Question: where is the descending aorta located in the mediastinum
[{'answer': 'posterior mediastinal cavity', 'provenance': [{'wikipedia_id': '3091684', 'title': 'Descending thoracic aorta', 'start_paragraph_id': 1, 'start_character': 142, 'end_paragraph_id': 1, 'end_character': 170, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '3091684', 'title': 'Descending thoracic aorta', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 452, 'bleu_score': 0.974188104609039, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3866448633035644911}, 'section': 'Section::::Abstract.'}]}]