Understanding the functioning of natural systems is not easy, although there is general agreement that understanding complex systems is an important goal for science education. Defining what makes a natural system complex will assist in identifying gaps in research on student reasoning about systems. The goal of this commentary is to propose a framework that explicitly defines the ways in which...

A compact reconfigurable antenna with an omnidirectional mode and four directional modes is proposed. The antenna has a main radiator and four parasitic elements printed on a dielectric substrate. By changing the status of diodes soldered on the parasitic elements, the proposed antenna can generate four directional radiation patterns and one omnidirectional radiation pattern. The main beam dire...

in western countries we assist at the paradox that fertility is socially discouraged by a mindset that depicts fertility as a resource to exploit as late as possible. so, couples have high expectative about the advantages of delayed parenthood, but they are scarcely informed about its risks. scientific data suggests to anticipate the first pregnancy, but social pressures impose to wait, though ...

We give necessary conditions for the existence of perturbative heterotic and common sector type II string warped compactifications preserving four and eight supersymmetries to four spacetime dimensions, respectively. In particular, we find that the only compactifications of heterotic string with the spin connection embedded in the gauge connection and type II strings are those on Calabi-Yau man...

We investigate the nonlinear realization of spontaneously broken N = 2 superconformal symmetry in 4 dimensions. We particularly study NambuGoldstone degrees of freedom for the partial breaking of N = 2 superconformal symmetry down to N = 1 super-Poincaré symmetry, where we get the chiral NG multiplet of dilaton and the vector NG multiplet of NG fermion of broken Q-supersymmetry. Evaluating the ...

We construct infinite families of topologically isotopic, but smoothly distinct knotted spheres, in many simply connected 4-manifolds that become smoothly isotopic after stabilizing by connected summing with S2×S2, and as a consequence, analogous families of diffeomorphisms and metrics of positive scalar curvature for such 4-manifolds. We also construct families of smoothly distinct links, all ...