Characterization of Powder Cosmetics Based on Friction Dynamics.

Frictional properties are one of the most important physical factors in the design of powder cosmetics. In this study, 21 powder cosmetics were applied to artificial skin, and their friction characteristics were evaluated using a sinusoidal motion friction evaluation system. Three friction profiles were observed that depended on the sliding velocity. Principal component analysis showed that the principal component (Z), which characterized the friction dynamics of powder cosmetics, included the static friction coefficient (µ s), the kinetic friction coefficient (µ k), the delay time (δ), and the viscosity coefficient (C). Furthermore, a cluster analysis on Z suggested that powder cosmetics can be classified into three groups according to their friction dynamics. These results may be helpful to understand the phenomena that occur during the application of powder cosmetics.

Usefulness and accuracy of a handheld ultrasound device for epidurssal landmark and depth assessment by anesthesiology residents.

PURPOSE: The aim of this study was to assess the usefulness and accuracy of a handheld ultrasound device (Accuro, Rivanna Medical, Charlottesville, VA, USA) for epidural landmark and depth assessment when epidural anesthesia is performed by residents. METHODS: Patients scheduled to receive epidural anesthesia were randomly assigned to the Accuro group (group A) or control group (group C). In group A, the depth to the epidural space and the appropriate place for epidural insertion according to Accuro was recorded. In group C, epidural anesthesia was performed using a conventional method. The following were recorded and compared between the groups: time from puncture of the Tuohy needle to loss of resistance, number of Tuohy needle redirects, and epidural-related complications. In group A, depth to the epidural space estimated by Accuro (Accuro Depth) and the actual depth measured with a marker on the needle (Needle Depth) were recorded and compared. RESULTS: Sixty patients were enrolled during the study period. There was no significant difference between the groups regarding the median or range of time required to locate the epidural space. The number of Tuohy needle redirects was 0 (0-3) in group A and 1.5 (0-7) in group C (P = 0.012). Accuro Depth was less than Needle Depth [mean difference, 0.85 cm (95% CI-1.10 to - 0.62), SD = 0.62]. CONCLUSIONS: Although there was no significant difference in time from Tuohy needle puncture to loss of resistance, Accuro reduced the number of Tuohy needle redirects and accurately indicated the depth to the epidural space. Accuro may be useful for identifying the needle insertion point and estimating depth to the epidural space when residents perform epidural anesthesia.

Characterization of Cosmetic Dispersions Based on Friction Dynamics.

Frictional properties are one of the most important physical factors in the design of cosmetic dispersions in which solid particles are dispersed in a liquid. The effects of ingredients and formulations on frictional properties have been previously reported. In this study, the frictional properties of 33 cosmetic dispersions were evaluated using a sinusoidal motion friction evaluation system when applied on an artificial skin. A detailed analysis of the velocity dependence of the friction coefficient demonstrated that all cosmetic dispersions exhibited stable pattern and the friction behavior did not change during the round trip. We analyzed friction-based parameters by principal component analysis and demonstrated that the principal components Z 1 and Z 2 include the static friction coefficient µ s, kinetic friction coefficient µ k, delay time δ, and viscosity coefficient C, and that these factors are involved in characterizing friction dynamics. The cluster analysis on Z 1 and Z 2 suggested that these dispersions can be classified in three groups with respect to friction dynamics. These results can help understand the characteristics of cosmetics and control their function and utility.