private BitSet genericSelect(String str) {
		boolean found = false;
		int nop = model.getNumberOfParticles();
		BitSet bs = new BitSet(nop);
		Matcher matcher = ALL.matcher(str);
		if (matcher.find()) {
			for (int k = 0; k < nop; k++)
				bs.set(k);
			found = true;
		}
		if (!found) {
			matcher = NONE.matcher(str);
			if (matcher.find()) {
				found = true;
			}
		}
		if (found)
			model.setParticleSelectionSet(bs);
		return found ? bs : null;
	}