JOURNAL OF COSMETIC SCIENCE 358 (70:30, v/v) for 6 h. In each procedure, 3 g of hair was treated with 250 ml of solvent in the Soxhlet extractor. MECHANICAL COMBING MEASUREMENTS Combing analysis was achieved using a miniature tensile tester (Model 170), manufac- tured by Dia-Stron, Ltd., Hampshire, United Kingdom. The combing measurements were carried out on wet and dry hair with the following instrumental parameters: range, 2000 G gauge, 2 G size, 50 mm phase 1 (extension), 350% phase 2, 0% phase 3, 0% and phase 4, 0%. In all experiments, hair tresses were combed several times to remove entanglements before performing combing measurements. DYNAMIC CONTACT ANALYSIS A Thermo Cahn Dynamic Contact Angle Analyzer, DCA-322 (Thermo Fisher Scientifi c, Waltham, MA), was used to determine contact angle. A single dry hair fi ber, cut to ap- proximately 1 cm, was immersed in deionized water approximately 2–4 mm and the advancing contact angle was measured (inserted tip end fi rst). Fibers were obtained from the middle of a hair tress assembly ensuring that a straight section of fi ber was sampled. The required hair diameters were measured using a laser micrometer (Mitutoyo, model LSM-5000) purchased from Dia-Stron, Ltd. Twenty fi bers each for virgin and delipidized hair were measured. ATOMIC FORCE MICROSCOPY Atomic force microscopy (AFM) studies were conducted using a Digital Instruments Nanoprobe III Multimode SPM manufactured by Veeco Instruments (Santa Barbara, CA). Two modes of analysis, AFM and lateral force microscopy (LFM), were carried out in the contact mode. An AFM/LFM probe head was used in conjunction with a 100 μm piezoelectric scanner. The instrument used is a “beam bounce” type in which a diode laser beam is focused on to the back (top) of the cantilever. Commercial AFM probes (silicon tip on nitride lever, model SNL-10) were purchased from Veeco. Three-dimensional to- pography, error signal, and lateral force images were generated and analyzed with the instrument software (NanoScope Software, Veeco, Santa Barbara, CA). FTIR SPECTROSCOPIC IMAGING A 1-cm-long hair bundle was cut from the middle of Asian hair tresses and mounted on the top of a sample holder by embedding in ice. The hair bundle was then microtomed at -30°C into 5 μm thick cross sections with a Leica CM 1850 cryostat (Leica Microsystems, Inc., Bannockburn, IL). Hair cross sections were collected onto CaF2 windows for IR imaging. This preparation technique avoids any possibility of contamination with embedding or fi x- ing medium. Hair cross sections were imaged with a Perkin Elmer Spotlight system that couples an FTIR spectrometer with an optical microscope. The system consists of a linear

PHYSICOCHEMICAL PROPERTIES OF DELIPIDIZED HAIR 359 array of mercury-cadmium-telluride detector and an automated high precision XY sample stage. Images were acquired with 6.25 μm step size, 8 scans for each spectrum and 8 cm-1 spectral resolution. IR spectra were analyzed using ISys 3.1 software (6). DIFFERENTIAL SCANNING CALORIMETRY A Q2000 differential scanning calorimeter (TA Instruments, New Castle, DE) was used with pressure resistant, high-volume stainless steel pans. Samples consisted of 8 to 12 mg of cut (2–5 mm) hair fi bers, along with roughly 55 (±1.5) mg of deionized water. Each pan was sealed and allowed to sit for at least 6 h at room temperature to insure equi- librium water content and distribution within the hair fi bers. Heating at a rate of 2°C was performed from 22 to 190°C in standard mode. Three repetitions per lot were con- ducted. TA Universal Analysis 2000 for Windows software, version 4.7A, was used to determine the denaturation temperature (Td) and the enthalpy of denaturation (ΔH). Peak integrations were performed using the sigmoidal horizontal method, with the left marker staked at 110°C and the right positioned in the middle of the post-transition fl at baseline section (typically just below 150°C). TENSILE STRENGTH An Instron (model 3345) universal testing system for compression and tension, manufac- tured by Instron (Norwood, MA), was used for tensile strength measurements. The in- strument was equipped with a 100 N capacity force transducer (model 2519-103) and pneumatic grips (250 N capacity) with rubber-coated jaws capable of holding single hair fi bers. Each fi ber was mounted with metal and the samples were extended at a rate of 25 mm/min with data acquisition set at 100 Hz. Before tensile strength measurements, fi ber diameters were determined with a laser micrometer (Mitutoyo, model LSM-5000) purchased from Dia-Stron, Ltd. DYNAMIC VAPOR SORPTION ANALYSIS A DVS Advantage-1 gravimetric vapor sorption analyzer from Surface Measurement Sys- tems (Alperton, Middlesex, United Kingdom) was used. Hair samples consisted of ap- proximately 25 fi bers tied into a small loop weighing approximately 5 mg. The average diameter of the fi bers of each sample was determined using a Mitutoyo laser micrometer (Dia-Stron, Ltd.). Samples were subjected to 0–90% RH at 25°C in steps of 10% RH followed by 90–0% RH in steps of 10% RH. Each sorption/desorption step was 8 h in duration. Data were analyzed using DVS Standard Analysis Suite V6.1.1, DVS Advanced Analysis Suite V6.1.1, and Isotherm Analysis Suite V2.1.1. MECHANICAL ANALYSIS OF HAIR-SHAPED OMEGA LOOPS The instrumentation and experimental procedures were similar to those used in previous work (7). In brief, omega loop hair tresses were constructed by gluing both ends of the hair