The difference between them is the Pure Sine Wave inverter produces a better and cleaner current. They are also considerably more expensive. You might find it practical to get a small Pure Sine Wave inverter for any special need you may have, and also a larger Modified Sine Wave inverter for the rest of your applications.
Elm Trees can live over 100 years in their natural environment.
Examine the tree in the winter. Elms are deciduous, meaning they shed their leaves once each year, starting in the fall. By the winter, they will be bare of leaves, and then in the spring they will start to re-grow their leaves. If you notice this foliage pattern, you might have an elm.