Neural network modeling of the preparation process of a siloxane‐organic polyazomethine

Although apparently simple, the polycondensation reaction leading to polyazomethine is difficult to control because of its equilibrium character, the conversion degree being influenced by a series of parameters. The reaction between a siloxanediamine, 1,3‐bis(3‐aminopropyl)tetramethyldisiloxane, and terephthalaldehyde was performed here in solution (in tetrahydrofuran) without by‐products removal and in absence of any catalyst or pH modifier. Different conditions (co‐monomers ratio, dilution, and temperature), considered as input parameters for the process modeling, were varied according to a pre‐established experimental program. The viscosity of the reaction mixture was chosen as output parameter, being monitored with a Haake Viscotester 7 Plus‐L. The process modeling was performed using a hybrid combination of artificial neural networks and differential evolution algorithm, the last one having the role of developing the neural model in an optimal form. The simulation results showed that the methodology provides accurate results, the model predictions being in close correlation with the experimental data. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42552.     

Synthesis of Invar 36 type alloys from elemental and prealloyed powders by mechanical alloying

Invar 36 (Fe₆₄Ni₃₆) nanocrystalline powders were successfully obtained by the mechanical alloying process. The mechanically alloyed Invar 36 powders were obtained from both, Fe–Ni elemental and Fe–Ni₃Fe prealloyed powders. XRD, DSC and magnetic measurements were used to characterise the Invar 36 powders. The lattice parameter evolution versus temperature of Invar 36 powders was investigated by in-situ high-temperature X-ray diffraction (HT-XRD). For both, Invar 36 (Fe, Ni) and Invar 36 (Fe, Ni₃Fe) powders, the lattice parameter values are constant up to about 350°C. The magnetic measurement also indicated that the Invar 36-type alloys are formed after 16?h of milling.     

Crosslinking and grafting ethylene vinyl acetate copolymer with accelerated electrons in the presence of polyfunctional monomers

In this study, we have studied the effects of polyfunctional monomers (PFMs) on physical properties of ethylene vinyl acetate (EVA) copolymer crosslinked with electron beam (EB) or peroxides. The PFMs used were triallylcyanurate, triallylisocyanurate, trimethylolpropane trimethacrylate, zinc diacrylate, and ethylene glycol dimethacrylate. Using PFMs has led to (1) optimum cure time t ₉₀ decrease from 19′25″ to 17′30″–18′45″, (2) scorch time increase from 2′ to maximum 3′45″, (3) increasing the crosslink density of peroxide or EB-cured systems by increasing the efficiency of productive radical reactions. The most efficient PFM for EVA copolymer blends has been triallylisocyanurate. Tensile strength and tear strength of samples crosslinked with EB for all irradiation doses are significantly better than those obtained for samples crosslinked with peroxides (differences up to 190%). The results show that EB irradiation gave the best results     

Neural network-based hybrid models developed for free radical polymerization of styrene

In the present work, the free radical polymerization of styrene is modeled by considering the phenomenology of the process (a simplified model, which does not include the diffusional effects, gel, and glass effects) in combination with an empirical model represented by an artificial neural network. Differential evolution (DE) algorithm, belonging to the class of evolutionary algorithms, is applied for developing the neural models in optimal forms. For improving the results—predicted conversion and molecular weights as function of time, temperature, and initiator concentration—different combinations between phenomenological model and neural network are tested; also, individual and stacked neural networks have been developed for the polymerization process. This methodology based on hybrid models, including neural networks aggregated in stacks, provides accurate results.     

Studying the local character of Raman features of single-walled carbon nanotubes along a bundle using TERS

Here, we show that the Raman intensity of the G-mode in tip-enhanced Raman spectroscopy (TERS) is strongly dependent on the height of the bundle. Moreover, using TERS we are able to position different single-walled carbon nanotubes along a bundle, by correlating the observed radial breathing mode (RBM) with the AFM topography at the measuring point. The frequency of the G^- mode behaves differently in TERS as compared to far-field Raman. Using the RBM frequency, the diameters of the tubes were calculated and a very good agreement with the G^- -mode frequency was observed.     

