Silica and Magnesia Dopant Distributions in Alumina by High-Resolution Scanning Secondary Ion Mass Spectrometry

Trace SiO₂ and MgO additive distributions in sintered alumina have been studied using high-resolution scanning secondary ion mass spectrometry (SIMS). When doped with each additive individually, evidence is seen for both strong silicon segregation to grain boundaries ( C _gb/ C _grain similar/congruent 300) in SiO₂-doped alumina and strong magnesium segregation to grain boundaries ( C _gb/ C _grain similar/congruent 400) in MgO-doped alumina. When codoped with both SiO₂ and MgO, segregation of both ions to grain boundaries is reduced by a factor of 5 or more over single doping. The additive concentrations increase proportionally in the grains, and both dopants become more uniformly distributed throughout the bulk. It is concluded that codoping with these additives increases their mutual bulk solid solubility and decreases their interfacial segregation over single doping. The beneficial effect of MgO additions in controlling microstructure development in alumina and improving corrosion resistance to aqueous HF stems from its ability to redistribute silicon ions from grain boundaries into the bulk.     

Isothermal Section of Er-Ag-Sn System at 873 K

The isothermal section of the Er-Ag-Sn system at 873 K was constructed with the use of scanning electron microscopy, energy-dispersive x-ray microanalysis and x-ray powder diffraction. Two ternary compounds were confirmed at this temperature: ErAgSn (LiGaGe structure type, P6₃mc, Z = 2, a = 4.6595(2) Å, c = 7.2872(3) Å) and non-stoichiometric phase ErAg_1?xSn_2+x (Cu₃Au structure type, Pm-3m, Z = 1). For the last one homogeneity range was established (0.08 < x < 0.24) and lattice parameters were determined (a = 4.5007(4), 4.5040(2), 4.5107(1), 4.5412(1) Å for the compositions Er_25.4Ag_23.4Sn_51.2, Er_25.7Ag_23.0Sn_51.3, Er_25.7Ag_21.7Sn_52.6, Er_25.2Ag_18.6Sn_56.2 (at.%) respectively). Melting point of the phase Er_25.7Ag_21.7Sn_52.6 (at.%) was determined to be 1199 K by differential thermal analysis.     

Aryl Bis‐Sulfonamide Inhibitors of IspF from Arabidopsis thaliana and Plasmodium falciparum

2‐Methylerythritol 2,4‐cyclodiphosphate synthase (IspF) is an essential enzyme for the biosynthesis of isoprenoid precursors in plants and many human pathogens. The protein is an attractive target for the development of anti‐infectives and herbicides. Using a photometric assay, a screen of 40 000 compounds on IspF from Arabidopsis thaliana afforded symmetrical aryl bis‐sulfonamides that inhibit IspF from A. thaliana (AtIspF) and Plasmodium falciparum (PfIspF) with IC₅₀ values in the micromolar range. The ortho‐bis‐sulfonamide structural motif is essential for inhibitory activity. The best derivatives obtained by parallel synthesis showed IC₅₀ values of 1.4 μm against PfIspF and 240 nm against AtIspF. Substantial herbicidal activity was observed at a dose of 2 kg ha^?1. Molecular modeling studies served as the basis for an in silico search targeted at the discovery of novel, non‐symmetrical sulfonamide IspF inhibitors. The designed compounds were found to exhibit inhibitory activities in the double‐digit micromolar IC₅₀ range.     

Modeling the evolution and rupture of stretching pendular liquid bridges

A simplified mathematical model and numerical simulations of the governing Navier–Stokes equations are used to predict the shape evolution, rupture distance, and liquid distribution of stretching pendular liquid bridges between two equal-sized spherical solid particles. In the simplified model, the bridge shape is approximated with a parabola, and it is assumed that the surface tension effects dominate the viscous, inertial, and gravitational effects. For the numerical simulations, a commercial Computational Fluid Dynamics (CFD) software package – FLUENT – is used. The rupture distance predictions obtained with both models are compared with experimental data and a reasonable agreement is found. The results of the numerical investigations show that for simulations with negligible viscous, inertial, and gravitational effects, the rupture distance approaches an asymptotic value, which is close to the value predicted by the simplified model. The bridge profiles predicted using the simplified model and the numerical simulation are compared. It is found that a second-order polynomial appropriately represents the stable bridge shape for particles with identical contact angles; however, for liquid bridges between particles with different contact angles, the numerical simulations of the governing Navier–Stokes equations should be used.     

