The phrase "a middle stage" is correct and usable in written English.
It can be used to describe an intermediate phase in a process or development.
Example: "The project is currently in a middle stage, where we are evaluating the results of our initial tests before moving forward."
Alternatives: "an intermediate phase" or "a transitional stage".
Here we assess the laminar fate potential of progenitors at a middle stage of cortical development.
During a middle stage, meadow-steppe elements prevailed; bunodont rodents (hamsters, ground squirrels, birch mice, mice) dominated voles.
Thereby the phase-separation behaviour of oligomers changed from liquid liquid phase separation to crystallization at a middle stage in the polymerization and then needle-like crystals were formed on the surface of the microspheres.
THE New York Landmarks Conservancy's restoration of Astor Row, the little brick houses at 8 to 62 West 130th Street, is now at a middle stage, with some houses still almost derelict, some in mid-restoration and some completed.
Much as we might consider Edward Weston's celebrated images of nudes, seashells and peppers an enduring pinnacle of the modernist aesthetic in photography, they represent only a middle stage in the photographer's career.
Diplomats, United Nations officials and delegates themselves said the talks were at a middle stage, with serious discussions finally beginning over the shape, content and personnel for the provisional executive authority and provisional council that all the factions agreed to set up when they arrived here on Monday.
Another closely watched drug being developed by Pfizer, Johnson & Johnson and Elan has had mixed results in a middle-stage clinical trial.
The drug had mixed results in a middle-stage study, but the results were encouraging enough that the companies have moved into the final-stage of testing.
This research was conducted as a middle-stage solution for tamper protection technology of next generation content such as multi-view images.
In a middle-stage trial of 195 patients with staph skin infections, it cured 96% of the patients; vancomycin had a 90% cure rate.
However, these three texts represent a stable, middle stage in Alexander's research and collectively provide a sufficiently self-contained set of ideas to be described (for the ease of the following discussion) as his 'second theory'.
