Mechanical Properties Of Hair Research Articles

The Effect of Supplemental Lighting during the Late Gestation Period on Post-Partum Mechanical Properties of Mare and Foal Guard Hair.

This study investigates Thoroughbred mares exposed or not to supplemental blue light at the end of the gestation. Sixty mares and their 60 foals were selected for the investigation. Guard hair samples were collected from the shoulder just after (within 12 h) the parturition or birth. The foals of the light-treated mares developed significantly (p < 0.05) shorter hair than those of the control mares. A general effect of light treatment on basal hair diameter thinning could be demonstrated (p < 0.005). The maximum force of hair samples of light-treated mares and foals (0.098 and 0.085 N, respectively) was significantly lower than that of the control (0.272 and 0.178 N, respectively). The tensile strength (82.2 N/mm2) of the foal hair samples of the light-treated mares was significantly lower than that of the control foals (121.6 N/mm2). Although no significant difference was found in the elongation (ΔL), the hair of the control animals (mares and foals together) was more elastic than that of the treated animals (335 vs. 262 μm). In conclusion, the supplemental blue light treatment of the pregnant mares has a decreasing effect on both mares and their foals on the mechanical properties of the hair, making it shorter, thinner, and weaker.

Integrative measurement analysis via machine learning descriptor selection for investigating physical properties of biopolymers in hairs

Integrative measurement analysis of complex subjects, such as polymers is a major challenge to obtain comprehensive understanding of the properties. In this study, we describe analytical strategies to extract and selectively associate compositional information measured by multiple analytical techniques, aiming to reveal their relationships with physical properties of biopolymers derived from hair. Hair samples were analyzed by multiple techniques, including solid-state nuclear magnetic resonance (NMR), time-domain NMR, Fourier transform infrared spectroscopy, and thermogravimetric and differential thermal analysis. The measured data were processed by different processing techniques, such as spectral differentiation and deconvolution, and then converted into a variety of “measurement descriptors” with different compositional information. The descriptors were associated with the mechanical properties of hair by constructing prediction models using machine learning algorithms. Herein, the stepwise model refinement via selection of adopted descriptors based on importance evaluation identified the most contributive descriptors, which provided an integrative interpretation about the compositional factors, such as α-helix keratins in cortex; and bounded water and thermal resistant components in cuticle. These results demonstrated the efficacy of the present strategy to generate and select descriptors from manifold measured data for investigating the nature of sophisticated subjects, such as hair.

On the Strength of Hair across Species

Summary The hair of mammals varies in diameter across species from ∼60 μm in humans to over ∼400 μm in giraffes and elephants. Here, we establish that the tensile strength of hair generally decreases with increasing diameter. Although there is a commonality in the morphology of the hair in such differing species as they all possess a cortex surrounded by cuticles, there are also significant differences in the hierarchical structure that contribute to the observed differences in strength. In this work, the internal structure of the hair from different species is examined, with some unique peculiarities in javelina and capybara hair uncovered. The dimensional dependence of hair strength is compared using Weibull predictions. The good correlation of the strength of hair using such Weibull analysis suggests that the failure strength is dictated by the probability distribution of flaws within the cortex.

Nanoindentation of Hair Cortex and Medulla Regions

Reports related to cuticle damage and hair’s mechanical properties are of interest to dermatologists in treatment of hair disorders. Apart from tensile test, few studies were reported on mechanical properties of hair, especially nanomechanical properties of cortex and medulla regions. Inner diameter of hair fiber (8–12 µm) is considered as medulla and it exists in hair at the beginning of the anagen phase. This study is aimed for quantitative comparison of nanomechanical properties between cortex and medulla and also with respect to donor age by performing nanoindentation on fiber cross sections using two different instruments. The medulla and cortex regions revealed hardness values of 70–170 MPa and 200–312 MPa, respectively. Similarly lower values of indentation modulus were observed for medulla compared to cortex because medulla has poorer orientation of microfibrils compared to the surrounding cortex. This study also found a linear correlation between hardness and indentation modulus especially for medulla region. This could be due to the fact that organization of the microfibrils increases from the medulla center to medulla periphery. It is also found that donor age has no influence on cortex modulus and hardness. The findings of this study will be useful for dermatologists in estimating the hair disorders and for estimating dye uptake of keratin fibers in textiles.

Influence of an Oral Supplementation Based on Orthosilicic Acid Choline-Stabilized on Skin, Hair and Nails: A Clinical Study with Objective Approach

In recent years, various dietary supplements have been released in the market with the promise of health benefits and functional properties. New trends involving nutrition have been highlighted due to the potential effects of certain food ingredients in the cutaneous aging process, the healthy appearance of skin, hair and nails. Looking at the growing demand for improvement in the appearance of hair, skin and nails and the increased interest of the population by use of nutricosmetics, the aim of this study was to evaluate an oral supplementation with orthossilicic acid choline-stabilized. For this, it was done a randomized, placebo-controlled clinical test. After approval of the ethics committee, were selected 60 women, aged 40 and 65 and they were divided into two groups (treatment and placebo). The daily dose of the supplement for evaluation was 400 mg of orthossilicic acid choline-stabilized for a period of 3 months. Analyzes were done before the treatment (basal-T0) and after 30, 60 and 90 days of treatment and it were evaluated the structural characteristics of the dermis, the mechanical properties of hair and the perception of effectiveness by the volunteers. According to the results, it was observed for the treatment group an increase in echogenicity of the dermis after 90 days of treatment. Thus, it proved that the treatment increased the density of the skin. In addition, the high resolution images showed improvement in skin micro relief and an improvement in skin roughness. There was also increased resistance of the hair and volunteers of treatment group reported improvement in skin, hair and nails. Finally, the oral supplementation of the nutricosmetic with orthossilicic acid choline-stabilized can be suggested as an effective product to increase skin density and to improve hair and nails conditions, complementary to topical treatments.

