JOURNAL OF COSMETIC SCIENCE 108 general, African-American hair is looser in curl and curl degree increases in the order of Jamaican Ghanaian Liberian Kenyan. The cross-sectional area and Young’s modu- lus values are infl uenced by ethnicity, while break stress is infl uenced by both ethnicity and the degree of curl in hair. DSC and 2-D gel experiments suggest that structural and chemical composition of curly hair from different ethnic groups may also vary. Collec- tively, these results show that both curl type and ethnicity are important factors to con- sider when evaluating the behavior of hair, which may potentially impact the hair’s response to treatments and processes. ACKNOWLEDGMENTS The authors express their genuine thanks to Hui (Stacey) Tang for her knowledge and help with statistical methods and analyses and Charles Flemming for his contributions involving amino acid analysis. We would also like to acknowledge all of our colleagues from all over the world for special operations in obtaining hair, comments, discussions and support of our work. REFERENCES (1) K. Keis, K. R. Ramaprasad, and Y. K. Kamath, Studies of light scattering from ethnic hair fi bers, J. Cosmet. Sci., 55, 49–63 (2004). (2) C. R. Robbins, C. Reich, and J. Clarke, Hair manageability, J. Soc. Cosmet. Chem., 37, 489–499 (1986). (3) M. L. Garcia and J. Diaz, Combability measurements of human hair, J. Soc. Cosmet. Chem., 27, 379–398 (1976). (4) T. A. Evans, T. N. Ventura, and A. B. Wayne, The kinetics of hair reduction: Repairing effects of diglu- cosyl gallic acid on coloring-damaged hair, J. Soc. Cosmet. Chem., 45, 279–298 (1994). (5) R. de la Mettrie, D. Saint-Léger, G. Loussouarn, et al., Shape variability and classifi cation of human hair. A worldwide approach, Hum. Biol. 79, 265–281 (2007). (6) G. Loussourarn, A. L. Garcel, I. Lozano, et al., World diversity of hair curliness: A new method of assess- ment, J. Dermatol., 46, 2–6 (2007). (7) A. Syed, A. Kuhajda, H. Ayoub, and K. Ahmed, African-American hair: Its physical properties and differences relative to Caucasian hair, Cosmet. Toil., 110, 39–48 (1995). (8) A. Franbourg, P. Hallegot, F. Baltenneck, et al., Current reseach on ethnic hair, J. Am. Acad. Dermatol., 48, S115–S119 (2003). (9) L. J. Wolfram, Human hair: A unique physicochemical composite, J. Am. Acad. Dermatol., 48, S106– S114 (2003). (10) C. R. Robbins, Chemical and Physical Behavior of Human Hair (Spinger-Verlag, New York, 1988), Vol. 4. (11) C. Porter, S. Diridollou, and V. H. Barbosa, The infl uence of African-American hair’s curl pattern on its mechanical properties, Int. J. Dermatol., 44 (Suppl. 1) 4–5 (2005). (12) S. Nagase, M. Tsuchiya, T. Matsui, et al., Characterization of curved hair of Japanese women with refer- ence to internal structures and amino acid composition, J. Cosmet. Sci., 59, 317–332 (2008). (13) J. Menkart, L. J. Wolfram, and I. Mao, Caucasian hair, Negro hair, and wool: Similarities and differ- ences, J. Soc. Cosmet. Chem., 17, 769–787 (1966). (14) D. Hrdy, Quantitative hair form variation in seven populations, J. Phys. Anthrop., 39, 7–17 (1973). (15) Y. K. Kamath, S. Hornby, and H. D. Weigmann, Mechanical and fractographic behavior of Negroid hair, J. Soc. Cosmet. Chem., 35, 21–43 (1984). (16) Y. K. Kamath, S. Hornby, and H. D. Weigmann, Effect of chemical and humectant treatments on the mechanical and fractographic behavior of Negroid hair, J. Soc. Cosmet. Chem., 36, 39–52 (1985). (17) M. Feughelman, Mechanical Properties & Structure of Alpha-Keratin Fibers (UNSW Sydney Press, 1997). (18) N. I. Khumalo, P. T. Doe, R. F. Dawber, et al., What is normal hair like? A light and scanning electron microscopic study, J. Am. Acad. Dermatol., 43, 814–820 (2000). (19) B. Bernard, Hair shape of curly hair, J. Am. Acad. Dermatol., 48, S120–S126 (2003).

2008 TRI/PRINCETON CONFERENCE 109 (20) F. J. Wortmann and H. Deutz, Characterizing keratins using high-pressure differential scanning calo- rimetry (HPDSC), J. Appl. Polym. Sci., 48, 137–150 (1993). (21) J. M. Quadfl ieg Fundamental properties of Afro-American hair as related to their straightening, relax- ing behaviour, (vorgelegt von Fakultät für Mathematik, Informatik and Naturwissenschaften, Disserta- tion, 2003). (22) J. Wolberg, Data Analysis Using the Method of Least Squares: Extracting the Most Information from Experi- ments (Springer, 2005). (23) D. B. Duncan, Multiple range and multiple F tests, Biometrics, 11, 1–42 (1955). (24) Lehmann and H. Scheffe, Completeness, similar regions and unbiased estimation, Part II, Sankhya, 15, 219–236 (1955). (25) Student, The probable error of a mean, Biometrika, 6, 1–25 (1908). (26) R. A. Fisher, Applications of Student’s distribution, Metron, 5, 90–104 (1925). (27) H. Levene, Contributions to Probability and Statistics: Essays in Honor of Harold Hotelling, I. Olkin et al., Eds. (Stanford University Press, 1960), pp. 278–292. (28) R. A. Fisher, Statistical Methods for Research Workers (1925). (29) M. B. Brown and A. B. Forsythe, Robust tests for equality of variances, J. Amer. Stat. Assoc., 69, 364– 367 (1974). (30) F. J. Wortmann, G. Sendelbach, and Popescu, Fundamental DSC investigations of α-keratinous materi- als as basis for the interpretation of specifi c effects of chemical, cosmetic treatments on human hair, J. Cosmet. Sci., 58, 311–317 (2007). (31) J. M. Marsh, C. J. Clarke, K. Meinert, and R. M. Dahlgren, High pressure differential scanning calo- rimetry of colorant products, J. Cosmet. Sci., 58, 621–627 (2007). (32) A. Nagai, H. Komoriya, Y. Bunai, et al. Effect of hair dyes and bleach on the hair protein patterns as revealed by isoelectric focusing, Electrophoresis, 12, 451–453 (1991). (33) S. L. Khawar, K. Watson, and G. L. Jones, High resolution one-dimensional electrophoretic separation and partial characterization of human head hair proteins, Electrophoresis, 16, 110–115 (1995). (34) C. Nappe and M. Kermici, Electrophoretic analysis of alkylated proteins of human hair from various ethnic groups, J. Soc. Cosmet. Chem. 40, 91–99 (1989).