Surface analysis of particulates from laboratory hood exhaust manifold

Particulate samples collected from a laboratory ventilation manifold during routine maintenance were analyzed to determine if particulate composition had changed as a result of changes in the laboratory's atmosphere. This ventilation manifold exhausts more than 100 fume hoods. The particulate samples were analyzed using static secondary ion mass spectrometry (SIMS). The negative SIMS spectra showed abundant Cl^?, NO₃^?, and HSO₄^?, consistent with the use of mineral acids in the laboratory. Cluster anions containing primarily Zn (but also other transition metals) were detected, which signaled corrosion of the manifold's galvanized steel by the volatilized acids. The most abundant ions in the cation SIMS spectra were derived from cyclohexylamine (CHA), which had been used as an antiscaling agent in the facility's boiler. Steam from the boiler, which contained CHA, was used to humidify the building air; this practice stopped in 1997. The abundances of the CHA‐derived ions were significantly lower in the samples collected in 2004 and 2006 than in the 1992 samples, indicating that the CHA is being slowly depleted. Changes in the relative abundances suggest exponential depletion from the manifold with rate constants that are on the order of 0.01 to 0.04 month^?1. Published in 2007 John Wiley & Sons, Ltd.     

Global Entanglement Measures and Quantum Phase Transitions in the 1D J 1? J 2 Model

We have analyzed the behavior of multipartite global entanglement and average bipartite concurrence for the sign of quantum phase transitions in the frustrated J ₁−J ₂ model by using exact diagonalization technique for a chain of 12 qubits. It is found that although the magnitude of two classes of the measures show opposite trends the absolute value of their derivatives show similar structure near critical points.     

On a multivariable extension of the Humbert polynomials

In this paper, we present a multivariable extension of the Humbert polynomials, which is motivated by the Chan-Chyan-Srivastava multivariable polynomials, the multivariable extension of the familiar Lagrange-Hermite polynomials and Erkus-Srivastava multivariable polynomials. We derive various families of multilinear and mixed multilateral generating functions for these polynomials. Other miscellaneous properties of these multivariable polynomials are also discussed. Some special cases of the results presented in this study are also indicated.     

Effects of pH, concentration and temperature on radionuclides sorption onto polyhydroxyethyl methacrylate-expanded perlite composite

Poly (hydroxyethylmethacrylate-expanded perlite) [P(HEMA-EP)], was synthesized and its adsorptive features were investigated for natural radionuclides (TI⁺, Ra²⁺, Bi³⁺, Ac³⁺ and Pb²⁺) in aqueous media at differing initial pH, initial radionuclides concentration and adsorption thermodynamics. The amounts of natural radionuclides at equilibrium were determined by gamma spectrometry. The Langmuir adsorption capacities (X_L) were found to be in the order of ²¹²Pb (0.4 MBq kg^?1) > ²²⁸Ac and ²⁰⁸Tl (0.3 MBq kg^?1) > ²²⁶Ra and ²¹²Bi (0.2 MBq kg^?1). These findings indicated that P(HEMA-EP) adsorbed natural radionuclides with high affinity. It was also demonstrated that the adsorption mechanism was spontaneous (ΔG < 0), the process was exothermic (ΔH < 0) thus increasing entropy (ΔS > 0). The composite was reused for four more times after regeneration without any detectable changes either in its structure or adsorptive capability.     

Efficient immobilization and patterning of live bacterial cells

A monolayer of live bacterial cells has been patterned onto substrates through the interaction between CFA/I fimbriae and the corresponding antibody. Patterns of live bacteria have been prepared with cellular resolution on silicon and gold substrates for Salmonella enterica serovar Typhimurium as a model with high specificity and efficiency. The immobilized cells are capable of dividing in growth medium to form a self-sustaining bacterial monolayer on the patterned areas. Interestingly, the immobilized cells can alter their orientation on the substrate, from lying-down to standing-up, as a response to the cell density increase during incubation. This method was successfully used to sort a targeted bacterial species from a mixed culture within 2 h.     

The synthesis of two new isonitrosoacetophenone derivatives and investigation of their Ni(II), Co(II), Cu(II), and Zr(IV) complexes

In the present study, two new ligands, 4-chlorobenzal-azino-isonitrosoacetophenone (L₁), 4-methylbenzal-azino-isonitrosoacetophenone (L₂) and their metal complexes were synthesized using acetophenone as a starting material. The coloured complexes were prepared by the addition of chloride salts of Ni(II), Co(II), Cu(II) and Zr(IV) ions to a solution of ligands. In conclusion, the structures of the obtained ligands and their complexes were characterized by FT-IR, and ¹H NMR spectra, AAS (atomic absorption spectrum) analysis, magnetic susceptibilities as well as elemental analysis.     

Dendritic structures of poly(ethylene glycol) on silicon nitride and gold surfaces

A hydrophilic silicon nitride surface was grafted with poly(ethylene glycol) monomethyl ether (average formula weight of 5000 Da) in a one-step protocol. The domains of stable dendritic structures of self-assembled monolayer islands on a silicon nitride surface were observed with atomic force microscopy. The moduli of elasticity of these dendritic structures in air and in KCl aqueous solution were compared. The value of the Young's modulus of these structures is reduced by more than 3 orders of magnitude, from approximately 12 GPa measured in air to approximately 5 MPa in KCl solution. This dramatic reduction in elasticity was attributed to the swelling of the dendritic structures in aqueous solution, which was verified by the increased film thickness. These dendritic structures were not stable in the aqueous environment and could be removed by soaking in water for 22 h because of the hydrolysis of the silicate bonds. This fact was confirmed by the reduction of the C1s signal in the X-ray photoelectron spectroscopy experiments. These morphologies are not unique to silicon nitride substrate; similar features were also observed for thiolated poly(ethylene glycol) monomethyl ether molecules absorbed on a gold surface.     

Combining Step-Growth and Chain-Growth Polymerizations in One Pot: Light-Induced Fabrication of Conductive Nanoporous PEDOT-PCL Scaffold

A novel method based on light-induced fabrication of a poly (3,4-ethylenedioxythiophene)-polycaprolactone (PEDOT-PCL) scaffold using phenacyl bromide (PAB) as a single-component photoinitiator is presented. HBr released from the step-growth polymerization of EDOT is utilized as an in situ catalyst for the chain-growth polymerization of ε-caprolactone. Detailed investigations disclose the formation of a self-assembled nanoporous electroconductive scaffold (1.2 mS cm⁻¹). Fluorescence emission spectra of the fabricated scaffold exhibit a mixed solvatochromic behavior, indicating specific interactions between the self-assembled scaffold and solvents with varying polarities, as evidenced by transmission electron microscopy (TEM). Moreover, the same light-induced technique can also be applied for bulk photopolymerization showcasing the versatility and wide-ranging scope of the originated method. In brief, this study introduces a novel approach for light-induced polymerization reactions that is merging step-growth and chain-growth mechanisms. This innovative approach is promising to facilitate in situ polymerization of monomers possessing diverse functionalities.