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Selected AbstractsIn vitro testing to assess the UVA protection performance of sun care productsINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 1 2001Applied Cosmetics) Task Force, Members of the DGK (German Society for Scientific, Sun Protection'. 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 ,c[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. ,c, 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 ,c[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 ,c, 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. [source] Concurrent Q-learning: Reinforcement learning for dynamic goals and environmentsINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 10 2005Robert B. Ollington This article presents a powerful new algorithm for reinforcement learning in problems where the goals and also the environment may change. The algorithm is completely goal independent, allowing the mechanics of the environment to be learned independently of the task that is being undertaken. Conventional reinforcement learning techniques, such as Q-learning, are goal dependent. When the goal or reward conditions change, previous learning interferes with the new task that is being learned, resulting in very poor performance. Previously, the Concurrent Q-Learning algorithm was developed, based on Watkin's Q-learning, which learns the relative proximity of all states simultaneously. This learning is completely independent of the reward experienced at those states and, through a simple action selection strategy, may be applied to any given reward structure. Here it is shown that the extra information obtained may be used to replace the eligibility traces of Watkin's Q-learning, allowing many more value updates to be made at each time step. The new algorithm is compared to the previous version and also to DG-learning in tasks involving changing goals and environments. The new algorithm is shown to perform significantly better than these alternatives, especially in situations involving novel obstructions. The algorithm adapts quickly and intelligently to changes in both the environment and reward structure, and does not suffer interference from training undertaken prior to those changes. © 2005 Wiley Periodicals, Inc. Int J Int Syst 20: 1037,1052, 2005. [source] Robustness of time-scale learning of robot motions to uncertainty in acquired knowledgeJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 10 2001C.C. Cheah A disadvantage of present iterative learning control algorithms is that they are generally applicable only in cases where a certain task is performed over and over again. Consequently, if knowledge or control inputs acquired from learning a task can be used on similar tasks, learning will be more efficient. Recently, several methods for constructing the control input of a new motion based on the control inputs acquired from previous learning of similar tasks have been proposed. However, these methods assumed that the perfect control inputs could be obtained from the previous learning. In practice, the control inputs could never be obtained exactly from learning in the presence of certain uncertainties such as disturbance and measurement noises. In addition, it is also not known for sure how the basic motion patterns should be chosen for learning. In this article, the robustness problem of the time-scale learning control to uncertainty in the acquired learning control inputs is formulated and solved. From the analysis, certain new insights such as its implication to choices of basic motion patterns for time-scale learning will be discussed. Simulation results of a 3-link robot are presented to illustrate the analysis. © 2001 John Wiley & Sons, Inc. [source] Intermanual transfer of a new writing occupation in young adults without disabilityOCCUPATIONAL THERAPY INTERNATIONAL, Issue 1 2002Megan E. Andree Abstract It has been shown that acquisition of a skill by one hand is facilitated by previous learning of the same skill with the other hand. This is called intermanual transfer of learning, or cross-education. The investigators examined intermanual transfer of occupation of writing in a group of 10 right-handed subjects with no known motor disabilities. Subjects learned to perform a novel occupation of writing a foreign alphabet letter with either their right or left hand. Later, subjects reproduced the skill with the practised and unpractised contralateral hand. Pen movements and surface electromyography of the first dorsal interosseus muscle were recorded to assess the transfer of learning. Analysis revealed an almost full transfer of the learned motor task between hands in either left-to-right or right-to-left direction when movement time and movement size were compared. This indicates that transfer did not depend on hand dominance. These findings suggest that a task already learned by one hand can positively influence the learning of the same task by the other hand. The results have important implications for occupational therapy , namely, that activities comprising tasks previously learned by one hand would be more effective in facilitating improved performance by the other hand than activities comprising previously unlearned tasks in the case of retraining skills in patients with amputation or hemiplegia. Because the participants in this study were a small number of college students, research should be carried out with larger participant pools and participants with disabilities to consolidate the findings. Copyright © 2002 Whurr Publishers Ltd. [source] | ||||||||||