Ralf Hagens

Non‐invasive monitoring of oxidative skin stress by ultraweak photon emission measurement. II: biological validation on ultraviolet A‐stressed skin

Background/purpose: Several physical or chemical environmental stressors generate reactive oxygen species, which trigger oxidation reactions of cells or tissues and thereby induce a correlated ultraweak photon emission (UPE) signal. The present study was designed to qualify and validate UPE measurement following ultraviolet (UV) excitation of porcine and human skin as an analytical method to assess the potency of topical antioxidants in vivo.

Non-invasive monitoring of oxidative skin stress by ultraweak photon emission (UPE)-measurement. I: mechanisms of UPE of biological materials

Background/purpose: Oxidation of proteins and amino acids is associated with generation of ultraweak photon emission (UPE), which may be used to assess oxidative processes in the skin in a non‐invasive way. This first part of a series of reports addresses the physicochemical basis of oxidation‐induced UPE in the skin, with a special focus on the contribution of amino acid oxidation.

Contact angle measurement – a reliable supportive method for screening water‐resistance of ultraviolet‐protecting products in vivo

Substantivity of sunscreen formulations is affected by the wash‐out rate of ultraviolet‐absorber and ‐reflector compounds in water. Water‐resistance of sunscreen formulations is currently determined according to a standardized European Cosmetic Toiletry and Perfumery Association (COLIPA) protocol, encompassing the determination of a minimal erythemal dose before and after a defined immersion step in water. It can be supposed that the higher the wettability of a treated skin area, the higher is the wash‐out rate of sunscreen compounds. This present report addresses the validity of determining the wettability of treated skin alone as a measure for the water‐resistance of sunscreen products. The report addresses the robustness, accuracy and congruence of a recently developed wettability test, based on the measurement of the contact angle (CA) of a sessile water drop on treated skin areas. Contact angle data of 66 sunscreen formulations are compared with the corresponding results of 81 water‐resistance tests, using the sun protection factor (SPF)/immersion/SPF method. Sunscreen products tested by the CA method were applied to the skin of the volar forearm of test subjects at a defined dose and drying‐time, using a standardized application and recording device. Contact angles between a sessile water drop and skin were recorded by a Charge‐Coupled Device (CCD) camera and subjected to automatic contour analysis. Taking the SPF/immersion/SPF method as gold standard, accuracy parameters of the CA method were determined. By using an appropriate cut‐off level of CAs, the CA method has a specificity and positive‐predictive value of 100%, and turns out to be a reliable screening method to identify water‐resistant formulations. Based on our findings, those formulations that give CAs above 30° may be categorized water‐proof without further testing by the COLIPA water‐resistance method.

Conventional sunscreen application does not lead to sufficient body coverage

This study aimed to assess sunscreen application habits and relative body coverage after single whole body application.

Multi-view photometric stereo using surface deformation

This paper presents a hybrid approach for 3D reconstruction by fusing photometric stereo and multi-view stereo. The 3D surface is obtained by capturing a set of images taken from different viewpoints under time-varying illuminations. Key factors in the reconstruction process are surface normals that are obtained from photometric stereo. The surface is initialized by integrating the normals and then refined by performing iterative deformations on the initial surface and thereby optimizing image and normal consistency in multiple views. Benefiting from the employment of the deformation approach, we are able to perform image and normal consistency optimization without using matching windows. Instead, always the complete surface is back-projected. This makes the proposed approach much simpler and more robust compared to window-based approaches, which typically require global optimization with constraints on neighboring windows. Experiments on real-world data and ground-truth data show that for diffuse midsized objects without large depth discontinuities our approach improves the accuracy of the reconstructions compared to exiting approaches.

Towards a Body Hair Atlas of Women of Caucasian Ethnicity

A preliminary study was conducted in 17 female volunteers (mean age 29.8 years) to gain deeper insights into the characteristics of terminal Caucasian female body hair of different body parts. The focus on Caucasian women was driven by the high number of different scalp hair phenotypes in this ethnicity and intended to identify relevant differences between body areas to improve body hair removal approaches.