1. Introduction
2. Sample and Observations
2.1. The COSMOS Superstructure at  $z\approx0.84$
2.2. Target Selection
2.3. Observations
2.4. Data Reduction
2.5. Flux Calibration
2.6. Redshift Measurements
2.7. Final Sample
3. Determination of Galaxy Properties
4. Results
5. Discussion
5.1. Halting of Star Formation in the Outskirts of Clusters
6. Conclusions