code: @Override
    public List<IScan> getScansByRtUpper(double rt) {
      Map.Entry<Double, List<IScan>> ceilingEntry = getMapRt2scan().ceilingEntry(rt);
      if (ceilingEntry == null) {
        return null;
      }
      List<IScan> scans = ceilingEntry.getValue();
      if (scans != null) {
        return scans;
      }
      return null;
    }
docs: Scan List with the closest RT greater or equal to the provided one are returned.