The influence of β-FeOOH nanorods on the thermal stability of poly(methyl methacrylate)

Colloidal dispersions consisting of β-FeOOH nanorods with three different aspect ratios (4, 75 and 120) were synthesized using thermal hydrolysis of FeCl₃ solutions. After surface modification with oleic acid, the β-FeOOH nanorods were incorporated in poly(methyl methacrylate). Transmission electron microscopy and X-ray diffraction were applied for structural characterization of the β-FeOOH nanorods. The influence of inorganic phase on the thermal properties of PMMA matrix was studied using thermogravimetry and differential scanning calorimetry. Improvement of the thermal stability and increase of the glass transition temperature were found with the increase of content of inorganic phase and the increase of aspect ratio.     

Investigation of the molybdate(II)-3-hydroxyflavone complex

Summary Investigations on the composition of the molybdate(II)-3-hydroxyflavone complex and its stability constant have been carried out in 70% ethanolic solutions at room temperature (20°C), in the presence of a buffer atpH 6.30±0.05 and ionic strength 0.015. It has been found that a complex [MoO₃(C₁₅H₉O₃) ₂ ^2– ] whose stability constant ranges from 15.13 atpH 6.25 to 13.02 atpH 7.00 is formed. Conditions are given for the determination of 3-hydroxyflavone by means of the reaction of complex formation in 50% ethanol atpH 6.60±0.05 and an ionic strength of 0.0225.

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Untersuchung des Molybdat(II)-3-hydroxyflavon-Komplexes

Zusammenfassung Die Untersuchungen der Zusammensetzung des Komplexes und seiner Stabilitätskonstante wurden in 70% Ethanol, bei Raumtemperatur (20°C), in Anwesenheit von Puffer beipH=6.30±0.05 und der Ionenstärke 0.015 ausgeführt. Es wird der Komplex [MoO₃(C₁₅H₉O₃) ₂ ^2– ] gebildet, die Stabilitätskonstanten reichen von 15.13 beipH 6.25 bis zu 13.02 beipH 7.00. Es wurden die Bedingungen zur quantitativen Bestimmung von 3-Hydroxyflavon mittels des Molybdenkomplexes in 50% Ethanol, beipH=6.60±0.05 und der Ionenstärke 0.0225 ermittelt.

     

Synthesis of copolymer brushes endowed with adhesion to stainless steel surfaces and antibacterial properties by controlled nitroxide-mediated radical polymerization

Novel copolymer brushes have been synthesized by a two-step "grafting from" method that consists of the electrografting of poly(2-phenyl-2-(2,2,6,6-tetramethyl-piperidin-1-yloxy)-ethylacrylate) onto stainless steel, followed by the nitroxide-mediated radical polymerization of 2-(dimethylamino ethyl)acrylate and styrene or n-butyl acrylate, initiated from the electrografted polyacrylate chains. The grafted copolymers were quaternized in order to endow them with antibacterial properties. Peeling tests have confirmed the strong adhesion of the grafted copolymer onto the stainless steel substrate. Quartz crystal microbalance experiments have proven that fibrinogen adhesion is lower on the hydrophilic quaternized films compared to the nonionic counterpart. Such quaternized copolymers exhibit significant antibacterial activity against the Gram-positive bacteria S. aureus and the Gram-negative bacteria E. coli.     

The sorption of anthracene onto goethite and kaolinite in the presence of some benzene carboxylic acids

The uptake of anthracene from dilute aqueous solutions onto goethite and kaolinite was investigated at 25 degrees C, first in the absence and then in the presence of three benzene carboxylic acids: phthalic acid (benzene-1,2-dicarboxylic acid), trimesic acid (-1,3,5-), and mellitic acid (-1,2,3,4,5,6-). Carboxylic acid concentrations were 0.20, 0.10, and 0.05 mM. Anthracene (0.20 microM) did not adsorb strongly onto the pure mineral surfaces, but in the presence of phthalic acid a substantial increase in anthracene uptake was observed, particularly for the goethite systems. Trimesic and mellitic acids did not enhance anthracene uptake. Phthalate and proton adsorption data have been used to model phthalate adsorption onto the mineral surfaces using an extended constant capacitance surface complexation model. This model was then successfully adapted to account for the observed increase in anthracene uptake, where anthracene molecules were assumed to interact with adsorbed phthalate. We propose that the enhancement of anthracene adsorption in the presence of phthalic acid is due to an increase in the hydrophobicity of the mineral surface once phthalic acid molecules adsorb. The same effect was not observed for the other benzene carboxylates because of their greater polarity.     

