By forming the intersections of the parity and time reversal equivalence classes of physical entities that are represented by differential forms and differential form densities, a number of subsets of discrete symmetry classes for electromagnetic systems can be generated. Only one of these subsets is consistent with elementary thermodynamic arguments for dissipative systems and at the same time yields the notion that both charge and mass are spacetime scalars. This subset is not in correspondence with the two self-consistent presentations that (...) now are implied in the literature. (shrink)

Points of agreement and disagreement with Post's remarks on the author's discussion of the criteria to be used for reducing the eight parity and time reversal symmetry choices that the formally possible for electromagnetic quantities are noted.

Large‐scale characterization of the human microbiota has largely focused on Western adults, yet these populations may be uncharacteristic because of their diets and lifestyles. In particular, the rise of “Western diseases” may in part stem from reduced exposure to, or even loss of, microbes with which humans have coevolved. Here, we review beneficial microbes associated with pathogen resistance, highlighting the emerging role of complex microbial communities in protecting against disease. We discuss ways in which modern lifestyles and practices may deplete (...) physiologically important microbiota, and explore prospects for reintroducing or encouraging the growth of beneficial microbes to promote the restoration of healthy microbial ecosystems. (shrink)

Culture can be defined as “group typical behaviour patterns shared by members of a community that rely on socially learned and transmitted information”. Once thought to be a distinguishing characteristic of humans relative to other animals it is now generally accepted to exist more widely, with especially abundant evidence in non-human primates, cetaceans, and birds. More recently, cumulative cultural evolution has taken on this distinguishing role. CCE, it is argued, allows humans, uniquely, to ratchet up the complexity or efficiency of (...) cultural traits over time. This “ratchet effect” gives the capacity to accumulate beneficial modifications over time beyond the capacities of a single individual. Mesoudi and Thornton define a core set of criteria for identifying CCE in humans and non-human animals that places emphasis on some performance measure of traits increasing over time. They suggest this emphasis is also pertinent to cultural products in the aesthetic domain, but is this the case? Music, art and dance evolve over time, but can we say they gain beneficial modifications that increase their aesthetic value? Here we bring together perspectives from philosophy, musicology and biology to build a conceptual analysis of this question. We summarise current thinking on cumulative culture and aesthetics across fields to determine how aesthetic culture fits into the concept of CCE. We argue that this concept is problematic to reconcile with dominant views of aesthetics in philosophical analysis and struggles to characterise aesthetic cultures that evolve over time. We suggest that a tension arises from fundamental differences between cultural evolution in aesthetic and technological domains. Furthermore, this tension contributes to current debates between reconstructive and preservative theories of cultural evolution. (shrink)

We show that it is possible to generalize the Ursell–Mayer cluster formalism so that it may cover also the statistics of Internet websites. Our starting point is the introduction of an extra variable that is assumed to take account, as will be explained, of the nature of the Internet statistics. We then show, following the arguments in Mayer, that one may obtain a phase transition-like phenomena.

Previous statements concerning the reduction of possible parity and time reversal choices for electromagnetic quantities are amplified for the sake of clearer understanding.