick porous garnet coatings that may raise or lower the spectral emissivity of thermostructural materials in the VIS, NIR, and IR regions. The porosity of the coatings nearly cancels any emission contribution from the underlying materials due to the scattering in the inhomogeneous system: pore/high refraction garnet. The yttrium aluminum garnet polycrystals vary their emissivity as a function of the doping rare earth elements they contain. We achieved an emission control capability in the range 700–3000 nm. Porous coatings have been prepared from ceramic slips containing a reactive colloidal phase and rare earth garnet powders prepared by drying and calcining mixed oxide aqueous gels. Garnet coatings containing Er, Yb, and Tm were prepared with thickness ranging between 50 and 400 microns. The coatings have been investigated by morphological and microstructural studies. A dedicated experimental set up has been developed to measure the spectral emissivity up to 1700 K under different heating conditions.     

Silica gel supported phosphonium salts as micellar and phase transfer catalysts

Phosphonium salts immobilized on silica gel have been found to be both micellar and phase-transfer catalysts. They are able to exchange their parent anions with the anions present in an aqueous solution and promote, in catalytic amounts, the decarboxylation of 6-nitrobenzisoxazole-3-carboxylate to give 2-cyano-5-nitrophenolate, a test for micellar catalysis.     

Copper(I) and copper(II) inhibit Aβ peptides proteolysis by insulin-degrading enzyme differently: implications for metallostasis alteration in Alzheimer's disease

Accumulation of neurotoxic amyloid-β peptide (Aβ) and alteration of metal homeostasis (metallostasis) in the brain are two main factors that have been very often associated with neurodegenerative diseases, such as Alzheimer's disease (AD). Aβ is constantly produced from the amyloidprecursor-protein APP precursor and immediately catabolized under normal conditions, whereas dysmetabolism of Aβ and/or metal ions seems to lead to a pathological deposition. Although insulin-degrading enzyme (IDE) is the main metalloprotease involved in Aβ degradation in the brain being up-regulated in some areas of AD brains, the role of IDE for the onset and development of AD is far from being understood. Moreover, the biomolecular mechanisms involved in the recognition and interaction between IDE and its substrates are still obscure. In spite of the important role of metals (such as copper, aluminum, and zinc), which has brought us to propose a "metal hypothesis of AD", a targeted study of the effect of metallostasis on IDE activity has never been carried out. In this work, we have investigated the role that various metal ions (i.e., Cu(2+), Cu(+), Zn(2+), Ag(+), and Al(3+)) play in modulating the interaction between IDE and two Aβ peptide fragments, namely Aβ(1-16) and Aβ(16-28). It was therefore possible to identify the direct effect that such metal ions have on IDE structure and enzymatic activity without interferences caused by metal-induced substrate modifications. Mass spectrometry and kinetic studies revealed that, among all the metal ions tested, only Cu(2+), Cu(+), and Ag(+) have an inhibitory effect on IDE activity. Moreover, the inhibition of copper(II) is reversed by adding zinc(II), whereas the monovalent cations affect the enzyme activity irreversibly. The molecular basis of their action on the enzyme is also discussed on the basis of computational investigations.     

Non-destructive defect characterization of concrete structures reinforced by means of FRP

The aim of this work is to develop a reliable and precise non-destructive testing technique based on infrared thermography and post processing by means of neural networks. In particular, the experimental procedure to be implemented consists mainly in the “impulsive” heating of the structure and in the analysis of the superficial thermal response by means of a thermocamera. The procedure requires a detailed set-up, in order to assess its feasibility. In this work is presented the case study of a concrete structure strengthened by bonded FRP, with imposed well-known defects. The results obtained by means of infrared thermography were compared with results obtained by ultrasonic testing.     

Reaction of primary aromatic amines with alkyl carbonates over NaY faujasite: a convenient and selective access to mono-N-alkyl anilines.

At atmospheric pressure and at 130-160 degrees C, primary aromatic amines (p-XC6H4NH2, X = H, Cl, NO2) are mono-N-alkylated in a single step, with symmetrical and asymmetrical dialkyl carbonates [ROCOOR', R = Me, R' = MeO(CH2)2O(CH2)2; R = R' = Et; R = R' = benzyl; R = R' = allyl; R = Et, R' = MeO(CH2)2O(CH2)2], in the presence of a commercially available NaY faujasite. No solvents are required. Mono-N-alkyl anilines are obtained with a very high selectivity (90-97%), in good to excellent yields (68-94%), on a preparative scale. In the presence of triglyme as a solvent, the mono-N-alkyl selectivity is independent of concentration and polarity factors. The reaction probably takes place within the polar zeolite cavities, and through the combined effect of the dual acid-base properties of the catalyst.     

Highly chemoselective methylation and esterification reactions with dimethyl carbonate in the presence of NaY faujasite. The case of mercaptophenols, mercaptobenzoic acids, and carboxylic acids bearing OH substituents

In the presence of NaY faujasite, the reactions of dimethyl carbonate (DMC) with several ambident nucleophiles such as o- and p-mercaptophenols (1a,b), o- and p-mercaptobenzoic acids (2a,b), o- and p-hydroxybenzoic acids (3a,b), mandelic and phenyllactic acids (4, 5), have been explored under batch conditions. Highly chemoselective reactions can be performed: at 150 degrees C, compounds 1 and 2 undergo only a S-methylation reaction, without affecting OH and CO2H groups; at 165 degrees C, acids 3-5 form the corresponding methyl esters, while both their aromatic and aliphatic OH substituents are fully preserved from methylation and/or transesterification processes. Typical selectivities are of 90-98% and isolated yields of products (S-methyl derivatives and methyl esters, respectively) are in the range of 85-96%. A comparative study with K2CO3 as a catalyst is also reported. Although the base (K2CO3) turns out to be more active than the zeolite, the chemoselectivity is elusive: compounds 2a,b undergo simultaneous S-methylation and esterification reactions, and acids 3-5 yield complex mixtures of products of O-methylation, O-methoxycarbonylation, and esterification of their OH and CO2H groups, respectively. Overall, the combined use of a nontoxic reagent/solvent (DMC) and a safe promoter (NaY) imparts a genuine ecofriendly nature to the investigated synthesis.     

Reaction of functionalized anilines with dimethyl carbonate over NaY faujasite. 3. chemoselectivity toward mono-N-methylation

In the presence of NaY faujasite, dimethyl carbonate (MeOCO(2)Me, DMC) is a highly chemoselective methylating agent of functionalized anilines such as aminophenols (1), aminobenzyl alcohols (2), aminobenzoic acids (3), and aminobenzamides (4). The reaction proceeds with the exclusive formation of N-methylanilines without any concurrent O-methylation or N-/O-methoxy carbonylation side processes. Particularly, only mono-N-methyl derivatives [XC(6)H(4)NHMe, X = o-, m-, and p-OH; o- and p-CH(2)OH; o- and p-CO(2)H; o- and p-CONH(2)] are obtained with selectivity up to 99% and isolated yields of 74-99%. DMC, which usually promotes methylations only at T > 120 degrees C, is activated by the zeolite catalyst and it reacts with compounds 1, 2, and 4, at 90 degrees C. Aminobenzoic acids (3) require a higher reaction temperature (> or =130 degrees C).