Nanofluid polyurethane/polyurea resins—thin films and clearcoats

Solvent‐free nanofluids with surface functional groups composed of tetraalkylammonium ionic liquid organic salts and isothiocyanate decorating nanosilica cores are reported that exhibit viscous flow and glass transitions. These nanofluids when combined with hexamethylene diisocyanate and isophorone diisocyanate–polypropyleneglycol prepolymers are coated and autocured in humid air to produce thin films and clearcoats. These new resins are characterized thermally and by nanoindentation. Relative to the air‐cured prepolymer control, low nanofluid loading (1–4% w/w) produces increased storage moduli and hardness and decreased loss factors. High loading (8 and 16%) results in softening with increased toughness. While the control exhibited marked viscoelastic recovery, this recovery was largely arrested in the nanocomposite coatings. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3439–3448     

Finding common fixed points of a class of paracontractions

For a suitable set of not necessarily linear operators on a real Hilbert space, such that the set of common fixed points of the operators is nonempty and has an interior point, we construct an asynchronous parallel algorithm that leads to a common fixed point in a finite number of steps. This generalizes a result in [13]. This revised version was published online in June 2006 with corrections to the Cover Date.     

Quantitative liquid chromatographic determination of cefatrizine in serum and urine by fluorescence detection after post-column derivatization

A fast, specific and sensitive high-performance liquid chromatographic procedure for the determination of cefatrizine, an orally active cephalosporin, in serum and urine is proposed. The drug is determined by the internal standard method, using cephradine as the internal standard. The separation is carried out on a reversed-phase column, filled with octadecylsilane chemically bonded microparticles. The eluent is a mixture of acetonitrile with 0.025 M sodium phosphate buffer (pH 7). Quantitation is effected by fluorescence detection of the fluorophores formed after post-column derivatization with fluorescamine in a packed-bed reactor. The chromatographic conditions and the conditions for the post-column derivatization are discussed. The method has been applied to serum and urine samples, which were analysed after deproteinization with trichloroacetic acid and injection of the clear supernatant. The accuracy and reproducibility of the procedure were investigated by the determination of the cefatrizine content in spiked serum and urine samples.     

On partially orderedn-groups

In this paper our chief aim has been to give a definition of positive and negative elements of a partially orderedn-groupG without identity, such that this definition corresponds with the ordinary one if there do exist an identity. Further on we find two necessary and sufficient conditions to conclude about the positivity of an elementa∈G by use of the querelementā ofa. The obtained results are then used to check the law of signs of a fully ordered (n, m)-ring, and to give a starting point of pseudo-valuated (n, m)-rings.     

Thermoanalytical and morphological studies of cross-linked latex films by advanced techniques

In the present report, thermal analysis (TMDSC, DMA, TG, stress-strain analysis), nano-indentation and AFM morphological characterization of cross-linkable latexes, prepared with either a pre-coalescence cross-linker (1,3-butylene glycol dimethacrylate) or post-coalescence cross-linker (adipic dihydrazide) at various levels of cross-linking, were done. The study assesses the effect of type and level of cross-linking on the film formation process through the evolution of mechanical properties and latex morphology. In addition, the final fundamental thermal and mechanical properties, specific end-use properties and latex morphology resulting from the film formation process are reported.     

Value-at-risk prediction using context modeling

In financial market risk measurement, Value-at-Risk (VaR) techniques have proven to be a very useful and popular tool. Unfortunately, most VaR estimation models suffer from major drawbacks: the lognormal (Gaussian) modeling of the returns does not take into account the observed fat tail distribution and the non-stationarity of the financial instruments severely limits the efficiency of the VaR predictions. In this paper, we present a new approach to VaR estimation which is based on ideas from the field of information theory and lossless data compression. More specifically, the technique of context modeling is applied to estimate the VaR by conditioning the probability density function on the present context. Tree-structured vector quantization is applied to partition the multi-dimensional state space of both macroeconomic and microeconomic priors into an increasing but limited number of context classes. Each class can be interpreted as a state of aggregation with its own statistical and dynamic behavior, or as a random walk with its own drift and step size. Results on the US S&P500 index, obtained using several evaluation methods, show the strong potential of this approach and prove that it can be applied successfully for, amongst other useful applications, VaR and volatility prediction. The October 1997 crash is indicated in time. Received 2 September 2000 and Received in final form 12 October 2000     

A sequential iteration algorithm with non-monotoneous behaviour in the method of projections onto convex sets

The method of projections onto convex sets to find a point in the intersection of a finite number of closed convex sets in a Euclidean space, may lead to slow convergence of the constructed sequence when that sequence enters some narrow “corridor” between two or more convex sets. A way to leave such corridor consists in taking a big step at different moments during the iteration, because in that way the monotoneous behaviour that is responsible for the slow convergence may be interrupted. In this paper we present a technique that may introduce interruption of the monotony for a sequential algorithm, but that at the same time guarantees convergence of the constructed sequence to a point in the intersection of the sets. We compare experimentally the behaviour concerning the speed of convergence of the new algorithm with that of an existing monotoneous algorithm.     

Gas-chromatographic determination of camylofine dihydrochloride in tablets and suppositories.

A gas-chromatographic method for the quantitative determination of camylofine dihydrochloride, a spasmolytic agent, is described. The analysis is made on a porous polymer packing material, by determining the 3-methyl-1-butanol formed on alkaline hydrolysis of the drug. The method has been applied to the quantitative determination of the drug in two galenical forms, namely tablets and suppositories, in the presence of papaverine hydrochloride, codeine phosphate, novalgin and aminopyrine.