A model for the collision between a sand grain and a body of yardang material is established by using the principles of classical mechanics. A new nondimensional parameter, the "abrasion number" A(n), is derived from the model. The volume removed per impact for different targets is proportional to A(n) approximately. As an indicator of the energy ratio of the impacting material to the target material, A(n) not only reflects the previous "abrasion law" but also introduces two dominant mechanical parameters, Young's modulus and yield stress. We propose A(n) to be a similarity criterion for abrasion experiments. The practicability of the model under natural conditions is examined by an example. It is concluded that the abrasion rates of yardangs in the western Qaidam basin, China, are 0.011-0.398 mm/yr in the period of 1986 to 2010 and remarkable abrasion events generally correspond with strong wind conditions. The model will be helpful for reconstructing the history of aeolian activities from the morphologies of yardangs in the arid regions on Mars.

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The purpose of the study is to evaluate the effectiveness and safety of transarterial chemoembolization (TACE) with pingyangmycin-lipiodol emulsion for the treatment of symptomatic giant hepatic haemangioma. Four hospitals (The Second Hospital of Shandong University, Qilu Hospital of Shandong University, Shandong Provincial Hospital and Jinan Municipal Hospital) participated in this study during 2002-2012. A total of 836 patients with symptomatic giant haemangioma were treated with pingyangmycin-lipiodol emulsion via selective TACE. The patients were followed-up for 12 months-10 years. The effectiveness of the treatment was evaluated by symptom assessments and upper abdominal magnetic resonance imaging or computed tomography. TACE was successfully performed for a total of 1120 lesions in 836 patients. Success rate of the procedure was 100 %. The mean diameter of the haemangiomas was significantly reduced after the interventional therapy (mean diameter 9.6 ± 0.8 vs. 3.6 ± 0.5 cm; P < 0.05). Symptom relief was achieved in all the patients during the follow-up period. No mortality was identified. TACE with pingyangmycin-lipiodol emulsion is a safe, feasible, and effective treatment for the giant symptomatic hepatic haemangioma.