Hedonism and the experience machine

Money isn’t everything, so what is? Many government leaders, social policy theorists, and members of the general public have a ready answer: happiness. This paper examines an opposing view due to Robert Nozick, which centres on his experience-machine thought experiment. Despite the example's influence among philosophers, the argument behind it is riddled with difficulties. Dropping the example allows us to re-version Nozick's argument in a way that makes it far more forceful - and less dependent on people's often divergent intutions about the experience machine

Lichenometric dating (lichenometry) and the biology of the lichen genus rhizocarpon:challenges and future directions

Lichenometric dating (lichenometry) involves the use of lichen measurements to estimate the age of exposure of various substrata. Because of low radial growth rates and considerable longevity, species of the crustose lichen genus Rhizocarpon have been the most useful in lichenometry. The primary assumption of lichenometry is that colonization, growth and mortality of Rhizocarpon are similar on surfaces of known and unknown age so that the largest thalli present on the respective faces are of comparable age. This review describes the current state of knowledge regarding the biology of Rhizocarpon and considers two main questions: (1) to what extent does existing knowledge support this assumption; and (2) what further biological observations would be useful both to test its validity and to improve the accuracy of lichenometric dates? A review of the Rhizocarpon literature identified gaps in knowledge regarding early development, the growth rate/size curve, mortality, regeneration, competitive effects, colonization, and succession on rock surfaces. The data suggest that these processes may not be comparable on different rock surfaces, especially in regions where growth rates and thallus turnover are high. In addition, several variables could differ between rock surfaces and influence maximum thallus size, including rate and timing of colonization, radial growth rates, environmental differences, thallus fusion, allelopathy, thallus mortality, colonization and competition. Comparative measurements of these variables on surfaces of known and unknown age may help to determine whether the basic assumptions of lichenometry are valid. Ultimately, it may be possible to take these differences into account when interpreting estimated dates

Research trends in combinatorial optimization

Acknowledgments This work has been partially funded by the Spanish Ministry of Science, Innovation, and Universities through the project COGDRIVE (DPI2017-86915-C3-3-R). In this context, we would also like to thank the Karlsruhe Institute of Technology. Open access funding enabled and organized by Projekt DEAL.Peer reviewedPublisher PD

Early interactions between arbuscular mycorrhizal fungi and Frankia during colonisation and root nodulation of Alnus glutinosa

Glasshouse experiments showed significant differences in early interactions of Alnus glutinosa with five different arbuscular mycorrhizal species and Frankia. Thirty and 60 days after inoculation of roots with AMF alone, colonisation was highest with Glomus hoi and G. mosseae followed by Gigaspora rosea. Lowest colonisation was with Acaulospora scrobiculata and Scutellospora castanea. In associations with AMF resulting in relatively low colonisation, e.g. S. castanea, plant biomass after 60 days was higher than in un-inoculated controls but when inoculated with Frankia also was equal to controls. In contrast, the biomass of plants with high levels of AMF colonisation e.g. with G. hoi, was equal to the controls when alone but was lower in dual symbiosis with Frankia. This effect was particularly marked 30 days after inoculation. There was also a depressive effect of nodulation on plant biomass 30 days after dual inoculation that was less apparent after 60 days. This effect was most marked for AMF giving rise to the highest levels of colonisation (G. hoi and Gi. rosea). The data suggest that in dual inoculated alder seedlings, inhibitory effects on early growth can result, possibly from competition with micro-symbionts for resources such as photosynthates. However, effects may only be temporary, to be relieved as seedlings develop a larger shoot system with greater photosynthetic capacity