Mach's Principle and the Origin of Inertia

The current status of Mach's principle is discussed within the context of general relativity. The inertial properties of a particle are determined by its mass and spin, since these characterize the irreducible unitary representations of the inhomogeneous Lorentz group. The origin of the inertia of mass and intrinsic spin are discussed and the inertia of intrinsic spin is studied via the coupling of intrinsic spin with rotation. The implications of spin-rotation coupling and the possibility of history dependence and nonlocality in relativistic physics are briefly mentioned.Comment: 14 pages. Dedicated to Carl Brans in honor of his 80th birthday. To appear in the Brans Festschrift; v2: typo corrected, published in: At the Frontier of Spacetime, edited by T. Asselmeyer-Maluga (Springer, 2016), Chapter 10, pp. 177-18

Genetic and Environmental Influences on Semantic Verbal Fluency Across Midlife and Later Life

Despite the relevance of semantic fluency measures to risk for dementia and psychiatric disorders, little is known about their genetic and environmental architecture in mid-to-late life. Participants represent 21,684 middle-aged and older adult twins (M = 60.84 years, SD = 11.21; Range 40-89) from six studies from three countries participating in the Interplay of Genes and Environment across Multiple Studies (IGEMS) consortium. All completed the same measure of semantic fluency (naming animals in 60 seconds). Results revealed small-to-moderate phenotypic associations with age and education, with education more strongly and positively associated with fluency performance in females than males. Heritability and environmental influences did not vary by age. Environmental variance was smaller with higher levels of education, but this effect was observed only in males. This is the largest study to examine the genetic and environmental architecture of semantic fluency, and the first to demonstrate that environmental influences vary based on levels of education

Connatal (fetal) hydrocephalus - an acquired pathology?

We investigated the etiology of hydrocephalus present at birth, i.e. of fetal hydrocephalus. Both inherited and dysraphic major malformations are very rare. Intraventricular hemorrhages and viral infections during pregnancy are among the proposed etiologies; they are supported more by anatomical, physiopathological and experimental findings than by clinical evidence. Cases of fetal intraventricular hemorrhages cited in the literature are anecdotical, and the reports fail to identify maternal or fetal predisposing factors. The role of viruses in the etiology of connatal hydrocephalus has been postulated on the basis of epidemiological considerations in human pathology and of a considerable amount of experimental studies in animals. Investigations were generally focused on aqueduct ependyma, but research should also address other structures involved in the genesis of hydrocephalus (choroid plexus, extraventricular CSF pathways, including arachnoid villi). Furthermore, experimental evidence has emerged concerning a number of toxins and of drugs administered during pregnancy, which are thought to be involved in the genesis of hydrocephalus: once more, the conclusions reached in these experimental trials lend further credence to the human epidemiological data linking pregnancy disturbances with fetal hydrocephalus. Since most of these toxic agents are also thought to induce major malformations, we could assume the degree of their effect to depend on the embryonal stage affected: the earlier the action, the worse the malformatio