Study of gradual porous metallic membranes obtained by powder sedimentation

In our preliminary studies the possibility of obtaining sintered porous materials with gradual structure by sedimentation of metallic powder was demonstrated. In this paper we continued our studies on the influencing factors of the sedimentation of metallic powders. Irregular and spherical nickel particles were used having a grain size in the 2–90 μm range measured by the laser scattering particle size analyzer. The particles with irregular shape and larger diameter can sediment faster than the spherical and the smaller diameter particles. The sedimentation rate is also influenced by the sedimentation medium and the quantity of the dispersant agent. Deviations from Stokes law was observed in the case of the irregular particles. The gradual structure is influenced by the sintering regime and the powders characteristics too. The obtained structures were characterized by scanning electron microscopy and mercury porosimetry. The permeability and the filtration fineness were also determined.     

Characterization of Gradual Porous Ceramic Structures Obtained by Powder Sedimentation

Asymmetric membranes present better separation and service characteristics than the symmetric ones. In our preliminary studies the possibility of obtaining sintered porous materials with gradual structure by sedimentation of metallic and ceramic powders was demonstrated. Zirconium silicate (ZrSiO4) particles were used for the manufacturing of the porous supports, and mullite powder was deposited by sedimentation in order to achieve the active layer with pores size gradient. The used powders and the obtained structures were characterized by laser scattering particle size analyzer, scanning electron microscopy and mercury porosimetry. The permeability and the filtration fineness of the structures were also determined. By using a thin active layer made of small particles deposited onto a macro-porous support, one can achieve membranes with high flow rates and filtration fineness in the microfiltration area.     

Glycine fluoromethylketones as SENP-specific activity based probes

We report here the synthesis and biochemical properties of a new peptidyl activity-based probe 1 for SUMO proteases, SENPs. The activity-based probe has at its C terminus a glycine-derived fluoromethylketone moiety as a reactive group designed to target the active-site cysteine of SENPs. Based on a study of the interactions between SENPs and SUMOs, we introduced further design elements that allow the activity-based probe to selectively target SENPs at low micromolar to high nanomolar concentrations. Moreover, 1 out-competes SUMO1 from the reversible SUMO1-SENP1 complex, thus suggesting that 1 and SUMO1 share a common binding site on SENP1.     

Self-Ordered Nanoporous Alumina Templates Formed by Anodization of Aluminum in Oxalic Acid

Anodic aluminum oxide (AAO) membranes with highly ordered nanopores serve as ideal templates for the formation of various nanostructured materials. The procedure of the template preparation is based on a two-step self-organized anodization of aluminum. In the current study, AAO templates were fabricated in 0.3?M oxalic acid under the anodizing potential range of 30?C60?V at an electrolyte temperature of ~5°C. The AAO templates were analyzed using scanning electron microscopy, x-ray diffraction, Fourier-transform infrared spectroscopy, and differential thermal analysis. The as obtained layers are amorphous; the mean pore size is between 40?nm and 75?nm and increases with the increase of the anodization potential. Well-defined pores across the whole aluminum template, a pore density of ~10¹⁰?pores/cm², and a tendency to form a porous structure with hexagonal symmetry were observed.     

EBV-induced expression and HLA-DR-restricted presentation by human B cells of alpha B-crystallin, a candidate autoantigen in multiple sclerosis

The first known human case of heme oxygenase-1 (HO-1) deficiency is presented in this report. The patient is a six-year-old boy with severe growth retardation. He has been suffering from persistent hemolytic anemia characterized by marked erythrocyte fragmentation and intravascular hemolysis, with paradoxical increase of serum haptoglobin and low bilirubin. An abnormal coagulation/fibrinolysis system, associated with elevated thrombomodulin and von Willebrand factor, indicated the presence of severe, persistent endothelial damage. Electron microscopy of renal glomeruli revealed detachment of endothelium, with subendothelial deposition of an unidentified material. Iron deposition was noted in renal and hepatic tissue. Immunohistochemistry of hepatic tissue and immunoblotting of a cadmium-stimulated Epstein-Barr virus-transformed lymphoblastoid cell line (LCL) revealed complete absence of HO-1 production. An LCL derived from the patient was extremely sensitive to hemin-induced cell injury. Sequence analysis of the patient's HO-1 gene revealed complete loss of exon-2 of the maternal allele and a two-nucleotide deletion within exon3 of the paternal allele. Growth retardation, anemia, iron deposition, and vulnerability to stressful injury are all characteristics observed in recently described HO-1 targeted mice. This study presents not only the first human case of HO-1 deficiency but may also provide clues to the key roles played by this important enzyme in vivo.