he Achilles tendon is the largest, thickest, and strongest tendon in the human body. Problems with the Achilles tendon are frequent in athletes and the general population because of the increased incidence of sports-related injuries, which cause foot and ankle pain. [1][2][3][4] The area 5 cm proximal to the calcaneus is especially predisposed to tendinopathy and subsequent tearing due to vascular and biomechanical factors. Sonography plays an important role in the evaluation of tendon disorders, owing to its low cost, relative availability, noninvasiveness, and dynamic character. However, its diagnostic accuracy remains controversial. 5,6 Magnetic resonance imaging is a useful modality for imaging the Achilles tendon, but it is expensive and time-consuming.Shuai Fu, MD, Ligang Cui, MD, Xiaoxi He, MD, Yang Sun, MD Received January 20, 2016, Methods-A total of 326 healthy volunteers older than 18 years were divided into different groups by sex and age. The thickness, shear wave velocity (SWV) in sagittal and axial sections, and anisotropic coefficient of the Achilles tendon in a state of relaxation were obtained by conventional sonography and Virtual Touch imaging quantification elastography. These parameters were compared in different age and sex groups, and their correlations with age were evaluated.Results-The thickness of the Achilles tendon in men and women increased gradually with age, and it was larger in men than in women in each age group (P < .05). The SWV of the tendon in the sagittal section decreased slightly with age, but the sagittal and axial SWVs and anisotropic coefficient had no significant differences among different age groups (P > .05), and they also had no significant differences between men and women within any group (P > .05). The SWVs in the sagittal and axial sections and anisotropic coefficient had no correlation with age. Intraclass correlation coefficients for sagittal and axial SWVs obtained by 2 independent observers were 0.923 and 0.870, respectively.Conclusions-The thickness of the Achilles tendon increased gradually with age. We confirmed that tendinous elastographic anisotropy and the stiffness of the tendon had no significant correlation with age.

Passwords have been widely used in online authentication, and they form the front line that protects our data security and privacy. But the security of password may be easily harmed by insecure password generator. Massive reports state that users are always keen to generate new passwords by reusing or fine-tuning old secrets. Once an old password is leaked, the users may suffer from credential tweaking attacks. We propose a password reuse model PassTrans and simulate credential tweaking attacks. We evaluate the performance in leaked password datasets, and the results show that 67.51% of accounts is breakable under 1,000 guesses, indicating our model is accurate in capturing password reuse behavior.

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