11. In some cases, the second-order approximation is also called " paraxial ". 12. This yields the paraxial Helmholtz equation. 13. Fgf from the paraxial mesoderm has been suggested as a source of neural crest inductive signal. 14. It is often combined with the paraxial approximation in techniques such as ray transfer matrix analysis. 15. Knockout studies in mice indicate that this gene is important for specification of paraxial mesoderm structures. 16. Since this solution relies on the paraxial approximation, it is not accurate for very strongly diverging beams. 17. The paraxial approximation is used in Gaussian optics and " first-order " ray tracing. 18. The segmentation pattern observed in the peripheral nervous system ( PNS ) derives itself from the paraxial mesoderm. 19. The paraxial mesoderm is arranged along the sides of the notochord and neural tube as repetitive structures called somites. 20. Gaussian beam propagation is a simple paraxial physical optics model for the propagation of coherent radiation such as laser beams.
