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Notes: Synopsis The UVA protection delivered by sunscreens is an issue of increasing importance due to the increasing knowledge about UVA-induced skin damage. In Europe there is no officially accepted method available to determine the degree of UVA protection. Therefore, the objective of the present study was to design a protocol combining the merits of an in vitro model, which are simple and reproducible, with aspects known to be relevant from in vivo studies. The principle is: an UV-transparent support to which the test product is applied, a (pre)irradiation and a transmission measurement. Transpore® tape (standard support for SPF determinations) was found to be incompatible with many preparations on prolonged contact times. Roughened quartz was adopted as a suitable alternative. Transmission measurements on this support are not reliable with a layer of 2 mg cm−2 (standard for SPF) due to detection limitations of spectrophotometers, hence a reduced layer of 0.75 mg cm−2 was adopted. Overall, it is very difficult to apply products in a reproducible thin layer on appropriate substrates. As a consequence, absolute parameters derived from the transmission profile show relatively large dispersion, whereas relative parameters, such as critical wavelength λc[1] or UVA/UVB ratio are much less sensitive to unavoidable variations in layer thickness. An increase in deviations was observed when the samples were irradiated before measurement. It is crucial to control the output carefully (spectral distribution and even more importantly, irradiance and dose delivered) of the light source. By doing so and also taking into account the previous learning steps, a protocol was drafted and tested in a ringtest (four samples in six laboratories). The results are encouraging and show that if relative parameters (e.g. λc, UVA/UVB ratio) are considered, the intra- as well as interlaboratory reproducibility is clearly better than can be obtained in vivo.In general, we describe a suitable method, which can be considered in any future official discussions about the methodology to determine UVA protection. Résumé La protection contre les UVA apportée par les écrans solaires est un sujet d’importance croissante en raison de la progression des connaissances concernant les dommages à la peau causés par les UVA. En Europe il n’existe pas de méthode disponible officiellement reconnue pour déterminer le degré de protection contre les UVA. Par conséquent, l’objectif de la présente étude est de concevoir un protocole associant les avantages d’un modèle in vitro, qui est simple et reproductible, avec des aspects connus comme appartenant aux études in vivo. Le principe est le suivant: un support transparent aux UV auquel le produit testé est appliqué, une (pré)irradiation et une mesure de transmission. Le ruban Transpore® (support standard pour la détermination des SPF) se révèle incompatible avec de nombreuses préparations lors de temps de contact prolongés. Le quartz rugueux est adopté comme alternative appropriée. Les mesures de transmission sur ce support ne sont pas fiables avec une couche de 2 mg/cm2 (norme pour les SPF) en raison des limites de détection des spectrophotomètres, et on adopte donc une couche réduite de 0,75 mg/cm2. Il est surtout très difficile d’appliquer des produits en une couche fine reproductible sur des substrats appropriés. En conséquence, les paramètres absolus tirés du profil de transmission montrent une assez grande dispersion, tandis que les paramètres relatifs, tels que la longueur d’onde critique λc[l] ou le rapport UVA/UVB sont beaucoup moins sensibles aux variations inévitables de l’épaisseur de la couche. On observe une augmentation des écarts lorsque les échantillons sont irradiés avant la mesure. Il est crucial de contrôler soigneusement la sortie (distribution spectrale et encore plus important, irradiation et dose délivrée) de la source lumineuse. Dans ces conditions, et en tenant aussi compte des enseignements des étapes précédentes, un protocole a étéébauché et testé lors d’un essai tournant (quatre échantillons dans six laboratoires). Les résultats sont encourageants et montrent que si on considère les paramètres relatifs (par exemple λc, rapport UVA/UVB), la reproductibilité intra et interlaboratoires est clairement meilleures que ce qu’on peut obtenir in vivo.D’une façon générale, nous décrivons une méthode appropriée, qui peut être considérée dans tout échange officiel futur concernant la méthodologie pour déterminer la protection contre les UVA.

