Selective phosphodiesterase inhibitors: a promising target for cognition enhancement

# The Author(s) 2008. This article is published with open access at Springerlink.com Rationale One of the major complaints most people face during aging is an impairment in cognitive functioning. This has a negative impact on the quality of daily life and is even more prominent in patients suffering from neurodegenerative and psychiatric disorders including Alzheimer’s disease, schizophrenia, and depression. So far, the majority of cognition enhancers are generally targeting one particular neurotransmitter system. However, recently phosphodiesterases (PDEs) have gained increased attention as a potential new target for cognition enhancement. Inhibition of PDEs increases the intracellular availability of the second messengers cGMP and/or cAMP. Objective The aim of this review was to provide an overvie

A comparative study of the effects of constructional elements on the mechanical behaviour of dragonfly wings

Although wings of insects show a large variation in morphology, they are all made from a network of irregular veins interconnected through membranous areas. Depending on their shape, size, and position, wing veins are usually divided into three different groups: longitudinal veins, cross-veins and ambient veins. The veins together with the membrane and some other elements such as spines, nodus and pterostigma can be considered as the wing’s “constructional elements”. In spite of rather extensive literature on dragonfly wing structure, the role of each of these elements in determining the wing’s function remains mostly unknown. As this question is difficult to answer in vivo using biomechanical experiments on actual wings, this study was undertaken to reveal the effects of the constructional elements on the mechanical behaviour of dragonfly wings by applying numerical simulations. An image processing technique was used to develop 12 finite element models of the insect wings with different constructional elements. The mechanical behaviour of these models was then simulated under normal and shear stresses due to tension, bending and torsion. A free vibration analysis was also performed to determine the resonant frequencies and the mode shapes of the models. For the first time, a quantitative comparison was carried out between the mechanical effects selectively caused by different elements. Our results suggest that the complex interactions of veins, membranes and corrugations may considerably affect the dynamic deformation of the insect wings during flight.113122

Petrogenesis and thermal history of the Yulong porphyry copper deposit, Eastern Tibet: insights from U-Pb and U-Th/He dating, and zircon Hf isotope and trace element analysis

The Yulong porphyry copper deposit (6.5 Mt at 0.46 % Cu) in eastern Tibet was formed in a post-collisional setting. New zircon U–Pb and U–Th/He ages, apatite U–Th/He ages and in-situ zircon Hf isotopic and trace element data for the Yulong ore-bearing adakitic porphyries elucidate the thermal history and petrogenesis of the deposit. Zircon U–Pb ages range from from 41.2 Ma to 40.7 Ma, indicating an Eocene formation age. Combined with the zircon U–Th/He age of 37.5 ± 1.2 Ma, results suggest that magmatic-hydrothermal evolution lasted up to 5 m.y. The apatite U–Th/He age of 33.4 ± 0.9 Ma reflects Yulong deposit exhumation during the ~33–30 Ma Tibetan uplift. Moreover, the high εHf(t)-values (7.1 ~ 12.2) zircon yield the highest ΣREE content, higher Y/Hf, lower Ce/Ce* and higher Th/U ratios compared to inherited zircon or magmatic zircon suggesting that the high εHf(t) zircon crystallized from another magma, and that magma mixing probably contributed to the adakitic porphyries at Yulong. In addition, inherited and magmatic zircon with the lowest εHf(t) values (−20.6 ~ −4.4) suggest crustal contamination. The positive zircon εHf(t) values indicate a source in the juvenile arc lower crust. Significantly, the juvenile arc lower crust inherited arc magma characteristics (abundant F, Cl, Cu and high oxidation state), which are now found in the porphyry Cu–Mo deposits