Monolithically integrated μ-capillary electrophoresis with organic light sources and tunable a-Si:H multispectral photodiodes for fluorescence detection

The miniaturization of chemical or biochemical analysis systems to micro- or nanoscale dimension allows dramatic acceleration of chemical processes and a high degree of parallelism. In this paper, we present a monolithically integrated application specific lab-on-microchip device (ALM) [1], [2] for on-chip capillary electrophoresis (μ-CE) with an organic light-emitting diode (OLED) as excitation light source and a tunable a-Si:H multispectral photodiode for colorimetric analysis. The purpose of this work is to adapt the spectral response of a tunable multispectral photodiode to individual fluorescence spectra of different dyes.     

The effect of red pigment on the amyloidization of yeast proteins

The intensity of amyloid-bound thioflavine T fluorescence was studied in crude lysates of yeast strains carrying mutations in the ADE1 or ADE2 genes and accumulating the red pigment (a result of polymerization of aminoimidazoleribotide), and in white isogenic strains--either adenine prototrophs or carrying mutations at the first stages of purine biosynthesis. We found that the red pigment leads to a drop of amyloid content. This result, along with the data on separation of protein polymers of white and red strains in PAGE, suggests that the red pigment inhibits amyloid fibril formation. The differences in transmission of the thioflavine T fluorescence pattern by cytoduction and in blot-hybridization of pellet proteins of red and white [PSI(+) ] strains with Sup35p antibodies confirmed this conclusion. Purified red pigment treatment also led to a decrease of fluorescence intensity of thioflavine T bound to insulin fibrils and to yeast pellet protein aggregates from [PSI(+) ] strains. This suggests red pigment interaction with amyloid fibrils. Comparison of pellet proteins from red and white isogenic strains separated by 2D-electrophoresis followed by MALDI analysis has allowed us to identify 48 pigment-dependent proteins. These proteins mostly belong to functional classes of chaperones and proteins involved in glucose metabolism, closely corresponding to prion-dependent proteins that we characterized previously. Also present were some proteins involved in stress response and proteolysis. We suppose that the red pigment acts by blocking certain sites on amyloid fibrils that, in some cases, can lead in vivo to interfere with their contacts with chaperones and the generation of prion seeds.     

Enabling resilient P2P video streaming: survey and analysis

Peer-to-Peer (P2P) techniques for multimedia streaming have been shown to be a good enhancement to the traditional client/server methods when trying to reduce costs and increase robustness. Due to the fact that P2P systems are highly dynamic, the main challenge that has to be addressed remains supporting the general resilience of the system. Various challenges arise when building a resilient P2P streaming system, such as network failures and system dynamics. In this paper, we first classify the different challenges that face P2P streaming and then present and analyze the possible countermeasures. We classify resilience mechanisms as either core mechanisms, which are part of the system, or as cross-layer mechanisms that use information from different communication layers, which might inflict additional costs. We analyze and present resilience mechanisms from an engineering point of view, such that a system engineer can use our analysis as a guide to build a resilient P2P streaming system with different mechanisms and for various application scenarios.     

Legislative aspects of radiation hazards from both gamma emitters and radon exhalation of concrete containing coal fly ash

Utilization of coal fly ash in concrete construction has clear environmental, technological and economical advantages. At the same time, fly ash is known to have enhanced concentrations of Naturally Occurring Radioactive Materials (NORM). Legislative issues related to the utilization of coal fly ash in concrete construction are analyzed. Different approaches implemented in standards regulating gamma radiation and radon emanation of concrete and other building materials are reviewed. Although radon exhalation rate of concrete containing coal fly ash can be sometimes slightly higher than that of the reference concrete, radon emanation coefficient is usually lower. In view of this, the standards regulating radioactivity of building materials, but not addressing radon emanation properly could be detrimental to the utilization of fly ash in concrete. At the same time, the evaluation of the excess dose caused by building materials for the radon pathway is complicated, and much more research work is required to justify the assumptions of the physical models in the future standards.