The ornamental design for a centrifuge, as shown and described.
FIG. 1 is an isometric view of our new centrifuge design;
FIG. 2 is an isometric view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a cross sectional view thereof, taken along line 5-5 of FIG. 3;
FIG. 6 is a rear view thereof;
FIG. 7 is a left side view thereof; and,
FIG. 8 is a top view thereof.
The features of the centrifuge shown in broken dash lines which define the bounds of the claimed design are for illustrative purposes only and form no part of the claimed design. The features of the centrifuge shown in broken dot-dash lines are for the purpose of illustrating environment of the claimed design and form no part of the claimed design.