AFM studies of environmental effects on nanomechanical properties and cellular structure of human hair

Characterization of cellular structure and physical and mechanical properties of hair are essential to develop better cosmetic products and advance biological and cosmetic science. Although the morphology of the cellular structure of human hair has been traditionally investigated using scanning electron microscopy and transmission electron microscopy, these techniques provide limited capability to in situ study of the physical and mechanical properties of human hair in various environments. Atomic force microscopy (AFM) overcomes these problems and can be used for characterization in ambient conditions without requiring specific sample preparations and surface treatment. In this study, film thickness, adhesive forces and effective Young's modulus of various hair surfaces were measured at different environments (humidity and temperature) using force calibration plot technique with an AFM. Torsional resonance mode phase contrast images were also taken in order to characterize the morphology and cellular structure changes of human hair at different humidity. The correlation between the nanomechanical properties and the cellular structure of hair is discussed.

The JID Legacy Project: Introspecting on Our Past

A legacy is something you inherit from the past and can bequeath to the future. Our journal's legacy includes 66 years of publication, and back issues of the JID are now available online from 1970. What can we see from this portion of our history? It is beyond the quaintness of people struggling at the limits of their techniques and the overall concepts of the day. It is an appreciation that some of today's best research may have the same aura of naivete in the face of the complex biological processes under investigation when that literature is read from the perspective of our intellectual descendents 35 or 100 years from now. Is humility the coat in which striving, even successful, scientists of today should clothe themselves? Is musing over our past most appropriately the province of very senior, white-haired—or no-haired—researchers?

Investigating the relationship between the hair fiber proteome and hair quality

Many hair characteristics (e.g. color and curl) are genetically determined. Here, we investigated whether hair quality is also genetically controlled and related to differences in hair composition. Female, Caucasian subjects (n = 292) were recruited into this study and segmented by self-perceived hair quality and by permanent colorant usage. Hair fibers were collected and characterized by amino acid analysis, dry tensile elastic modulus testing and two-dimensional electrophoresis of hair protein extracts. Protein analysis revealed a string of 66 kDa proteins that correlated with hair of high quality. Loss of low molecular weight (14–29 kDa) proteins increased with colorant usage, particularly in hair of low quality. Amino acid analysis showed that the levels of serine and threonine across all the subjects followed bimodal frequency distributions suggestive of a genetic influence. Overall, data suggested that perception of quality was linked to high serine and threonine levels. In addition, where hair was colored, quality was associated with lower cysteic acid levels. Lower cysteic acid levels were not linked to lower colorant usage and our data suggest that high quality hair may be more resistant to colorant damage. Elastic modulus was significantly higher in hair of higher quality (4.65 GPa) compared to all medium and low quality hair combined (4.3 GPa), P < 0.02. This suggests a link between altered hair composition and mechanical properties. In conclusion, the composition and mechanical properties of hair have been linked to hair quality. We hypothesize that hair quality is thus likely to be genetically determined. Understanding of the links between hair composition and its properties could be utilized in the future for designing products targeted to each individual's hair make-up, and for producing diagnostic tools for determining hair quality.

Biophysical and biochemical studies of the hair in cartilage-hair hypoplasia.

The hair from four patients with classical cartilage‐hair hypoplasia (CHH) was studied with respect to its stress‐strain characteristics, amino acid composition, solubility in 6 M urea containing reducing agents, and the electrophoresis of the isolated S‐carboxymethylated proteins in acrylamide gels containing 6 M urea. Many CHH hairs had the mechanical properties of hairs with reduced disulfide bonds and these properties returned to normal after five minutes' oxidation with 3 % hydrogen peroxide, There was decreased solubility of CHH hair with a deficiency of the filamenlous proteins when 0.1 M mercaptocthanol was the reducing agent; with 0.1 M dithiothreitol as reducing agent, the yield of proteins increased and the electrophoretic pattern was normal. The filamentous and matrix proteins of CHH hair have no gross structural defects, and it is suggested that the decreased reactivity of some disulfide bonds may he responsible for the abnormal biophysical and biochemical characteristics of this hair.

Mechanical properties of hairs from patients with different types of hair diseases

The following mechanical properties of hair have been studied: tensile strength, strain at break, and elastic modulus. The determinations were made at constant temperature and humidity on fifty separate hairs from each patient. The mechanical properties of the fibrous material were similar for thick and thin hair. The elastic modulus and tensile strength showed a good correlation. Five patients with ectodermal dysplasia and one with congenital ichthyosiform erythrodermia had a lower elastic modulus than the other groups. Hair from those with ectodermal dysplasia also showed a low tensile strength. No significant difference in mechanical properties were found between normal-appearing hair and hair from patients with male pattern baldness, alopecia areata and various types of female defluvium capillorum.

Mechanical Properties of Hairs from Patients with Different Types of Hair Diseases

The following mechanical properties of hair have been studied: tensile strength, strain at break, and elastic modulus. The determinations were made at constant temperature and humidity on fifty separate hairs from each patient. The mechanical properties of the fibrous material were similar for thick and thin hair. The elastic modulus and tensile strength showed a good correlation. Five patients with ectodermal dysplasia and one with congenital ichthyosiform erythrodermia had a lower elastic modulus than the other groups. Hair from those with ectodermal dysplasia also showed a low tensile strength. No significant difference in mechanical properties were found between normal-appearing hair and hair from patients with male pattern baldness, alopecia areata and various types of female defluvium capillorum.