Adsorption of organics on MSC5A in supercritical CO2, chromatographic measurements & stop & go simulation

Chromatographic measurements were made for the adsorption of benzene, toluene and m-xylene on molecular sieving carbon (MSC) in supercritical fluid CO₂ mixed with organics. Supercritical chromatograph packed with MSC was used to detect pulse responses of organics. Adsorption equilibria and adsorption dynamics parameters for organics were obtained by moment analysis of the response peaks. Dependences of adsorption equilibrium constants, K ^?, and micropore diffusivity,?D, on the amount adsorbed were examined. The dependencies of adsorption equilibrium constants, K ^?, and micropore diffusivity, D, of benzene, toluene and m-xylene, on molarity of benzene with each parameters of temperature or pressure were obtained. It was found that the values of K ^? and D for an organic substance depended on the amount adsorbed of other organics strongly. And stop & go method was used as simulation method of perturbation chromatography for investigating adsorption equilibrium and rate. Numerical solution for multicomponent chromatogram in time domain could be obtained by appropriate model equations with experimental conditions. This simulated chromatogram can be compared with experimental chromatogram to determine the adsorption equilibrium and rate parameters. In addition, molecular simulation of multicomponent adsorption equilibria was performed, and potential parameters were determined by comparing the simulation with experimental results. Simulation soft ware is Cerius2 (Version?4.2) made by MSI. The purpose of performing simulation is to elucidate an adsorption mechanism on the molecule level.     

Self-assembly of block copolymers

Block copolymer (BCP) self-assembly has attracted considerable attention for many decades because it can yield ordered structures in a wide range of morphologies, including spheres, cylinders, bicontinuous structures, lamellae, vesicles, and many other complex or hierarchical assemblies. These aggregates provide potential or practical applications in many fields. The present tutorial review introduces the primary principles of BCP self-assembly in bulk and in solution, by describing experiments, theories, accessible morphologies and morphological transitions, factors affecting the morphology, thermodynamics and kinetics, among others. As one specific example at a more advanced level, BCP vesicles (polymersomes) and their potential applications are discussed in some detail.     

Sodium 1‐Naphthalenesulfonate‐Functionalized Reduced Graphene Oxide Stabilizes Silver Nanoparticles with Lower Cytotoxicity and Long‐Term Antibacterial Activity

Silver nanoparticles (AgNPs) are increasingly used in daily life for their antibacterial properties, but their low stability and high cytotoxicity hamper practical applications. In this work, sodium 1‐naphthalenesulfonate‐functionalized reduced graphene oxide (NA‐rGO) was used as a substrate for AgNPs to produce a AgNP‐NA‐rGO hybrid. This hybrid showed substantially higher antibacterial activity than polyvinyl pyrrolidone(PVP)‐stabilized AgNPs, and the AgNPs on NA‐rGO were more stable than the AgNPs on PVP, resulting in long‐term antibacterial effects. More importantly, this hybrid showed excellent water solubility and low cytotoxicity, suggesting the great potential application as sprayable reduced graphene oxide based antibacterial solutions.     

Phenolic constituents from the heartwood of Artocapus altilis and their tyrosinase inhibitory activity

From the MeOH extract of the heartwood of Artocapus altilis, thirteen phenolic compounds have been isolated, namely curcumin (1), desmethoxycurcumin (2), retrodihydrochalcone (3), apigenin (4), tangeretin (5), nobiletin (6), O-methyldehydrodieugenol (7), dehydrodieugenol (8), beta-hydroxypropiovanillone (9), p-coumaric acid (10), p-hydroxybenzaldehyde (11), vanillin (12), and vanillic acid (13). This is the first report on the presence of these compounds in the heartwood of A. altilis. Compounds 1, 2, and 10 showed more potent tyrosinase inhibitory activities, with IC50 values ranging from 2.3 to 42.0 microM, than the positive control kojic acid (IC50, 44.6 microM). The most active compound, p-coumaric acid (10) (IC50, 2.3 microM), was 22 times more active in tyrosinase inhibitory activity than kojic acid.     

