public static String getMatrixChunk(String sessionID, int elements) throws MalformedURLException, ServiceException, RemoteException {
	Call call = getStandardCall("getMatrixChunk");
	call.addParameter("op1", XMLType.XSD_STRING, ParameterMode.IN );
	call.addParameter("op2", XMLType.XSD_INT, ParameterMode.IN );
	call.setReturnType(XMLType.XSD_BASE64 );
	call.setEncodingStyle(Constants.URI_SOAP12_ENC);
	
	return (String) call.invoke( new Object [] { sessionID, new Integer(elements) });
}