Reversible Photorheology in Solutions of Cetyltrimethylammonium Bromide, Salicylic Acid, and trans-2,4,4 '-Trihydroxychalcone

We show photorheology in aqueous solutions of weakly entangled wormlike micelles prepared with cetyltrimethylammonium bromide (CTAB), salicylic acid (HSal), and dilute amounts of the photochromic multistate compound trans-2,4,4'-trihydroxychalcone (Ct). Different chemical species of Ct are associated with different colorations and propensities to reside within or outside CTAB micelles. A light-induced transfer between the intra- and intermicellar space is used to alter the mean length of wormlike micelles and hence the rheological properties of the fluid, studied in steady-state shear Bow and in dynamic rheological measurements. Light-induced changes of fluid rheology are reversible by a the relaxation process. at relaxation rates which depend on pH and which are consistent with photochromic reversion rates measured by UV-vis absorption spectroscopy. Parameterizing viscoelostic rheological states by their effective relaxation time tau(c) and corresponding response modulus G(c), we find the light and dark states of the system to fall onto a characteristic state curve defined by comparable experiments conducted without photosensitive components. These reference experiments were prepared with the same concentration of CTAB, but different concentrations of HSal or sodium salicylote (NaSal), and tested at different temperatures.

New heterogeneous catalysts for trans-esterification of triglycerides

This paper describes preliminary work done towards the development of new metallic heterogeneous catalysts to be used in the transesterification reaction of triglycerides, which is of considerable interest in the production of biodiesel. Biodiesel, is a mixture of mono-alkyl esters of fatty acids, and is currently manufactured by transesterification of triglycerides with methanol using NaOH or KOH as liquid base catalyst. Catalysts as such are corrosive to the equipment, and as these catalysts are in liquid phase must be neutralized after the completion of the reaction, typically using HCl, thus producing salt streams. Moreover, due to the presence of free fatty acids it reacts to form soaps as unwanted by-products, hence requiring more expensive separation processes. Therefore, there is a great need on the development of industrial processes for biodiesel production using solid acid catalysts. The key benefit of using solid acid catalysts is that no polluting by-products are formed and the catalysts do not have to be removed since they do not mix with the biodiesel product.

Processos de trans-nacionalização da linguagem publicitária. Não basta colocar as campanhas publicitárias internacionais no ar. É necessário que os conceitos criativos possam “voar”.

Este artigo analisa a questão da trans-nacionalização da linguagem publicitária e da sua eficácia. O mundo actual está num processo de grande transformação social e dele emerge um novo paradigma da comunicação comercial. A trans-nacionalização da linguagem publicitária põe em marcha dois processos paralelos. Por um lado, contribui para uma certa homogeneização cultural (visível sobretudo nos conceitos globais e na utilização do inglês como língua de ancoragem de sentido universal) e para a emergência de valores sociais de cariz global, porque desterritorizados. Outro processo é o da diversificação cultural, com valores diferenciados (que nascem da apropriação, transformação e re-contextualização de significações) que passam a operar como códigos, mais ou menos fechados, de comunidades sociais, de toda a espécie, que em torno deles se estruturam. Essa ocorrência, parece ser mais frequente entre as novas gerações (mas não necessariamente) e estas também usam, normalmente, certas marcas e certos objectos de consumo, quase sempre ligados ao segmento da moda, que se transformam em símbolos de pertença da tribo. A mudança de paradigma faz realçar o factor criatividade como garante da eficácia publicitária. Uma das principais consequências desta mudança de paradigma é que as marcas deixarão de entrar facilmente na casa do consumidor e na sua mente através de uma estratégia cerrada de “bombardeamento” e a linguagem publicitária deverá retornar aos valores sociais e culturais importantes, oferecendo espectáculo, sonho, significado e relação. Porque, afinal, não basta colocar as campanhas publicitárias internacionais no ar, é necessário que os conceitos criativos possam “voar”.

Acylated cyanoimido-complexes trans-[Mo(NCN){NCN(O)R}(DPPE)(2)]Cl and their reactons with electrophiles: Chemical, electrochemical and theoretical study

Treatment of a dichloromethane solution of trans-[Mo(NCN){NCNC(O)R}(dppe)(2)]Cl [R = Me (1a), Et (1b)] (dppe = Ph2PCH2CH2PPh2) with HBF4, [Et3O][BF4] or EtC(O)Cl gives trans-[Mo(NCN)Cl-(dppe)(2)]X [X = BF4 (2a) or Cl (2b)] and the corresponding acylcyanamides NCN(R')C(O)Et (R' = H, Et or C(O)Et). X-ray diffraction analysis of 2a (X = BF4) reveals a multiple-bond coordination of the cyanoimide ligand. Compounds 1 convert to the bis(cyanoimide) trans-[Mo(NCN)(2)(dppe)(2)] complex upon reaction with an excess of NaOMe (with formation of the respective ester). In an aprotic medium and at a Pt electrode, compounds 1 (R = Me, Et or Ph) undergo a cathodically induced isomerization. Full quantitative kinetic analysis of the voltammetric behaviour is presented and allows the determination of the first-order rate constants and the equilibrium constant of the trans to cis isomerization reaction. The mechanisms of electrophilic addition (protonation) to complexes 1 and the precursor trans[Mo(NCN)(2)(dppe)(2)], as well as the electronic structures, nature of the coordination bonds and electrochemical behaviour of these species are investigated in detail by theoretical methods which indicate that the most probable sites of the proton attack are the oxygen atom of the acyl group and the terminal nitrogen atom, respectively.