FTIR investigation of ethylene coordination and polymerization on reduced Cr/SiO2 catalyst

FTIR spectroscopy was applied to study the initial steps of ethylene polymerization on reduced chromia-silica (0.5 wt% Cr/SiO₂). To decrease the speed of the reaction small doses of gas were introduced to the catalyst in each run and C₂D₄ was used to confirm band assignments. At the initial steps of the reaction only ethylene molecules coordinated to probably Cr _A ²⁺ cations were observed. The concentration of such complexes was estimated to be about 50% of the total amount of Cr atoms in the sample. The FTIR spectrum of the polymer formed at the initial doses of C₂H₄ (when [C₂H₄] [Cr]) was found to be slightly different from that formed after excess ethylene was introduced onto the catalyst ([C₂H₄] > [Cr]).     

Hydroxyls nests in defective silicalites and strained structures derived upon dehydroxylation: vibrational properties and theoretical modelling

Defective silicalite, an efficient and selective catalyst in the gas phase Beckmann rearrangement reaction, has been characterised by infrared spectroscopy and by molecular modelling techniques. We report a detailed IR study on the effect of outgassing treatments at increasing temperature on silanols bands and on framework modes. The effect of a temperature decrease up to 100 K (during the IR measurement) on the H-bonding interactions has also been investigated. The interaction of silanols with mesitylene, a probe molecule which cannot penetrate the channels, has been studied in order to distinguish between internal and external OH groups. Molecular mechanics and ab initio methods have also been used to model the structure and the vibrational features of a properly designed nest in order to support the assignments of the IR spectrum.     

Well defined CuI(NO), CuI(NO)2 and CuII(NO)X (X = O− and/or NO 2 − ) complexes in CuI-ZSMS prepared by interaction of H-ZSM5 with gaseous CuCl

In this note an exchange procedure of the acidic protons of H-ZSM5 by Cu^I ions through reaction with CuCl in the gas phase is described. In the so obtained Cu^I-ZSM5 exchanged zeolite the Cu^I ions are in well defined configuration and form with NO mono and di-nitrosyl complexes of high structural and spectroscopic quality. The Cu^I(NO)₂ species are transformed at RT into Cu^II(NO)X (X=O^– and/or NO ₂ ^– ) species which could represent an intermediate in NO decomposition.     

Detecting past attempts to restore two important works of art

Chemistry plays a fundamental role in the preservation of our heritage. Artistic and archaeological materials deteriorate over time due to their interaction with the environment, and human intervention can trigger unexpected deterioration pathways. Previous intervention can also sometimes obscure information regarding the original techniques or the materials used to execute the artwork. Our studies of past intervention and attempts to conserve the lunette of the church of Santa Maria la Vetere in Militello Val di Catania (Italy) and Donatello's carved marble panels of the pulpit of the Duomo of Prato (Italy) are discussed as two examples of how chemistry can provide guidance for conservators and fill gaps in the known life of works of art.     

The contribution of attention in virtual moped riding training of teenagers

Riding a moped, like many other everyday activities, is a complex behavior in which attention plays a crucial role. This study aims to investigate the role of attention in enhancing the skills required to ride a moped simulator. Two experiments were conducted with 207 and 60 students (14–15 years old), respectively, using a moped simulator to ride on 12 different tracks. The assignment was to ride safely and avoid hazards. In experiment 1, we divided the hazard scenes of the tracks on the basis of the fact that a shift in attention was required to escape the danger. We showed that during the riding training, when no attentional shift was required, the ability to avoid hazards was constantly higher. In experiment 2, participants were asked to cope with the same basic experimental setting but with an additional attentive task. The results showed that they performed in such a way that not only did the attentive task not impair their performance, but it also produced an improvement in the ability to shift attentional focus, preserving performance efficiency. On the basis of these data, it can be claimed that, primarily, attentional shift plays a prominent role in accounting for accident circumstances. Secondarily, it can be claimed that attentional training contributes to improved processing efficiency so as to prevent mishaps.     

An XRD,FTIR and TPD investigation of NO2 surface adsorption sites of δ, γ Al2O3 and barium supported δ, γ Al2O3

This work reviews the use of terpenes available from renewable resources in the fine chemicals industry. Different products and processes are discussed. Transformations of terpenes involving isomerization, hydration, condensation, hydroformylation, hydrogenation, cyclization, oxidation, rearrangement, and ring contraction/enlargement are routes to produce a variety of compounds of interest to the pharmaceutical, agrochemical, and flavors and fragrances industries.     

Endovascular stenting of an unprotected left main coronary artery stenosis in a heart transplant patient

Endoluminal revascularizaion of left main coronary artery vessels is considered to be relatively contraindicated because of a high procedural mortality and restenosis rate. This report describes the first successful case of endovascular stenting in an unprotected left main coronary artery stenosis in a heart transplant patient.     

Ionic clusters in zeolites formed by interaction with sodium solutions in liquid ammonia

An alternative route for the preparation of Na ₄ ³⁺ paramagnetic clusters in Y zeolites is described involving contact of the solid with a solution of sodium in liquid ammonia. Besides the EPR signal of the cluster a second signal, likely due to be a solvated electron in the sodalitic cage, is also observed.     

Holographic interferometry with multiple wavelengths

One of the unsolved problems in the well-established field of holographic interferometry is identification of zeroth-order fringes in cases in which the locations of zero displacement are unknown. We offer a simple solution: By making the double-exposure hologram of a white object in full color by using three or more wavelengths, the zeroth-order fringes will be indentified by their white color.