Notes: Standardization of the method to determine sun protection factors (SPF) is fundamental to uniform labelling of SPF values on sun products. The COLIPA Task Force ‘Sun Protection Measurement’(SPM), including representatives of major European sun-product manufacturers and contract testing laboratories, was established in 1990 to define methods for sun products testing. The process involved in developing the COLlPA SPF Test Method started with a critical appraisal of previously existing methods, and identification of areas for improvement. Experiments were performed by the participating laboratories to establish the new recommended test protocol which was then confirmed in two multicentred ring tests. Improvements to test methodology included the number and selection of volunteers and skin types, the application of the product, the definition of W output from solar simulators, and the method for assessing erythemal response (MED) including an option to use colorimetry to define objectively the ‘erythemal threshold’ of skin and to predetermine MED prior to exposure. Four cosmetic formulations and neutral density physical filters (SPF from 4 to 20) were tested in two ring tests. Results showed that variations in SPF of the cosmetic products were, on average, directly proportional to SPF value. An excellent correlation was found between visual and colorimetric SPF assessments (r = 0.99). An acceptable range of values for low and high SPF standard products was also established. The COLIPA SPF test method is now fully defined and supported by experimental data. Its use will harmonize SPF testing throughout Europe and help in the quest for global harmonization in testing sun products.

Notes: In this article we report on the temperature dependencies of the longitudinal and shear sound velocities in Ti4AlN3, Ti3Al1.1C1.8, and Ti3SiC2. The velocities are measured using a phase sensitive pulse-echo ultrasonic technique in the 90–300 K temperature range. At room temperature, Young's, ERT, and shear, μRT, moduli and Poisson's ratio of Ti4AlN3 are 310±2, 127±2 GPa, and 0.22, respectively. The corresponding values for Ti3AlC2 are 297.5±2, 124±2 GPa, and 0.2. Both moduli increase slowly with decreasing temperature and plateau out at temperatures below (approximate)125 K. A least squares fit of the temperature dependencies of the shear and Young's moduli of Ti4AlN3 yield: μ/μRT=1−1.5×10−4(T−298), and E/ERT=1−0.74×10−4(T−298), for T〉125 K. The corresponding relationships for Ti3Al1.1C1.8 are: μ/μRT=1−1.2×10−4(T−298), and E/ERT=1−0.84×10−4(T−298) for T〉125 K. The acoustic Debye temperatures calculated for Ti4AlN3 and Ti3AlC2, as well as Ti3SiC2, are all above 700 K, in agreement with values calculated from low temperature heat capacity measurements. © 2000 American Institute of Physics.

Notes: In this work, the Young's, E, and shear, μ, moduli of Ti3SiC2 are measured ultrasonically in the 20–300 K temperature range. At room temperature, Young's, ERT, and shear, μRT, moduli are 322±2 and 133.6±0.8 GPa, respectively. Poisson's ratio is 0.2. Both moduli increase slowly with decreasing temperature and plateau out at temperatures below (approximate)130 K. A least square fit of the data yields, μ/μRT=1−1.42×10−4(T−298) and E/ERT=1−0.95×10−4(T−298) for temperatures greater than 140 K. The elastic Debye temperature is estimated to be 427 K, which is significantly lower than the value of 620 K calculated from heat capacity measurements. © 1999 American Institute of Physics.

Notes: Despite vast differences in their other properties, the responses of Ti3SiC2 and ice to stress are quite similar in that they are quite strain-rate sensitive; if loaded rapidly, both are brittle, but if loaded slowly they are quite plastic. This stems from the fact that both are plastically very anisotropic; deformation occurs overwhelmingly, if not exclusively, by slip along basal planes. In both cases, stress concentrations and the rate at which they are relaxed dictate the nature of the mechanical response. In the brittle regime, microcracks and their linkage play a dominant role in both cases. © 2001 American Institute of Physics.