Size dependence of the mechanical properties of ZnO nanobelts

The Young's modulus of ZnO nanobelts was measured using an atomic force microscope following the modulated nanoindentation method. The nanobelts have a rectangular cross-section, with width-to-thickness ratios ranging 1–10 and lengths up to a few millimetres. The Young's modulus of two nanobelts with width-to-thickness ratio of 2.2 and 1.3 was measured at 55 and 108?GPa, respectively, indicating a size dependence of the elastic properties of the nanobelts.     

Influence of imperfect bonding on interface waves guided by piezoelectric/piezomagnetic composites

Interface waves, which can be guided by imperfectly bonded piezoelectric and piezomagnetic half-spaces, are studied. The cases of absorbent and permeable interfaces are discussed in detail. It is shown that imperfection of the interface bonding has significant impact on the existence of interface waves and on their velocities of propagation. Some interface waves present in the case of imperfect bonding vanish when the bonding becomes perfect. The waves that are guided by an imperfect interface are shown to be dispersive, although there is no explicit characteristic length in the structure model. The results obtained show that possible imperfections of interface bonding must be considered in the design and fabrication of piezoelectric/piezomagnetic composites.     

Condensable InP quantum dots solid

Colloidal thioacetic acid-capped InP quantum dots (InP-TAA QDs) and their spin coated-films have been examined in comparison with those of myristic acid-capped InP (InP-MA) QDs. While the QDs are far away from each other in the InP-MA QD films, even in a InP-MA QD film cured at 250 °C, upon thermal annealing a film of InP-TAA QDs at 250 °C, the indium thioacetate groups on the surfaces QDs likely condensed, thus resulting in the QD film that consists of individual and proximally packed InP QDs. The structures of the films of InP-MA QDs or InP-TAA QDs were characterized by means of TEM, XRD, and XPS. The current through the film of InP-TAA QDs cured at 250 °C was about 2–5 orders of magnitude higher than that of the film of InP-MA film annealed by the sample conditions. We, newly in this letter, define this kind of materials architecture as the condensable QDs solid concept.     

Controlled SnO2 nanocrystal growth in SiO2–SnO2 glass‐ceramic monoliths

Crack‐free (100–x) SiO₂–x SnO₂ glass‐ceramic monoliths have been prepared by the sol–gel method obtaining for the first time SnO₂ concentrations of 20% with annealing at 1100 °C. Heat‐treatment resulted in the formation and growth of SnO₂ nanocrystals within the silica matrices. Combined use of Fourier transform–Raman spectroscopy and in situ high‐temperature X‐Ray diffraction shows that SnO₂ particles begin to crystallize in the cassiterite‐type phase at 80 °C and that their average apparent size remains around 7 nm, even after annealing at 1100 °C. Nanocrystal sizes and size distributions determined by low‐wavenumber Raman are in good agreement with those obtained from transmission electron microscopy measurements. Results indicate that the formation and the growth of SnO₂ nanocrystals impose a residual porosity in the silica matrix. Copyright © 2011 John Wiley & Sons, Ltd.     

Robust stability of positive linear systems in Banach spaces

In this paper, we study the stability radii of positive linear systems with delays with respect to various classes of perturbations in infinite dimensional spaces. It is shown that the positive, real and complex stability radii coincide. Moreover, explicit formulas are derived for these stability radii and illustrated by a simple example.     

The Robustness of Strong Stability of Positive Homogeneous Difference Systems Under Parameter Perturbations

In this article, we study the robustness of strong stability of the homogeneous difference systems via the concept of strong stability radii: complex, real and positive radii under parameter perturbations. We also show that in the case of positive systems, these radii coincide and can be computed by a simple formula. The results generalize those obtained in [5 B.T. Anh and D.D.X. Thanh ( 2008 ). The robustness of strong stability of positive homogeneous difference equations . J. Appl. Math. Article ID 124269; doi : 10 . 1155/2008/124269  [Google Scholar]].