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- 2019
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Tidskriftsartikel (refereegranskat)
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- Álvarez-Asencio, Rubén, et al.
(författare)
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Nanomechanical properties of human skin and introduction of a novel hair indenter
- 2016
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Ingår i: Journal of The Mechanical Behavior of Biomedical Materials. - : Elsevier. - 1751-6161 .- 1878-0180. ; 54, s. 185-193
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Tidskriftsartikel (refereegranskat)abstract
- The mechanical resistance of the stratum corneum, the outermost layer of skin, to deformation has been evaluated at different length scales using Atomic Force Microscopy. Nanomechanical surface mapping was first conducted using a sharp silicon tip and revealed that Young’s modulus of the stratum corneum varied over the surface with a mean value of about 0.4 GPa. Force indentation measurements showed permanent deformation of the skin surface only at high applied loads (above 4 μN). The latter effect was further demonstrated using nanomechanical imaging in which the obtained depth profiles clearly illustrate the effects of increased normal force on the elastic/plastic surface deformation. Force measurements utilizing the single hair fiber probe supported the nanoindentation results of the stratum corneum being highly elastic at the nanoscale, but revealed that the lateral scale of the deformation determines the effective elastic modulus.This result resolves the fact that the reported values in the literature vary greatly and will help to understand the biophysics of the interaction of razor cut hairs that curl back during growth and interact with the skin.
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- Besharat, Zahra, et al.
(författare)
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Mixed monolayers of alkane thiols with polar terminal group on gold : Investigation of structure dependent surface properties
- 2016
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 484, s. 279-290
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Tidskriftsartikel (refereegranskat)abstract
- Adsorption of thiols with cationic or anionic terminal group on gold has been studied from mixed solutions of 11-Amino-1-undecanethiol (AUT) and 3-Mercaptopropionic acid (MPA) using Quartz Crystal Microbalance with Dissipation (QCM-D), X-ray Photoelectron Spectroscopy (XPS), atomic force microscopy (AFM) and contact angles. The goal is to probe the nature of such layers, and the additivity or otherwise of the pH responsiveness, with a view to evaluate their suitability as smart materials. For each of the two pure (unmixed) cases, ordered molecular monolayers are formed with sulfur binding to gold and the alkane chain pointing out from the surface as expected. Adsorption from the thiol mixtures, however, leads to a more complex behaviour. The surface concentration of thiols from the mixtures, as determined by QCM-D, is considerably lower than for the pure cases and it reaches a minimum at a 3:1 MPA/AUT relative concentration in the solution. The XPS results confirm a reduction in adsorbed amount in mixtures with the lowest overall intensity for the 3:1 ratio. Monolayers formed from mixtures display a wettability which is much lower and less pH sensitive. Collectively these results confirm that for adsorption from mixed systems, the configuration is completely different. Complex formation in the mixed solutions leads to the adsorption of molecules parallel to the surface in an axially in-plane configuration. This parallel layer of thiols is mechanically relatively robust to nano-shaving based on AFM measurements. These results will have a significant impact on the design of biomimetic surface coatings particularly when mixtures of oppositely charged molecules are present on the surface, as is commonly the case in biological, proteinaceous surfaces (e.g. hair and skin).
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- Pastorelli, Concetta, et al.
(författare)
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Positive parenting and children’s prosocial behavior in eight countries
- 2016
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Ingår i: Journal of Child Psychology and Psychiatry. - : Wiley. - 0021-9630 .- 1469-7610. ; 57:7, s. 824-834
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Tidskriftsartikel (refereegranskat)abstract
- Background Research supports the beneficial role of prosocial behaviors on children’s adjustment and successful youth development. Empirical studies point to reciprocal relations between negative parenting and children’s maladjustment, but reciprocal relations between positive parenting and children’s prosocial behavior are understudied. In this study reciprocal relations between two different dimensions of positive parenting (quality of the mother–child relationship and the use of balanced positive discipline) and children’s prosocial behavior were examined in Colombia, Italy, Jordan, Kenya, the Philippines, Sweden, Thailand, and the United States. Methods Mother–child dyads (N = 1105) provided data over 2 years in two waves (Mage of child in wave 1 = 9.31 years, SD = 0.73; 50% female). Results A model of reciprocal relations between parenting dimensions, but not among parenting and children’s prosocial behavior, emerged. In particular, children with higher levels of prosocial behavior at age 9 elicited higher levels of mother–child relationship quality in the following year. Conclusions Findings yielded similar relations across countries, evidencing that being prosocial in late childhood contributes to some degree to the enhancement of a nurturing and involved mother–child relationship in countries that vary widely on sociodemographic profiles and psychological characteristics. Policy and intervention implications of this study are discussed.
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- Sjövall, Peter, et al.
(författare)
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Imaging the distribution of skin lipids and topically applied compounds in human skin using mass spectrometry
- 2018
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- The barrier functions of skin against water loss, microbial invasion and penetration of xenobiotics rely, in part, on the spatial distribution of the biomolecular constituents in the skin structure, particularly its horny layer (stratum corneum). However, all skin layers are important to describe normal and dysfunctional skin conditions, and to develop adapted therapies or skin care products. In this work, time-of-flight secondary ion mass spectrometry (ToF-SIMS) combined with scanning electron microscopy (SEM) was used to image the spatial distribution of a variety of molecular species, from stratum corneum down to dermis, in cross-section samples of human abdominal skin. The results demonstrate the expected localization of ceramide and saturated long-chain fatty acids in stratum corneum (SC) and cholesterol sulfate in the upper part of the viable epidermis. The localization of exogenous compounds is demonstrated by the detection and imaging of carvacrol (a constituent of oregano or thyme essential oil) and ceramide, after topical application onto ex vivo human skin. Carvacrol showed pronounced accumulation to triglyceride-containing structures in the deeper parts of dermis. In contrast, the exogenous ceramide was found to be localized in SC. Furthermore, the complementary character of this approach with classical ex vivo skin absorption analysis methods is demonstrated.
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- Skedung, Lisa, et al.
(författare)
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Mechanisms of tactile sensory deterioration amongst the elderly
- 2018
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- It is known that roughness-smoothness, hardness-softness, stickiness-slipperiness and warm-cold are predominant perceptual dimensions in macro-, micro- and nano- texture perception. However, it is not clear to what extent active tactile texture discrimination remains intact with age. The general decrease in tactile ability induces physical and emotional dysfunction in elderly, and has increasing significance for an aging population. We report a method to quantify tactile acuity based on blinded active exploration of systematically varying micro-textured surfaces and a same-different paradigm. It reveals that elderly participants show significantly reduced fine texture discrimination ability. The elderly group also displays statistically lower finger friction coefficient, moisture and elasticity, suggesting a link. However, a subpopulation of the elderly retains discrimination ability irrespective of cutaneous condition and this can be related to a higher density of somatosensory receptors on the finger pads. Skin tribology is thus not the primary reason for decline of tactile discrimination with age. The remediation of cutaneous properties through rehydration, however leads to a significantly improved tactile acuity. This indicates unambiguously that neurological tactile loss can be temporarily compensated by restoring the cutaneous contact mechanics. Such mechanical restoration of tactile ability has the potential to increase the quality of life in elderly.
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