Synthesis and blending behavior of an oligoarylenevinylene. Design towards processable materials for LED applications

A bisstyrenebenzene with improved solubility can be obtained by a lateral phenyl substituent on the phenylene ring. The phenyl substituted bisstyrenebenzene (PBSB) was synthesized by Pd-catalyzed coupling of 2,5-dibromobiphenyl and styrene. PBSB exhibits blue fluorescence in solution. Blends of PBSB and polystyrene or polycarbonate are homogeneous over a wide concentration range of PBSB, based on differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results were compared with the blending behavior of unsubstituted bisstyrenebenzene.     

Sensitivity of trust-region algorithms to their parameters

In this paper, we examine the sensitivity of trust-region algorithms on the parameters related to the step acceptance and update of the trust region. We show, in the context of unconstrained programming, that the numerical efficiency of these algorithms can easily be improved by choosing appropriate parameters. Recommended ranges of values for these parameters are exhibited on the basis of extensive numerical tests. MSC classification: 65K05, 90C26, 90C30     

Use of chemiluminescence to the study of photostability of automotive coatings

Chemiluminescence (CL) imaging has been used to study the photodegradation of two automotive coatings, a melamine-crosslinked acrylic resin and an acrylic Polyurethane, as a function of artificial weathering time. Characteristics of the CL emission from coatings, the influence of light stabilizers and different types of sample were studied. The results indicate that the method is highly sensitive and can be used to measure photodegradation in unstabilized and stabilized coatings after only 48 h and 100–200 h of exposure, respectively. Measurements can be carried out on free clearcoats or on clearcoats applied on metallic panels. It is also possible to assess the degradation of individual layers in multiple-layer coating systems. Extrapolation to the failure time of coatings by CL is not yet achievable, but results show that the technique is useful for rapidly screening the relative performance of new coating formulations or light stabilizers added to clearcoats.     

Homoclinics and chaotic behaviour for perturbed second order systems

This paper deals with perturbed dynamical systems of the form: $ - \ddot u + u = \nabla V\left( u \right) + \varepsilon \nabla _u W\left( {t,u} \right)$ where u(t)∈Rⁿ(n?1). By means of a variational approach the existence of multibump homoclinics is proved under general assumptions on the Melnikov function. As a particular case, if (W; u) is T-periodic, the existence of approximate and complete Bernoulli shift structures is proved. An application to partial differential equations is also given.     

Analysis of benzophenone and 4-methylbenzophenone in breakfast cereals using ultrasonic extraction in combination with gas chromatography-tandem mass spectrometry (GC-MS)

Benzophenone (BP) and 4-methylbenzophenone (4MBP) are photo-initiators that are generally used to cure ink on carton boards.In this contribution, a fast and reliable method for the determination of BP and 4MBP in breakfast cereals is described. The sample was extracted ultrasonically using a mixture of dichloromethane and acetonitrile (1:1), followed by a clean-up of the extract using solid phase extraction with a silica cartridge. Finally, the extract was analysed by GC-MSⁿ. Benzophenone-d₁₀ was used as internal standard. The presented method is validated in terms of linearity, recovery, repeatability and intra-laboratory reproducibility, specificity, limit of detection and limit of quantification. In conclusion, this method is able to detect both BP and 4MBP at very low concentrations (LOD = 2 μg kg⁻¹) in breakfast cereals.     

The changing of the guard: Molecular diversity and rapid evolution of β-defensins

Summary Defensins are small cationic peptides involved in innate immunity and are components of the first line of defence against invading pathogens. β-defensins are a subgroup of the defensin family that display a particular cysteine spacing and pattern of intramolecular bonding. These molecules are produced mostly by epithelia lining exposed surfaces and appear to have both antimicrobial and cell signalling functions. The unusually high degree of sequence variation in the mature peptide produced by the paralogous and in some cases orthologous genes implies extensive specialisation and species specific adaptation. Here we review recent functional data that are an important addition to our knowledge of the innate immune response and novel antibiotic design. We also consider the organisation and evolution of the genomic loci harbouring these genes where radical and rapid changes in β-defensin sequences have been shown to result from the interplay of both positive and negative selection. Consequently these genes provide some unusually clear glimpses of the processes of duplication and specialisation that have shaped the mammalian genome.     

IFF YOU WANT ME,I DON'T WANT YOU

The usual assumption in models of asymmetric information is that I know my attributes and you do not. But sometimes the asymmetry seems to be reversed: You (a woman, a firm) know better than I (a man, a job applicant) my market value. This may result in a dilemma because equilibrium strategies may be described by the title of this paper. (Iff means: if and only if.) The result resembles the “No-Trade-Theorem” of Milgrom and Stokey (1982) Milgrom, P. and Stokey, N. 1982. Informaiton, trade and common knowledge. Journal of Economic Theory, 26: 17–27. [Crossref], [Web of Science ®] , [Google Scholar] but cannot be derived from it.     

Hydridosilazanes hydrolysis-condensation reactions studied by <Superscript>1</Superscript>H and <Superscript>29</Superscript>Si liquid NMR spectroscopy

Hydridosilazane compounds containing Si–N and Si–H bonds can be used as precursors of SiO_x materials. The hydrolysis-condensation reactions of tetramethyldisilazane, as a polyhydridosilazane model compound, were investigated by ¹H and ²⁹Si liquid NMR spectroscopy. These reactions were carried out at room temperature for up to 120 min in presence of water. The identified products are short linear siloxane species (hydride terminated polydimethylsiloxanes M^HD_xM^H) and cyclosiloxanes. Silicon hydride persistence in the reactional mixture suggested that silazane group is more sensitive to hydrolysis reaction than silicon hydride group. Moreover, additional experiments evidenced that the low steric hindrance of the silicon hydride influences the silazane hydrolysis kinetic. Hence the presence of ammonia released during silazane hydrolysis reaction was demonstrated to be a catalyst of the silicon hydride hydrolysis reaction.