Application of TG/FTIR to the study of the regeneration process of husy and HZSM5 zeolites

The effect of regeneration conditions on the composition of the gases evolved during the catalytic pyrolysis of low density (LDPE) and high density polyethylene (HDPE) with HUSY and HZSM5 catalysts has been analysed by the TG/FTIR technique. When regenerated HUSY was employed, the evolution of the gases obtained was similar to that with fresh HUSY, indicating that the regeneration treatment did not affect its properties. Nevertheless with HZSM5, as the regeneration temperature was higher, the composition of the gases gradually became more similar to that evolved in the thermal process.     

Sea quark polarization and semi-inclusive DIS data

We investigate the potential impact of forthcoming Jefferson Lab semi-inclusive polarized deep inelastic scattering proton measurements in the determination of the sea quark polarization in the nucleons by means of a next to leading order global QCD analysis. Specifically, we estimate the resulting improvement in the constraints on polarized parton densities for different flavors, which is found to be significant for up and strange quarks, and the correlation between remaining uncertainty ranges for each of the parton species. PACS 12.38.Bx, 13.85.Ni     

Sylow normalizers and character tables, II

Suppose thatG is a finitep-solvable group and letPε Syl _p (G). In this note, we prove that the character table ofG determines ifN _G(itP)/P is abelian. Research partially supported by DGICYT.     

Continuous chromatographic separation process: simulated moving bed allowing simultaneous withdrawal of three fractions

Continuous counter-current chromatographic separation has been carried out in a simulated moving bed system (SMB). We have worked with a SMB pilot plant (8 columns, 4.4 litres of resin each) which allows the continuous withdrawal of two different fractions. A mixture of glucose-fructose has been separated. To calculate the concentration profile within the separator an axial dispersed plug flow model and an equilibrium stage model have been employed; software has been created to simulate the behaviour of the separator. The necessary parameters of the mode: the adsorption equilibrium constant, the height equivalent to a theoretical plate and the bed voidage, have been acquired experimentally from elution chromatography measurements. The results calculated by simulation give a good representation of the experimental concentration profiles; other separations like xylitol-arabitol have been simulated. The influence of some factors like desorbent flow-rate, feed flow-rate and the bed voidage have been studied using the software. Once the system has worked in a two withdrawal way, an extension of the pilot plant has been constructed so as to obtain a third one. The necessary parameters of the three withdrawal model will be studied.     

New asymptotic representations of the noncentral t-distribution

New asymptotic approximations of the noncentral t distribution are given a generalization of the Student's t distribution. Using new integral representations, we give new asymptotic expansions not only for large values of the noncentrality parameter but also for large values of the degrees of freedom parameter. In some cases, we accept more than one large parameter. These results are not only in terms of elementary functions, but also in terms of the complementary error function and the incomplete gamma function. A number of numerical tests demonstrate the performance of the asymptotic approximations.     

Analysis of the escape in systems with four exit channels

In this paper, we have performed a numerical investigation of the escape of a particle from two different dynamical systems with the same number of exit channels. We have chosen specific values of the parameters of the systems so that the openings of the potential well in both systems are approximately of the same size. We have found that, in the galactic system, the distribution of the times of escape follows a sequential pattern that has never been detected before. Moreover, we have proved that this pattern is directly related to the geometry of the stable manifolds to the Lyapunov orbits located at the openings of the potential. Finally, we have shown that the different nature of the two systems affects the way the escape occurs, due to the difference in the geometry of the manifolds to the Lyapunov orbits in both systems.     

Synthesis of an [(NHC)2Pd(SiMe3)2] Complex and Catalytic cis‐Bis(silyl)ations of Alkynes with Unactivated Disilanes

The novel complex cis‐[(ITMe)₂Pd(SiMe₃)₂ (ITMe=1,3,4,5‐tetramethylimidazol‐2‐ylidene) has been synthesized by mild oxidative cleavage of Me₃SiSiMe₃ using [(ITMe)₂Pd⁰]. The use of this complex as precatalyst for the cis‐bis(silyl)ation of alkynes using unactivated disilanes is reported.     

Textile/Metal–Organic‐Framework Composites as Self‐Detoxifying Filters for Chemical‐Warfare Agents

The current technology of air‐filtration materials for protection against highly toxic chemicals, that is, chemical‐warfare agents, is mainly based on the broad and effective adsorptive properties of hydrophobic activated carbons. However, adsorption does not prevent these materials from behaving as secondary emitters once they are contaminated. Thus, the development of efficient self‐cleaning filters is of high interest. Herein, we report how we can take advantage of the improved phosphotriesterase catalytic activity of lithium alkoxide doped zirconium(IV) metal–organic framework (MOF) materials to develop advanced self‐detoxifying adsorbents of chemical‐warfare agents containing hydrolysable P? F, P? O, and C? Cl bonds. Moreover, we also show that it is possible to integrate these materials onto textiles, thereby combining air‐permeation properties of the textiles with the self‐detoxifying properties of the MOF material.     

Covalently Binding Atomically Designed Au9 Clusters to Chemically Modified Graphene

Atomic‐resolution transmission electron microscopy was used to identify individual Au₉ clusters on a sulfur‐functionalized graphene surface. The clusters were preformed in solution and covalently attached to the surface without any dispersion or aggregation. Comparison of the experimental images with simulations allowed the rotational motion, without lateral displacement, of individual clusters to be discerned, thereby demonstrating a robust covalent attachment of intact clusters to the graphene surface.