Search for emission of nucleons and nucleon pairs following muon capture in selected light nuclei

Preliminary results of measurements of proton energy spectra and search for coincidentp, n pair emission following negative muon capture in¹²C,¹⁶O,²⁷Al are given. A very clear signal for proton emission is found, which can be exploited in future detailed studies.Presented at the symposium Mesons and Light Nuclei, Bechyn, Czechoslovakia, May 27–June 1, 1985.This work was supported in part by the U.S. National Science Foundation, grant 83-10044-A 2, the German Bundesministerium für Forschung und Technologie, the International Buero Julich, and the Swiss National Science Foundation.     

On the convergence order of accelerated root iterations

Summary A Gauss-Seidel procedure for accelerating the convergence of the generalized method of the root iterations type of the (k+2)-th order (kN) for finding polynomial complex zeros, given in [7], is considered in this paper. It is shown that theR-order of convergence of the accelerated method is at leastk+1+ _n (k), where _n (k)>1 is the unique positive root of the equation ⁿ --k-1 = 0 andn is the degree of the polynomial. The examples of algebraic equations in ordinary and circular arithmetic are given.     

On some iteration functions for the simultaneous computation of multiple complex polynomial zeros

Second order methods for simultaneous approximation of multiple complex zeros of a polynomial are presented. Convergence analysis of new iteration formulas and an efficient criterion for the choice of the appropriate value of a root are discussed. A numerical example is given which demonstrates the effectiveness of the presented methods.     

Room temperature single-photon sources based on single colloidal nanocrystals in microcavities

Direct lithography of resist blends, embedding semiconductor colloidal nanocrystals (NCs) is an innovative way to achieve nanopositioning of NCs in quantum-confined optical resonators. In this work, we show a new appealing approach for the fabrication of single-photon sources operating at room temperature by localizing semiconductor colloidal NCs into vertical planar microcavities with lithographic techniques.     

Bi-hybrid coatings: polyaniline-montmorillonite filler in organic-inorganic polymer matrix

A bi-hybrid composite is represented by an organic-inorganic (O-I) filler dispersed in an O-I matrix. Polyaniline-montmorillonite, as a nanocomposite filler, was synthesised by two independent processes: (1) montmorillonite was surface-modified with a conducting polymer, polyaniline, during the in-situ oxidation of aniline or (2) montmorillonite was pre-treated with aniline, then the aniline was polymerised and the polyaniline subsequently produced penetrated the montmorillonite structure. The organic-inorganic polymer matrix was formed in two independent steps: (1) inorganic building units were formed in situ by the sol-gel process, (2) followed by organic polymeric matrix formation by polyaddition reactions of epoxy groups with amines. Polyaniline-montmorillonite filler was added to the reaction system between these two steps, i.e. when the inorganic structures of the O-I matrix have already been formed but prior to formation of the organic polymeric matrix. Two different O-I matrices were prepared from functionalised organosilicon precursors and oligomeric amines. 3-[(Glycidyloxy)propyl]trimethoxysilane reacted with α,ω-oligo(propylene oxide) diamine and diethoxy[3-(glycidyloxy)propyl]-methylsilane reacted with α,ω-oligo(propylene oxide) triamine. The resulting bi-hybrid coatings, the O-I filler dispersed in the O-I matrix, were characterised by atomic-force and optical microscopies, and also by tensile tests. The filler composition affected both the mechanical and surface properties of the coatings.