Tune Shift in Beam-Beam Collisions with an Arbitrary Crossing Angle

A stroller has a pair of parallel front legs, an inverted U-shaped handle rod foldably connected to the upper ends of the front legs, a pair of parallel rear legs interconnected by a handrest and pivoted to specified portions of the front legs crosswise respectively, a pair of stays bent at an obtuse angle and pivoted at their upper ends to the handle rod, a transverse rod interconnecting the lower ends of the stays, a pair of links each having one end pivotally supported by the transverse rod and the other end pivoted to each of the rear legs at a specified position near the lower end of the rear leg, a U-shaped footrest pivotally supported at its opposite ends by the transverse rod and pivoted at specified portions to the front legs near the lower ends thereof, and locking members interconnected by a connecting rod and pivoted to specified midportions of the rear legs respectively. Each of the locking members is provided with a spring for pressing the locking member against the transverse rod engaged in a cutout of the locking member when the stroller is in condition for use. The front legs and rear legs are fixedly provided at their lower ends with transverse wheel shafts carrying front wheels and rear wheels respectively.