Plant delta(15)N associated with arbuscular mycorrhization, drought and nitrogen deficiency

It has long been evident that plant (15)N chiefly reflects the processes which fractionate (15)N/(14)N rather than the (15)N of plant N source(s). It has emerged recently that one of the most important fractionating processes contributing to the whole plant (15)N is the presence/absence, type or species of mycorrhiza, especially when interacting with nutrient deficiency. Ecto- and ericoid mycorrhizas are frequently associated with (15)N-depleted foliar (15)N, commonly as low as -12 per thousand. As shown by the present study, plants having no mycorrhiza, or those infected with various species of arbuscular mycorrhiza (AM)-forming fungi, interact with varying concentrations of soil nitrogen [N] and moisture to enrich plant (15)N by as much as 3.5 per thousand. Hence the lack of a mycorrhiza, or variation in the species of AM-forming fungal associations, can account for about 25% of the usually reported variations of foliar (15)N found in field situations and do so by (15)N enrichment rather than depletion. Copyright 1999 John Wiley & Sons, Ltd.     

Comment on an equation of motion with radiation reaction

An equation of motion with radiation reaction proposed by Ringermacher is shown to have an added constraint if momentum conservation is to be maintained. As a consequence the equation can either be interpreted as having a variable rest mass or it can be recast in a form first derived by Eliezer. In either case it leads to unphysical results.     

A minimum photon “rest mass” — Using Planck's constant and discontinuous electromagnetic waves

Reasons for taking1/2h/c ² in cgs units as an equivalent in grams for the photon “rest mass” are given. Its numerical value of3.68×10 ^?48 g corresponds to the minimum mass equivalent energy for one half-cycle of an electromagnetic dipole field distribution, which is discontinuous. For the fluid models that are discussed, this field distribution corresponds somewhat to a hydrodynamic toroidal vortex which is stationary—if we use toroidal coordinates and assume that the ring origin has the radial velocity c, that the gauge is defined by the ring origin diameter, and that free space is represented by a two-fluid model (the fluids oppositely charged). There are mappings which can transform such toroidal entities (photons) into spherical ones. The toroidal entities are possible candidates for the role of “hidden variables.”     

Nonstoichiometry and defects in V2O3

The structural mechanism which accommodates nonstoichiometry in V₂O₃ was investigated by transmission electron microscopy. The existence of distinct diffuse scattering was observed as the boundary of the homogeneity range was approached. The analysis of the diffuse scattering indicates the formation of one-dimensional microdomains in the c direction having a structure similar to VO₂. Orientation relations between V₂O₃ and V₃O₅ (which is formed from V₂O₃ by heat treatment in an oxidizing atmosphere) show that V₃O₅ is formed by redistribution of vanadium ions among the octahedral interstitial sites of common close-packed sublattice consisting of oxygen ions. Possible relations between the present observations and physical properties in nonstoichiometric V₂O_3+x are discussed.