The effect of macromolecular architecture in nanomaterials: a comparison of site isolation in porphyrin core dendrimers and their isomeric linear analogues

The influence of macromolecular architecture on the physical properties of polymeric materials has been studied by comparing poly(benzyl ether) dendrons with their exact linear analogues. The results clearly confirm the anticipation that dendrimers are unique when compared to other architectures. Physical properties, from hydrodynamic volume to crystallinity, were shown to be different, and in a comparative study of core encapsulation in macromolecules of different architecture, energy transduction from the polymer backbone to a porphyrin core was shown to be different for dendrimers as compared to that of isomeric four- or eight-arm star polymers. Fluorescence excitation revealed strong, morphology dependent intramolecular energy transfer in the three macromolecular isomers investigated. Even at high generations, the dendrimers exhibited the most efficient energy transfer, thereby indicating that the dendritic architecture affords superior site isolation to the central porphyrin it surrounds.     

Swimming in an inviscid fluid

We present a set of equations governing the motion of a body due to prescribed shape changes in an inviscid, planar fluid with nonzero vorticity. The derived equations, when neglecting vorticity, reduce to the model developed in Kanso et al. (J Nonlinear Sci 15:255–289, 2005) for swimming in potential flow, and are also consistent with the models developed in Borisov et al. (J Math Phys 48:1–9, 2007), Kanso and Oskouei (J Fluid Mech 800:77–94, 2008), Shasikanth et al. (Phys Fluids 14(3):1214–1227, 2002) for a rigid body interacting dynamically with point vortices. The effects of cyclic shape changes and the presence of vorticity on the locomotion of a submerged body are discussed through examples.     

Evaluation of the mechanical properties of high-strength cement paste at elevated temperatures using metakaolin

Journal of Thermal Analysis and Calorimetry - This paper presents a wide experimental study, in which it evaluates the performance of high-strength paste exposed to elevated temperatures up to...     

HPLC Method for Chiral Separation and Quantification of Antidepressant Citalopram and Its Precursor Citadiol

HPLC method enabling chiral separation and determination of citalopram (CIT), a widely used antidepressant, and its synthetic precursor citadiol in one analysis was developed and validated. Moreover, supercritical fluid chromatography was also tested and was proved to be less effective for this separation purpose. The optimized HPLC system was composed of Chiralcel OD-H column and n-hexane/propane-2-ol/triethylamine 96/4/0.1 (v/v/v) as mobile phase, column temperature 25 °C, flow rate 1.0 mL min^?1, UV detection at 250 nm. The effects of amount of propane-2-ol, triethylamine addition, and temperature on enantioselectivity and resolution of the enantiomers were evaluated. The method was found to be suitable for determination of the enantiomeric purity of CIT in bulk drugs. Enantiomers of CIT were determined in two commercially available pharmaceuticals.