Size-dependent nonlinear optical properties of modification-free transition metal dichalcogenide (TMD) nanosheets are reported, including MoS2 , WS2 , and NbSe2 . Firstly, a gradient centrifugation method is demonstrated to separate the TMD nanosheets into different sizes. The successful size separation allows the study of size-dependent nonlinear optical properties of nanoscale TMD materials for the first time. Z-scan measurements indicate that the dispersion of MoS2 and WS2 nanosheets that are 50-60 nm thick leads to reverse saturable absorption (RSA), which is in contrast to the saturable absorption (SA) seen in the thicker samples. Moreover, the NbSe2 nanosheets show no size-dependent effects because of their metallic nature. The mechanism behind the size-dependent nonlinear optical properties of the semiconductive TMD nanosheets is revealed by transient transmission spectra measurements.

A random sample of 119 young, healthy Han Chinese adults (56 men and 63 women) between the age of 18 and 25 years (mean, 22.7 y) in PR China was obtained for this study. By the guidance of standard methods, based on Farkas's anthropometric measurements in craniofacial region, 12 nasal soft tissue landmarks and 12 linear and 3 angular measurements were chosen. The linear measurements were taken directly, whereas the angular measurements were taken by photogrammetric method. Eight nasal proportion indices were calculated according to the linear measurements. The application of the independent-samples t-test showed sex dimorphism in most parameters of the nasal region. All the linear measurements were larger in men than in women, whereas all the angular measurements were smaller in men than in women. The significant differences in partial parameters between men and women have been proved. Ten of 12 linear measurements, 1 of 3 angular measurements, and 3 of 8 nasal proportion indices showed significant sexual dimorphism (P < 0.01). Compared with other racial/ethnic groups, the nasal anthropometric measurements and proportion indices of Han Chinese adults were different, to some extent. This study could provide credible and objective reference material for plastic and maxillofacial surgeons for the external nasal soft tissue evaluation and planning of the cosmetic nasal surgery. Besides, these results could be a useful guidance for preoperative and postoperative evaluations of secondary rhinoplasty in nasal deformity associated with cleft lip and palate.

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The normal measurement values of anatomic structures of orbital soft tissue and the proportional indices for normal young Han Chinese adults provided reference data for periorbital cosmetic and reconstructive surgery.

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