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]).     

Optimum Receiver Design for Correlated Rician Fading MIMO Channels with Pilot-Aided Detection

Two structures based on pilot symbol-aided channel receiver estimation are considered for the separately-correlated Rician fading MIMO channel. Mismatched receiver, which A decodes the received signal by first using maximum-likelihood (ML) or mean- minimum error square (MMSE) estimation of the MIMO channel matrix, and then by assuming that the estimate is exact. An optimum receiver, which does not estimate explicitly the matrix but jointly channel processes the received pilot and samples assuming known channel distribution.     

Metal sols as a useful tool for heterogeneous gold catalyst preparation: reinvestigation of a liquid phase oxidation

Differently stabilised metal sols have been used as precursors in the preparation of heterogeneous gold catalysts for liquid phase oxidation in water solution. The methodology of sols generation appears to be fundamental to obtaining nanoparticles; the support, instead, plays an important role in maintaining particle dimension and morphology.

Three different materials (γ-Al₂O₃, SiO₂ and activated carbon) have been used as the supporting agents for different gold sols that were obtained by reducing HAuCl₄ with NaBH₄ in the presence of polyvinylalcohol (PVA) or polyvinylpirrolidone (PVP) and with the tetrakis(hydroxymethyl)phosphonium chloride (THPC)/NaOH system. During the immobilisation step, the maintenance of the particle dimension observed in solution depends on both the support and the type of sol. The gold particle mean size of the colloidal suspension is more easily maintained on oxidic supports than on carbon, the latter apparently needing both steric and polar stabilisation of the gold particle.

Comparison of Au/γ-Al₂O₃ and Au/C catalyst activity in the liquid phase oxidation of ethylene glycol to glycolate highlighted the peculiarity of gold on carbon catalysts; in fact, the normally observed trend of reactivity is partially reversed, medium sized gold particle being the most active.     

Chemical treatment on alumina–zirconia composites inducing apatite formation with maintained mechanical properties

Alumina–zirconia composites with submicrometric grain size were surface modified with the purpose to induce bioactivity using several chemical treatments. Among them, a quick attack by phosphoric acid induced on Zirconia Toughned Alumina (80–20 wt%) the formation of apatite-like calcium phosphate phases after immersion in simulated body fluid, indicating bioactivity induction. Such a treatment does not reduce the strength, hardness and ageing properties of this ceramic material, making it a suitable method for biomedical applications. Surface properties, topography and microstructure of oxide ceramics are also discussed.     

Pre-feasibility analysis of an energy supply system for Southern Europe: Technical aspects

Technical aspects of the feasibility of energy transmission from hydroelectric power plants in Zaire to southern Europe, and to Italy in particular, have been studied. Three alternatives were considered: electric power transmission, gaseous hydrogen pipeline, and methylcyclohexane/toluene loop cycle. The technical feasibility of each alternative, also for a mid-term prospect, and energy losses were examined and evaluated. A comparison, from an energetic point of view, was also carried out among the three systems by varying the ratio between hydrogen and electric power required by the users. The high values of the energy transmission factor make this energy supply system very attractive. Depending on the sharing of the energy required for final uses, a double transportation system, based on electric power together with hydrogen, could be convenient. Indeed, if a very high amount of hydrogen is required by the users, a system based on hydrogen would be preferable.     

Preparation and Characterization of Pt/Al-ZSM-5 Catalysts and their Reactivities for the Oxidation of CO with N2O at Low Temperatures

Al-ZSM-5 was prepared by treating H-ZSM-5 with an aqueous solution of Al(NO₃)₃ and used as a support for Pt catalysts. The Pt-loaded Al-ZSM-5 acts as an efficient catalyst for CO oxidation with N₂O at 273 K. TEM investigations revealed that Pt clusters with an average particle size of around 1–1.5 nm were homogeneously dispersed within Al-ZSM-5. Moreover, FT-IR and XPS analyses indicated that the small Al₂O₃ clusters formed within Al-ZSM-5 plays a significant role in the formation of highly dispersed Pt clusters within the pore structure of the ZSM-5 zeolite, leading to the high catalytic activity of Pt/Al-ZSM-5 as compared to Pt/ZSM-5.     

