A generalization of the S-function method applied to a Duffing-Van der Pol forced oscillator

In [1,2] we have developed a method (we call it the S-function method) that is successful in treating certain classes of rational second order ordinary differential equations (rational 2ODEs) that are particularly `resistant' to canonical Lie methods and to Darbouxian approaches. In this present paper, we generalize the S-function method making it capable of dealing with a class of elementary 2ODEs presenting elementary functions. Then, we apply this method to a Duffing-Van der Pol forced oscillator, obtaining an entire class of first integrals

Unconventional strong pinning in the low temperature phase of U_.9725Th_.0275Be_13

We investigated low field vortex dynamics in a single crystal of U_.9725Th_.0275Be_13. We found a sharp transition in the vortex creep rate at the lower transition temperature T_c2, coincident with the second jump in the specific heat. In the high-temperature phase, rather strong creep rates are observed. In the low temperature phase, the rates drop to undetectabely low levels. This behaviour indicates that a very strong pinning mechanism is present in the low temperature phase of U_.9725Th_.0275Be_13, which could be explained by the existence of domain walls, separating discreetly degenerate states of a superconductor, that can sustain fractional vortices and thus act as very strong pinning centers.Comment: 2 pages, 2 figures, accepted in PhysicaB, LT2

Comparison of the physical properties of vermicompost from paper mill sludge and green compost as substitutes for peat-based potting media

The properties of vermicompost, green compost, and their mixes as substitutes for peat were evaluated regarding their recommendation for potting media. The mixes with a maximum of 50% of vermicompost or green compost had acceptable air filled porosity (AFP) and easily available water (EAW). In the vermicompost the level of organic matter (OM), dry bulk density (DBD) and shrinkage were acceptable; however, the AFP and EAW together were not at the recommended level in the different batches; as a consequence, vermicompost should not be used alone for potting media. In the green compost, the level of OM was low which increased the DBD and consequently the AFP was diminished. The particle size distribution (PSD) was different among peat, vermicompost and green compost. The coarse peat had the lower proportion of particles from 0.25 to 2.00 mm (41%) whereas the green compost had the lower coarseness index (CI: percentage by weight of particles larger than 0.5 mm in diameter), 48.4%. The direct effect of the PSD, OM and DBD in the water and air availability was confirmed. Moreover, there were high correlations between the OM, DBD, shrinkage, pore volume and PSD with the water release curve. Those properties should be considered in order to increase the level of substitution of vermicompost in peat-based potting media