PROMOTIONAL EFFECT OF Sn ON NO OXIDATION OVER Pt/Al2O3 AS PROMISING GAS EXHAUST CATALYTIC CONVERTER. SELECTIVE Pt AND Sn DISPERSION DETERMINATION

NO oxidation was investigated over Pt-Sn/g-Al₂O₃. The addition of Sn to 1%Pt/g-Al₂O₃ enhances NO oxidation to NO₂. This effect is related to the enhancement of chemisorbed oxygen on the metallic surface produced by Sn.     

Borides and vitreous compounds sintered as high-energy fuels

Boron was chosen as fuel in view of its excellent thermodynamic values for combustion, as compared to traditional fuels. The problem of the boron in combustion is the formation of a surface layer of oxide, which delays the ignition process, reducing the performance of the rocket engine. This paper presents a high-energy fuel for rocket engines. It is composed of sintered boron (borides and carbides and vitreous compounds) with a reducing chemical agent. Borides and boron carbide were prepared since the combustion heat of the latter is similar to that of the amorphous boron (in: K.K. Kuo (Ed.), Boron-Based Solid Propellant and Solid Fuel, Vol. 427, CRC Press, Boca Raton, FL, 1993). Several chemical reducing elements were used, such as aluminum, magnesium, and coke. As the raw material for boron, different compounds were used: amorphous boron, boric acid and boron oxide.     

Rapid mutation detection in complex genes by heteroduplex analysis with capillary array electrophoresis

Mutational analysis of large multiexon genes without prevalent mutations is a laborious undertaking that requires the use of a high-throughput scanning technique. The Human Genome Project has enabled the development of powerful techniques for mutation detection in large multiexon genes. We have transferred heteroduplex analysis (HA) by conformation-sensitive gel electrophoresis of the two major breast cancer (BC) predisposing genes, BRCA1 and BRCA2, to a multicapillary DNA sequencer in order to increase the throughput of this technique. This new method that we have called heteroduplex analysis by capillary array electrophoresis (HA-CAE) is based on the use of multiplex-polymerase chain reaction (PCR), different fluorescent labels and HA in a 16-capillary DNA sequencer. To date, a total of 114 different DNA sequence variants (19 insertions/deletions and 95 single-nucleotide substitutions - SNS) of BRCA1 and BRCA2 from 431 unrelated BC families have been successfully detected by HA-CAE. In addition, we have optimized the multiplex-PCR conditions for the colorectal cancer genes MLH1 and MSH2 in order to analyze them by HA-CAE. Both genes have been amplified in 13 multiplex groups, which contain the 35 exons, and their corresponding flanking intronic sequences. MLH1 and MSH2 have been analyzed in nine hereditary nonpolyposis colorectal cancer patients, and we have found six different DNA changes: one complex deletion/insertion mutation in MLH1 exon 19 and another five SNS. Only the complex mutation and one SNS may be classified as cancer-prone mutations. Our experience has revealed that HA-CAE is a simple, fast, reproducible and sensitive method to scan the sequences of complex genes.     

Mass spectrometric study of tricarbonyl (eta(6)-phenyl methanols) of chromium(0)

A mass spectrometric study of several tricarbonyl (eta(6)-phenyl methanols) of chromium(0) was performed. Electron ionization (EI), chemical ionization (CI) and fast atom bombardment (FAB) mass spectra were acquired for each molecule, and compared in order to establish a general fragmentation pattern. The suggested pathways were investigated and confirmed by means of constant b/e linked scans and high resolution data. In addition a Hammett-McLafferty correlation for some peaks derived from the molecular ions was accomplished.     

The Effect of Glass Fibre and a Phosphorus-Containing Flame Retardant on the Flammability of Recycled PET

The availability of scrap poly(ethylene terephthalate) (PET) from post-consumer bottles is increasing as the post-consumer collecting systems are becoming more usual in daily life. PET is well known as a high-performance engineering thermoplastic because of its good thermal stability, chemical resistance, and excellent mechanical properties. Many efforts have been carried out to use this material in housings of electronic applications. However, the flammability of PET is a shortcoming in some of these applications. In this study, our attempt is to incorporate a non-halogenated flame retardant, in form of a phosphorus-containing compound, together with a commercial glass fibre grade to achieve UL94 test V-0 rating for PET. An investigation of thermal stability and flammability (HDT, UL94 V-test) and mechanical (tensile, flexural and impact tests) properties of glass fibre filled PET samples is reported as a function of fraction of flame retardant. This work shows the influence of the filler content and the interfacial filler/matrix adhesion on the flame retardant and the mechanical properties.     

Dynamic Mechanical Behavior of PP/PET/MAPP Blends Filled with Glass Beads

PP/PET/MAPP blends have been filled with 50 wt% of glass beads. The orientation of the PP crystalline phase, the crystallization behavior and the dynamic mechanical response of these materials have been analyzed. The dynamic mechanical response is strongly affected by the presence of the glass beads, being possible to detect the effect of PET and MAPP on the storage modulus and loss factor values. Moreover, the alpha relaxation of the composites is visibly affected by thermal treatments.     

Elastic waves in quasiperiodic structures

We study the transverse and sagittal elastic waves in different quasiperiodic structures by means of the full transfer-matrix technique and surface Green-function matching method. The quasiperiodic structures follow Fibonacci, Thue-Morse and Rudin-Shapiro sequences, respectively. We consider finite structures having stress-free bounding surfaces and different generation orders, including up to more than 1000 interfaces. We obtain the dispersion relations for elastic waves and spatial localization of the different modes. The fragmentation of the spectrum for different sequences is evident for intermediate generation orders, in the case of transverse elastic waves, whereas, for sagittal elastic waves, higher generation orders are needed to show clearly the spectrum fragmentation. The results of Fibonacci and Thue-Morse sequences exhibit similarities not present in the results of Rudin-Shapiro sequences.     

Direct Observation of the Electroadsorptive Effect on Ultrathin Films for Microsensor and Catalytic‐Surface Control

Microchemical sensors and catalytic reactors make use of gases during adsorption in specific ways on selected materials. Fine‐tuning is normally achieved by morphological control and material doping. The latter relates surface properties to the electronic structure of the bulk, and this suggests the possibility of electronic control. Although unusual for catalytic surfaces, such phenomena are sometimes reported for microsensors, but with little understanding of the underlying mechanisms. Herein, direct observation of the electroadsorptive effect by a combination of X‐ray photoelectron spectroscopy and conductivity analysis on nanometre‐thick semiconductor films on buried control electrodes is reported. For the SnO₂/NO₂ model system, NO₃ surface species, which normally decay at the latest within minutes, can be kept stable for 1.5 h with a high coverage of 15 % under appropriate electric fields. This includes uncharged states, too, and implies that nanoelectronic structures provide control over the predominant adsorbate conformation on exterior surfaces and thus opens the field for chemically reactive interfaces with in situ tunability.     

A Direct Synthesis of Aromatic Nitriles from Aldehydes Using a Mexican Bentonite and Microwave or Infrared Irradiation,in Absence of Solvent

An efficient and simple procedure for the direct conversion of aromatic Aldehydes into the corresponding nitriles with hydroxylamine hydrochloride and a Mexican Bentonite via infrared or microwave irradiation.