Abstracts: Modeling the time‐dependent water wave stability of human hair

Abstract

by microfluorometric scanning that the negative charges generated in the cuticle surface can be used to bind low-molecularweight quaternary conditioners. This process can be considered as 'relipidation' or 'refatting of the scale faces. We have shown in earlier studies (1) that this entire process of oxidation-induced 'delipidation' and subsequent 'relipidation' of the acidic scale faces with a cationic conditioning molecule can also be reliably quantified by X-ray photoelectron spectroscopy (XPS). Furthermore, single-fiber wettability scanning using the Wilhelmy technique, which is highly sensitive to any changes in surface chemistry, is well-suited to detect and characterize treatmentinduced changes in the chemical nature of the hair surface from hydrophobic to hydrophilic.pp. 13-22 Natural moisturizing factors in the stratum corneum I. Effects of lipid extraction and soaking (M.V., A.L.R) Natural moisturizing factor (NMF) is essential for appropriate stratum corneum hydration, barrier homeostasis, desquamation, and plasticity. It is formed from filaggrin proteolysis to small, hygroscopic molecules including amino acids. We hypothesized that common lipid extraction and soaking in water would alter the level of NMF in the upper stratum corneum (SC) and its biophysical properties. A novel method of measuring and quantifying the amino acid components of NMF is presented. Adhesive tapes were used to collect samples of the SC and were extracted with 6 mM perchloric acid for analysis by reverse-phase highperformance liquid chromatography (HPLC).The HPLC results were standardized to the amount of protein removed by the tapes. An increase in NMF was found with increased SC depth. Also, the combination of extraction and soaking was found to increase NMF loss relative to control or to extraction or soaking alone. Our results indicate that common skin care practices significantly influence the water binding materials in the upper SC. The findings have implications for the evaluation and formulation of skin care products.pp. 23-29 Natural moisturizing factors in the stratum corneum II. Regeneration of NMF over time after soaking (M.V., A.L.R) The detrimental effects of prolonged water exposure on skin are well known. Information on the effects of short-term exposure, e.g. during bathing, showering, and hand washing, on Natural moisturizing factors (NMF) levels is limited. In an attempt to isolate the effects of soaking on the NMF, a time course for skin sample collection was devised in which adhesive tapes were applied 0.5 and 4 h after soaking of the treated arm. Significant decreases in NMF levels, quantified by high-performance liquid chromatography analysis of serial tape strips, were observed 0.5 h after soaking, with a replacement of NMF occurring by the four-hour mark. This replacement corresponds to a parallel rebound in skin pH also observed at these times. Stratum corneum (SC) hydration values, measured instrumentally as the rate of moisture accumulation (MAT), however, were depressed 0.5 h post-soaking and remai...

Perm-waved human hair: a thermorheologically complex shape memory composite

“…Hair loops were treated on a cylindrical roller and then cut to measure the remaining bending deformation. This is a convenient measure of the efficiency of a permanent or non-permanent waving treatment with a close proximity to the practical situation (8,30,31,32).…”

“…Care was taken to wind the hairs such that their axis was normal to the cylinder axis. Due to the ratio of hair vs cylinder diameter (max 100 μm vs 12 mm), shear strains in the fibre are well below the limits of linear viscoelasticity (< 1%) (10,32). The cylinder was then immersed in water for 30 min (20°C) to allow complete stress relaxation.…”

“…Against this background, the time-dependent recovery from permanent set, Rec(t), is assumed to be controlled by the general principles of linear viscoelasticity (5). The core principle is the interaction of the bending rigidities of the straight and the bent hair state according to Denby's equation, as an approximation of the Boltzmann Superposition Principle (6,8,24,30,32). We formulate Denby's (6) equation as (8,30,31):…”

“…Building on the suggested analogy between cohesive and permanent set, the relaxation functions are both a priori , but plausibly (8,32) expected to conform to the well-known and widely used Kohlrausch-Williams-Watt (KWW) function (46,47,48,49,50) as:…”

Shape of a Ponytail and the Statistical Physics of Hair Fiber Bundles

“…Whilst some of this is undoubtedly due to gravity (recall ≈ 5 cm), the major part is intrinsic, as we have verified by examining inverted hairs. This is in part due to the preparation process: after washing and rinsing, the hairs in a drying ponytail pass through a glass transition with decreasing humidity [1], locking in the intrinsic curvature [10], which is naturally reduced in the vicinity of the clamp due to confinement by neighboring filaments. Although this is something of a complication when it comes to interpreting the results, we must regard it as an essential feature of hair switches and ponytails comprised of real fibers.…”