Symmetry and asymmetry in electrodynamics from Rowland to Einstein

Halfway through the paper in which he laid down the foundations for the theory of special relativity, Einstein concludes that “the asymmetry mentioned in the Introduction … disappears.” Making asymmetry disappear has proved to be one of Einstein's many significant moves in his annus mirabilis of 1905. This elimination of asymmetry has led many commentators to claim that Einstein was motivated by either an aesthetic or an epistemic argument which gives priority to symmetry over asymmetry. Following closely the development of electrodynamics in the period from 1880 to 1905 and the usage of the related terms reciprocity and symmetry, we suggest a different way of understanding Einstein's motivation and the path he took. In contrast to the received view, we argue that Einstein responded to a debate in the literature on electrodynamics and that he was concerned neither with an aesthetic nor with an epistemic argument; rather, his reasoning was physical in the best sense, and most original. We will show that by providing a new perspective on the relation between electricity and magnetism, Einstein succeeded in bringing the discussion of symmetry in electrodynamics to an end.     

The penetrance of dominant erythropoietic protoporphyria is modulated by expression of wildtype FECH.

Erythropoietic protoporphyria (EPP) is an inherited disorder of heme biosynthesis caused by a partial deficiency of ferrochelatase (FECH, EC 4.99.1.1). EPP is transmitted as an autosomal dominant disorder with an incomplete penetrance. Using haplotype segregation analysis, we have identified an intronic single nucleotide polymorphism (SNP), IVS3-48T/C, that modulates the use of a constitutive aberrant acceptor splice site. The aberrantly spliced mRNA is degraded by a nonsense-mediated decay mechanism (NMD), producing a decreased steady-state level of mRNA and the additional FECH enzyme deficiency necessary for EPP phenotypic expression.     

New records of western Trichoptera with notes on their biology

Western records for 27 species of Trichoptera are given; a majority of the records are from the Beartooth Mountains of northwestern Wyoming. In addition, examples of variation in the male genitilia of Limnephilus coloradensis (Banks) are figured and the female is described. Some comments regarding the larvae of Allomyia ( Imania ) are presented.     

No signature of clear CO2 ice from the 'cryptic' regions in Mars' south seasonal polar cap

The seasonal polar ice caps of Mars are composed mainly of CO2 ice. A region of low (< 30%) albedo has been observed within the south seasonal cap during early to mid-spring. The low temperature of this 'cryptic region' has been attributed to a clear slab of nearly pure CO2 ice, with the low albedo resulting from absorption by the underlying surface. Here we report near-infrared imaging spectroscopy of the south seasonal cap. The deep and broad CO2 absorption bands that are expected in the near-infrared with a thick transparent slab of CO2 ice are not observed. Models of the observed spectra indicate that the low albedo results from extensive dust contamination close to the surface of a CO2 ice layer, which could be linked to atmospheric circulation patterns. The strength of the CO2 absorption increases after mid-spring, so part of the dust is either carried away or buried more deeply in the ice layer during the CO2 ice sublimation process.     

Effect of concanavalin A on the development of blastulae in Pleurodeles waltlii (Amphibia, Urodeles)]

The effect of concanavalin A (con A) on Pleurodeles waltlii blastulae was studied by incubating the eggs in presence of lectin. It was found that the protein exercised an inhibitory effect upon morphogenesis. This inhibition was concentration dependent. In certain cases, the inhibitory effect of con A was attenuated by alpha-D-methyl-mannose (0,05 M).