Why Gratzel’s cell works so well

In Gratzel’s cell, the electrons injected by the photo-excitation of dye molecules, anchored to a mesoporous TiO₂ film, efficiently diffuse to the back contact achieving solar energy conversion at efficiencies exceeding 10%. The mesoporous TiO₂ surface constituted of randomly arranged nanocrystallites with a roughness factor of the order 1000 is heavily populated with traps, defects and adsorbed species which act as recombination centers. Nevertheless, the cell functions, mitigating recombination expected to occur via the interaction electrons at the surface. Evidence based mainly on 1/f noise measurements is presented to show that dye bonded to the TiO₂ surface passivates recombination centers. Furthermore the suppression of trapping-detrapping events at the surface increases the diffusion coefficient of the electrons through the nanocrystalline matrix facilitating electron transport to the back contact. The Gratzel cell is also unique, none of the high bandgap oxide materials other than TiO₂ yield energy conversion and quantum efficiencies as high as that of the cells based on TiO₂. 1/f noise measurements also reveal a distinct difference between TiO₂ and ZnO mesoporous films suggesting that the films made from the latter material are more intensely populated with surface states that mediate recombination.     

Why do so many arts and social scientists have huge difficulties accepting (evolutionary)biologically based opinions for gender differences

The contribution deals with the wide-spread rejection of (evolutionary) biological founded statements concerning sex differences by social sciences and arts, which are not based on objective objections, but are ideologically justified. The starting point therefore is to be seen in the justified critique of the biological legitimized racism and sexism in the sixties and seventies of the last century. The continuation of this rejecting position, though the modern biology has changed itself essentially, can be explained psychologically by Festinger's "Theory of Cognitive Dissonance".     

The under-financing of protected areas in the Congo Basin: so many parks and so little willingness-to-pay

Protected areas in the Congo Basin cover approximately 6% of the landscape, and several international NGOs are proposing substantial additions to the present network of parks and reserves. Yet, chronic under-funding has long precluded effective management of most parks and reserves resulting in their progressive ecological impoverishment, and the loss of biodiversity. Furthermore, not only are the indebted nations of the Congo Basin not in a position to contribute significantly to cover the recurring costs of protected area management, the growing opportunity costs of setting aside protected areas is increasing the incentives to local communities and national governments to 'illegally' exploit economically valuable resources within parks and reserves. If the global value of the biodiversity contained within the Congo Basin is considered worth preserving then donors and international NGOs must work with national governments to reach consensus on an optimal protected area network that (a) contains a representative assemblage of forest species; (b) is composed of forest blocks that are sufficiently large, intact, and likely to persist; (c) contains zones of active speciation (e.g. ecotones), and (d) can expect to receive sufficient long-term financial support to ensure effective management. Given the 'need to eat today' reality of economies in the Congo Basin, the international community must decide to shoulder most of the costs of conservation of globally important biodiversity. If donors continue to under-finance protected areas rather than make the hard choices associated with prioritizing protected area spending then most if not all protected areas within the Congo Basin will continue to exhibit reductions in the biomass of individual species, and risk the extirpation or extinction of large, slow reproducing species, and rare endemics.     

The discovery of penicillin: so many get it wrong

Alexander Fleming discovered penicillin in September 1928, the most likely date being Monday 3 September on his return from holiday in Suffolk. This discovery has attracted more myths and misinformation than probably any other in the history of medicine.     

Why genetic investigation of psychiatric disorders is so difficult

Genetic investigations of psychiatric disease have historically relied on subjectively assessed disease diagnoses to define phenotypes. Recent developments in several areas have provided various new approaches to behavioral disorder phenotyping that promise to advance our understanding of the genetic and environmental etiologies of these traits. Such developments include re-evaluation of the boundaries between different psychiatric categories, implementation of quantitative neurobiological assessments that may serve as endophenotypes, generation of increasingly sophisticated animal behavioral models, and investigation of explicit environmental covariates. At the same time, movement toward large-scale, collaborative efforts is increasing the effectiveness of traditional genetic mapping approaches.     

Why many biological parameters are connected by power dependence

It has long been recognized that interaction of different biosystem parameters often shows a power pattern. A classical example of such an interaction is that of oxygen consumption and the total body weight. Nevertheless, power law has not so far got a valid biological motivation. The authors show that in a number of cases power relationship between parameters can be explained by their dependence on the common governing centre. The possibility of such an interpretation is regarded in terms of “Rubner's law”.