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Brick-red deposits with palygorskite (Pal) as the main ingredient are widely distributed in nature, but these have not been deployed at a large scale in industry because of their inherent deep colors. In the present study, the brick-red Pal deposit was treated hydrothermally in various reaction media including water, a urea solution, and a thiourea solution. The effects of these processes on the structure, physicochemical features, and color of Pal were studied intensively to understand the structure and composition of the brick-red Pal deposit and to lay a theoretical foundation for the extension of its industrial application. The changes in structural features after hydrothermal treatment were studied by Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, magic-angle spinning nuclear magnetic resonance, and Mossbauer spectroscopy techniques. The results indicated that the color of brick-red Pal did not change after hydrothermal treatment in water or in a urea solution, and the color changed to gray-white after treatment in the thiourea solution. The rod-like crystal morphology of Pal was retained throughout the experiments and no significant change in the main associated minerals, including feldspar, muscovite, and quartz, was observed after hydrothermal treatment. The dissolution of associated hematite (α-Fe2O3 and the reduction of Fe(III) species are the main reason for the change of Pal from brick-red to gray-white.

Femoroacetabular impingement (FAI) has been accepted as a potential cause of idiopathic hip pain and osteoarthritis. Few cases of FAI have been reported in the Chinese population. We reviewed radiographic features of patients with idiopathic hip pain to characterize FAI in the Chinese population, any alternative radiographic measures, and potential symptom association. All anteroposterior pelvic radiographs of outpatients (n = 1,128) between December 2007 and August 2008 were reviewed. The radiographic measurements, including anteroposterior alpha angle (AP-α), radial height/radius ratio (R1), and 1/2 radial height/radius ratio (R2) as well as crossover signs, were recorded on both hip joints of all patients. The differences in AP-α, R1, and R2 were compared between cam-type hips (including mixed FAI) and non-cam-type hips (including non-FAI). From the group of patients, 269 were eligible for further evaluation, including those exhibiting FAI at the site of complaint (n = 38) or without symptoms (n = 7). FAI was significantly associated with hip pain (p = 0.009). For painful hips, the frequency of FAI was higher in males than in females (p = 0.038). AP-a was significantly higher in cam-type hips than in non-cam-type hips for either gender (p < 0.001, p < 0.001). R1 was comparable between the 2 subgroups for either gender (p > 0.05, p > 0.05), whereas R2 differed significantly (p < 0.001, p < 0.001). The occurrence of FAI was underestimated in Chinese patients showing negative radiographic findings with idiopathic hip pain. In addition, R2 was used to differentiate cam-type FAI from non-cam-type FAI.