RESUMEN
Objective To study the characteristics of upper airway airflow dynamics during inspiration after unilateral total maxillectomy by means of computer numerical simulation. Methods Based on postoperative CT images of three patients with unilateral maxillary tumor, three-dimensional upper airway structures of the patients were reconstructed, and the upper airway airflow was simulated numerically by computational fluid dynamics method. Results The upper airway airflow trends of the patients during inspiration after unilateral maxillectomy were obtained. Airflow in the defect nasal cavity was separated, and made the spacious vortices of low velocity occurred throughout the entire maxillary defect cavity. Conclusions The upper airway trends of the three patients were generally in conformity with each other after their unilateral total maxillectomy, which illustrated that the respiratory patterns of such patients were of universality. Unilateral total maxillectomy resulted in structure changes of patients’ upper airway, which could disturb the upper airway airflow patterns，and affect the physiological functions of patients’ upper airway. Numerical simulation of patients' upper airway airflow after unilateral total maxillectomy could help to explain the phenomena of nasal drying and crusting, secretion accumulation as well as other symptoms of the kind of patients.
RESUMEN
Este artículo revisa tres de las principales causas de amenaza a la diversidad biológica, como son la fragmentación y pérdida del hábitat, así como la invasión de especies exóticas, principalmente en lo que compete a sus implicaciones evolutivas. Los efectos de la fragmentación y/o pérdida del hábitat pueden revisarse a la luz de la sinergia entre factores demográficos y genéticos que moldean cambios evolutivos o que llevan a las poblaciones al vórtice de la extinción. Las invasiones biológicas, aunque han generado pérdidas considerables en la diversidad biológica, ofrecen un escenario interesante para estudiar procesos evolutivos contemporáneos.
This paper reviews three of the main threats to biological diversity, such as habitat fragmentation /habitat loss, and invasion of exotic species, mainly from their evolutionary implications. Effects of habitat fragmentation/habitat loss could be addressed by looking at the synergy between demographic and genetic factors that together shape evolutionary changes or otherwise bring populations to extinction vortex. Biological invasions, in spite of their strong negative effects on biological diversity, offer an interesting scenario to study contemporary evolutionary processes.