Photomechanical effects in liquid crystal polymer networks prepared with m‐fluoroazobenzene

The photomechanical response and photochemistry of a conventional, unsubstituted azobenzene‐functionalized liquid crystalline polymer network (azo‐LCN) is contrasted to that of an analogous material prepared with meta‐fluorinated azobenzene chromophores. The polydomain azo‐LCN materials exhibit nearly identical thermomechanical and optical properties. Photomechanical characterization indicates that the fluorination of the azobenzene chromophore reduces the deflection of cantilevers composed of the materials by 50%, which spectroscopic analysis reveals is due to a reduction in the ability of this material to isomerize and potentially reorient. This work is further confirmation that the underlying photochemistry of azobenzene is a primary contributor to the generation of photomechanical work in these materials. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 876–882     

Aromatic and Antiaromatic Pathways in Triphyrin(2.1.1) Annelated with Benzo[b]heterocycles

Understanding of the aromatic properties and magnetically induced current densities of highly conjugated chromophores is important when designing molecules with strongly delocalized electronic structure. Linear extension of the triphyrin(2.1.1) skeleton with an annelated benzo[b]heterocycle fragment modifies the aromatic character by extending the electron delocalization pathway. Two-electron reduction leads to an antiaromatic triphyrin(2.1.1) ring and an aromatic benzo[b]heterocycle subunit. Current-density calculations provide detailed information about the observed pathways and their strengths.     

Novel regulation of aflatoxin B1 biosynthesis in Aspergillus flavus by piperonal

The present study investigated its inhibitory role in aflatoxin (AF) biosynthesis. Treating only AFB1- and B2-producing Aspergillus flavus with piperonal completely inhibited AFB1 production with high sclerotial formation, resulting in 20-fold higher AFG2 production. On the other hand, benzodioxole and eugenol suppressed AFB1 production without AFG formation, while methyleugenol showed potent inhibition of AFB1 production with slight production of AFG1. These results indicate that natural products may change aflatoxin biosynthesis, and highlight a novel regulation of AFG2 production by piperonal. It is the first report for chemical regulation on AFG2 production in non-AFG producing-aspergilli.     

Geochemical investigation of alluvial sediments: validation of ICP-OES determination of heavy metals. A case study from the Utrata River Valley (central Poland)

The development and validation of a reliable analytical procedure for the determination of selected metals (Cd, Cr, Cu, Pb, Zn and Mn) in sediments accumulated in the Utrata River (Poland) is described. The aqua regia extraction followed by inductively coupled plasma optical emission spectrometry (ICP-OES) was used for this purpose. The optimized analytical procedure was validated, and adequate quality control actions were implemented in order to provide reliable data. The precision under’ within-laboratory’ reproducibility conditions was estimated from duplicate analysis. Certified reference material (CRM) was used in order to evaluate the accuracy of the results regarding the sewage sludge amended soil CRM 143R. The detection limits for all elements of interest were well-below their content in the investigated sediment samples. The obtained reliable data could be used for assessment of the relationship between human economic activity in the past and the geochemical features of the sediments.