code: @Override
  	public boolean isNmr() {
  
  		// old implementation was:
  		//return nmrflag;
  
  		if (pdbHeader.getExperimentalTechniques()!=null) {
  			return ExperimentalTechnique.isNmr(pdbHeader.getExperimentalTechniques());
  		} else {
  			// no experimental technique known, we try to guess...
  			if (nrModels()>1) {
  				if (pdbHeader.getCrystallographicInfo().getSpaceGroup()!=null) {
  					// multimodel, sg defined, but missing cell: must be NMR
  					if (pdbHeader.getCrystallographicInfo().getCrystalCell()==null)
  						return true;
  					// multi-model, sg defined and cell unreasonable: must be NMR
  					if (!pdbHeader.getCrystallographicInfo().getCrystalCell().isCellReasonable())
  						return true;
  				} else {
  					// multi-model and missing space group: must be NMR
  					return true;
  				}
  			}
  		}
  		return false;
  	}
docs: Whether this Structure is a NMR structure or not.
  It will first check the experimental technique and if not present it will try
  to guess from the presence of more than 1 model and from b-factors being 0 in first chain of first model
  @return true if NMR, false otherwise