Go to the location where you store your VM /home/ron/VirtualBox VMs/Semios Win7 /.Open .vbox in your favorite text editor to check if it is empty. Probably it is 🙂 In the same folder you should have file Semios Win7 .vbox-prev. Copy the contents of this file to Semios Win7.vbox, save, and try again.
In geometry, curvilinear coordinates are a coordinate system for Euclidean space in which the coordinate lines may be curved. These coordinates may be derived from a set of Cartesian coordinates by using a transformation that is locally invertible (a one-to-one map) at each point.
Gregorio Ricci-Curbastro (Italian: [ɡreˈɡɔːrjo ˈrittʃi kurˈbastro]; 12 January 1853 – 6 August 1925) was an Italian mathematician. He is most famous as the discoverer of tensor calculus.
With his former student Tullio Levi-Civita, he wrote his most famous single publication, a pioneering work on the calculus of tensors, signing it as Gregorio Ricci. This appears to be the only time that Ricci-Curbastro used the shortened form of his name in a publication, and continues to cause confusion.
Ricci-Curbastro also published important works in other fields, including a book on higher algebra and infinitesimal analysis,and papers on the theory of real numbers, an area in which he extended the research begun by Richard Dedekind.