Hierarchical organization of perylene bisimides and polyoxometalates for photo-assisted water oxidation

The oxygen in Earth\u2019s atmosphere is there primarily because of water oxidation performed by photosynthetic organisms using solar light and one specialized protein complex, photosystem II (PSII). High-resolution imaging of the PSII \u2018core\u2019 complex shows the ideal co-localization of multi-chromophore light-harvesting antennas with the functional reaction centre. Man-made systems are still far from replicating the complexity of PSII, as the majority of PSII mimetics have been limited to photocatalytic dyads based on a 1:1 ratio of a light absorber, generally a Ru\u2013polypyridine complex, with a water oxidation catalyst. Here we report the self-assembly of multi-perylene-bisimide chromophores (PBI) shaped to function by interaction with a polyoxometalate water-oxidation catalyst (Ru4POM). The resulting [PBI]5Ru4POM complex shows a robust amphiphilic structure and dynamic aggregation into large two-dimensional paracrystalline domains, a redshifted light-harvesting efficiency of >40% and favourable exciton accumulation, with a peak quantum efficiency using \u2018green\u2019 photons (\u3bb > 500 nm). The modularity of the building blocks and the simplicity of the non-covalent chemistry offer opportunities for innovation in artificial photosynthesis

The handling and fate of spermatophores in Neoentobdella diadema and N-apiocolpos (Monogenea : Capsalidae : Entobdellinae)

Copyright © 2006 Folia ParasitologicaGraham C. Kearn, Ian D. Whittington and Louis Euze

Biopolymers as potential carrier for effervescent reaction based drug delivery system in gastrointestinal condition

Biopolymers are naturally occurring materials formed in nature during the life cycles of organisms. Biopolymers include the polysaccharides, carbohydrates and protein such as cellulose, starch, wool, silk, gelatine and collagen. In recent years, biopolymer-based hydrogels become important area of research in pharmaceutical aspects because of their promising properties in drug delivery system. These properties include low toxicity, biodegradability, stability and renewable nature. Numerous studies have been carried out in order to develop carrier from biopolymers with better controlled release properties. This is important to ensure precisely desired concentration of drug or essential nutrient absorption into the blood or tissue could be achieved. Among other different approaches, floating system is one of the most convenient, economical, and effective drug delivery system. Floating delivery system could potentially achieve longer retention time of carrier with capsulated bioactive drug or functional nutrients in the gastrointestinal tract. The floating behaviour of carrier could be induced by effervescent reactions. Effervescent reaction occurs between acidic gastric content and pore forming agent such as carbonates or bicarbonates salts incorporated into the carrier. This chapter discusses some of the use of biopolymers in drug delivery systems for effervescent reaction in gastrointestinal tract

Upper limit on the diffuse flux of ultrahigh energy tau neutrinos from the Pierre Auger Observatory

The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau neutrinos that interact in Earth’s crust. Tau leptons from charged-current interactions can emerge and decay in the atmosphere to produce a nearly horizontal shower with a significant electromagnetic component. The data collected between 1 January 2004 and 31 August 2007 are used to place an upper limit on the diffuse flux of at EeV energies. Assuming an E2 differential energy spectrum the limit set at 90% C.L. is E2 dN=dE < 1:3 107 GeV cm2 s1 sr1 in the energy range 2 1017 eV<E < 2 1019 eV