Surface structure of Ni/MgO catalysts: Effects of carbon and hydrogen on the reactivity towards CO. HRTEM and FTIR studies

CO adsorption on high loading Ni/MgO samples treated at 800 and 900°C has been studied by using IR spectroscopy. Linear and bridged monocarbonyls are produced under low CO pressure and the Boudouard reaction occurs producing C, adsorbed on the metal particles, and CO₂, stabilized on the MgO matrix. Effects of hydrogen and carbon on surface reactivity have been studied. The morphology of the catalysts and of carbonaceous deposits produced by heating in CO at high temperature are examined by HRTEM.     

Water-Soluble Ruthenium(III)-Dimethyl Sulfoxide Complexes: Chemical Behaviour and Pharmaceutical Properties

In this paper we report a review of the results obtained in the last few years by our group in the development of ruthenium(III) complexes characterized by the presence of sulfoxide ligands and endowed with antitumor properties. In particular, we will focus on ruthenates of general formula Na[trans-RuCl(4)(R(1)R(2)SO)(L)], where R(1)R(2)SO = dimethylsulfoxide (DMSO) or tetramethylenesulfoxide (TMSO) and L = nitrogen donor ligand. The chemical behavior of these complexes has been studied by means of spectroscopic techniques both in slightly acidic distilled water and in phosphate buffered solution at physiological pH. The influence of biological reductants on the chemical behavior is also described. The antitumor properties have been investigated on a number of experimental tumors. Out of the effects observed, notheworthy appears the capability of the tested ruthenates to control the metastatic dissemination of solid metastasizing tumors. The analysis of the antimetastatic action, made in particular on the MCa mammary carcinoma of CBA mouse, has demonstrated a therapeutic value for these complexes which are able to significantly prolong the survival time of the treated animals. The antimetastatic effect is not attributable to a specific cytotoxicity for metastatic tumor cells although in vitro experiments on pBR322 double stranded DNA has shown that the test ruthenates bind to the macromolecule, causing breaks corresponding to almost all bases, except than thymine, and are able to cause interstrand bonds, depending on the nature of the complex being tested, some of which results active as cisplatin itself.     

Antitumor Trans Platinum DNA Adducts: NMR and HPLC Study of the Interaction Between a trans-Pt Iminoether Complex and the Deoxy Decamer d(CCTCGCTCTC).d(GAGAGCGAGG)

The single-stranded oligonucleotide 5'-d(CCTCGCTCTC) (I) was reacted with the antitumor trans platinum iminoderivative trans-[PtCl(2){E-HN = C(OMe)Me}(2)] (trans-EE) and subsequently annealed with its complementary strand 5'-d(GAGAGCGAGG) (II). The platinated duplex was characterized by 1D and 2D proton NMR spectroscopy at 600 MHz. In agreement with previous studies by different techniques trans-EE was found to form a monofunctional adduct with the duplex involving the guanine residue. The modification by trans-EE has been found to induce only minor local distortion in the duplex geometry. Two key crosspeaks observed in the NOESY map corresponding to a close contact between G5-H8 and the methoxy and the methyl group, respectively, enabled us to dock the trans-EE complex with the duplex by geometry optimization. The results support the idea that the antitumor activity of trans-EE is related to lesion of DNA fundamentally different from that of cisplatin. Unexpectedly, the NOESY spectra indicated that at the high NaCl concentration used (0.2 M) the duplex was found to undergo slow deplatination. This was subsequently proved by HPLC. In a separate experiment on platination of the single strand in a salt free environment the HPLC analysis showed that the monofunctional adduct was not deplatinated, however, after 24 hours, additidnal minor isomers were detected.     

Non-idealities Compensation in Full-Digital Receivers with Application to Ultra-Wide Band

Nowadays many transceivers adhere to full-digital design principles, with the basic operations performed in the analog domain (filtering, down-conversion) and the whole remaining processing postponed to the digital domain (including matched filtering and synchronization). Though the operations in the analog front-end are ideally reversible, hence no signal degradation should occur before the analog-to-digital conversion (thus preserving the information integrity), however the intrinsic non-idealities in the circuitry may introduce a certain level of distortion. In this paper we provide a simple and flexible approach for the compensation of these effects. We derive useful formulas for obtaining a digital compensation filter by means of a direct transformation of the analog system coefficients. This allows to easily perform the compensation in the digital domain via fast Fourier transform. To illustrate the procedure, the case-study of a ultra-wide band receiver is addressed. Numerical results show that an improvement of more than 1 dB can be obtained at bit-error rate of interest for the applications. Sample code is also provided for an easy implementation.