Comparative life cycle assessment of graphitic carbon nitride synthesis routes

Graphitic carbon nitride (g-C₃N₄) has gained great interest as a visible-light-activated photocatalyst. As an emerging nanomaterial for environmental applications, its competitive performance and environmentally responsible synthesis are critical to its success. A powerful tool for informing material development with reduced environmental impacts is life cycle assessment (LCA). In this study, LCA is used to evaluate the environmental impacts of g-C₃N₄ nanosheet produced via eight existing synthesis routes. The results reveal electricity as the main contributor to the cumulative impacts of all eight g-C₃N₄ syntheses. There are opportunities to reduce energy demand, and consequently the synthesis impacts, by revising synthesis procedures (i.e., removing or reducing time of use of a piece of equipment), optimizing the calcination step (i.e., faster heating rate, lower heating time, lower temperature), and moving to cleaner electricity sources. Further, benchmarking the environmental impacts of g-C₃N₄ nanosheets to a well-established metal-based photocatalyst, titanium dioxide nanoparticles (nano-TiO₂), reveals mixed comparative results. The synthesis method substantially influences the comparative impacts. Considering use-phase benefits of activating g-C₃N₄ with visible wavelength light emitting diodes compared to ultraviolet (UV) wavelengths for nano-TiO₂ results in a 52% energy demand reduction (in kWh). Performance of g-C₃N₄ compared to a high-energy disinfection approach (i.e., conventional UV) reveals an inability to meet drinking water disinfection standards for viral load reduction (4-log reduction) with any mass of g-C₃N₄, given its high embodied resource footprint. This work establishes a foundation to inform and direct g-C₃N₄ nanosheets toward improved sustainable development.     

Synopsis ofGalago species characteristics

At the time of the symposium, “Variability Within the Galagos,” at the 1986 IPS Congress, most participants were still using Hill’s (1953) classification and nomenclature of galago species. All participants expressed some degree of dissatisfaction with Hill’s species groups. Many described how it was proving increasingly problematic and inadequate as a means to organize newly collected laboratory, museum, and field data. By the end of the symposium, a consensus about species diversity had emerged which synthesized the current state of knowledge about galagos. The consensus of the participants was that the 11 species, identified by Olson (1979, 1986), most closely approximates the available data about galago species diversity. The 11 species are described.     

Asymmetrical habitat coupling of an aquatic predator—The importance of individual specialization

Predators should stabilize food webs because they can move between spatially separate habitats. However, predators adapted to forage on local resources may have a reduced ability to couple habitats. Here, we show clear asymmetry in the ability to couple habitats by Eurasian perch—a common polymorphic predator in European lakes. We sampled perch from two spatially separate habitats—pelagic and littoral zones—in Lake Erken, Sweden. Littoral perch showed stronger individual specialization, but they also used resources from the pelagic zone, indicating their ability to couple habitats. In contrast, pelagic perch showed weaker individual specialization but near complete reliance on pelagic resources, indicating their preference to one habitat. This asymmetry in the habitat coupling ability of perch challenges the expectation that, in general, predators should stabilize spatially separated food webs. Our results suggest that habitat coupling might be constrained by morphological adaptations, which in this case were not related to genetic differentiation but were more likely related to differences in individual specialization.     

The evolution of the mechanical properties of amniote bone

162 specimens from 19 species of amniote were tested for various mechanical and physical properties to ascertain whether there were characteristic differences between different groups. All mechanical properties showed very great variation. In general the reptiles were not inferior to the mammals and birds. The histology of living forms was compared to that of fossil forms, to see whether 'weak' histology was more characteristic of primitive amniotes. The earliest reptiles probably had rather complaint bone, but it was probably tough. Modern types of bone appeared over two hundred million years ago. Very specialised bone, like that of the bullae of whales and antlers, may have evolved only in the mammals, but the fossil record is not complete enough to assert this confidently.